A Conversation on the CNPS-San Diego Listserv
Compiled by Mike Gonzales, Founding Member, San Diego Pollinator Alliance and Former Chairperson, CNPS-San Diego Garden Committee
Can restoring our yards into native urban gardens, albeit very difficult to do given the nature of urban yards, help San Diego’s endemic plants survive and thrive?
Believe me, I understand the part about not being easy! I’ve been stumbling around my front and back yards for 20+ years sluggishly transforming iceplant-covered slopes into some semblance of a native urban garden, or at least semi-native at this point. I thought Wayne Tyson was joking when he posted on the CNPS-SD listserv that, “it's as easy as duplicating the conditions [or functionally mimicking them] under which indigenous ecosystems function.” Well, maybe it was just tongue-in-cheek as he followed up with, “That can be difficult, but it's not impossible, especially the mimicking part [due to] the site conditions that one has to begin with, but it can be done.”
This post epitomizes the macrocosm of my ongoing quest-to create something that hopefully might be considered a decent foundation for, as Wayne puts it, “preserving indigenous germplasm while not sacrificing beauty or utility, and further minimizing the use of imported water and nutrients from other places.” I know, this certainly sounds like a lofty goal, but I’ve been having fun at it – thanks to all the wonderful information streaming across the list-serve from very knowledgeable people whose advice I deeply respect.
Ok, so if you don’t mind too much I’d like to take a slight detour here, as I feel I should at least try to understand what Wayne means when he refers to the term ‘germplasm’. I’m guessing it may have something to do with what both Wayne and Greg Rubin refer to as “the mycorrhizal net (i.e., the natural soil-crust community of algae, mosses, and other cryptobiotic/cryptogamic soil-crust plant communities[1] which are fireproof, erosion-protectors, and infiltration-facilitators).Symbiotic benefits of a mycorrhizal net include disease resistance, pest resistance, and increased availability of moisture. Absence of a mycorrhizal net (and many other microbial constituents of the indigenous microbiome) is a contributor to weed growth, as most weeds are not obligately mycorrhizal; in fact, their presence may inhibit their formation.”
Here's another great explanation of the ‘mycorrhizal net’ by Frank Landis:
“Arbuscular mycorrhizae started with liverworts, or rather their ancestors, and were likely essential for the first evolution of plants onto land. Mycorrhizal relationships pre-date the evolution of roots by millions of years as shown by fossils from the Rhynie Chert. It's worth remembering that every major clade in the plant kingdom, from liverworts on up, has produced non-mycorrhizal species, and some clades (such as mosses) are exclusively non-mycorrhizal. The direction of evolution in plants has been towards diversification of mycorrhizal syndromes (there are at least five known, of which arbuscular mycorrhizae are the most ancient), and, as I noted, loss of mycorrhizae, which has happened too many times to count. So, why lose mycorrhizae?
They take time and resources to form–very few short-lived annual plants have them.
They don't do well in low oxygen–very few aquatic plants have them, because underwater sediments are generally anoxic.
They may benefit a plant's competitors more–for example, many mustards produce toxins (mustard oils) in the soils around their roots to suppress the mycorrhizae working with their competitors.
There are other ways that some plants get nutrients out of the soil, such as the acids secreted by proteoid roots on Proteasand other plants, mycorrhizae just get in the way of these systems.
The fungi take a cut of the nutrients–depending on the circumstances, this may be so much that some plants are better off without the fungi, and they eject them from their roots.
Basically, mycorrhizal fungi are subcontractors in the field of nutrient acquisition for their partners-the plants. They trade nutrients (which they are good at getting out of the soil) for carbs (which plants are good at making through photosynthesis). As with any relationship, it may or may not be mutually beneficial in a particular environment at a particular time, and either partner may cheat or take advantage of the other. If you hear anybody saying that mycorrhizae are the solution to all your garden woes, translate that in your head to "subcontracting out aspects of my life is the best way to make my life better." Some things, like electrical repairs, medical treatment, and haircuts, are generally subcontracted out to specialists (e.g., barbers).
Personally, I cut my own hair, just because there's so little of it that it's cheaper than going to a barber, but that's kind of the point: ‘subcontracting’ is not the magic solution to all the issues [that a plant may] have to face, and mycorrhizae aren't the magic solution to making your garden work either. If you are a cactus or woolly blue curls, it's probably not worth the bother!”
Greg happened to love Frank’s subcontractor analogy above, and so do I! Frank also confirmed to Greg “that non-mycorrhizal plants are kinda the new kids on the block [especially ruderals and weedy plants], yet there are plenty of plants that are important members of vegetation communities that are non-mycorrhizal, yet mutualistic (or at least non-competitive). Bert Wilson used to laugh when I'd bring up mycorrhizae as everyone was so focused on it. He would stress that the overall plant community was the key consideration, rather than worrying about what type of fungi partnered with this or that plant.”
Ok sorry–slight detour is over–time to get back on track…
Wayne continues, “We can, in more places than we do now, integrate the complex, self-sufficient, indigenous, fully-functioning (e.g., capable of self-reproduction) ecosystems into our landscaping (literally land-scraping). This is not complicated, but it does require a different mindset:
Preserving the irreplaceable soil microbiomes upon which our indigenous ecosystems depend.” This means for developers grading a piece of virgin land, instead of viewing the excavated topsoil as a liability and placing it in a landfill, it could be sold and turned into profit from which all, including our regional ecosystems, would benefit.
Restoring functioning ecosystems to at least the margins of our parks where [currently, the existing peripheral] landscaping systems require constant care but are not used for recreational purposes.
Expanding preservation, especially where hot-spot species are.
Trading building up for building out.
Restoring ecosystems to the unpaved public spaces in both public and private developments.
Even integrating true ecosystems into our own spaces by building native urban gardens!
So, as you can see, “we need not limit ecosystem restoration to land destroyed by development.” Yet, it’s also not an issue of people simply restoring their yards and then walking away!
Ecosystem restoration techniques can be used to completely convert the entire urban yard, or as Wayne says: “People can opt to have part of their yards in regular landscaping and part as restored ecosystem, or they could incorporate restoration into their native plant landscaping. The main thing is to recognize that soil conditions must be made right first if they're not already suitable–that’s the hard part (sometimes literally). The other part is attitude.”
Wayne also points out that since “we are soon to be asked to drastically reduce our water use, this means that self-sufficient native vegetation will be near the top of the list for a different approach to landscaping. Incorporating the features of restored ecosystems into our yards, parks, commercial spaces, and certainly our highways can save a huge amount of water and give us back what we have so blithely taken for granted, ever since our non-indigenous ancestors first set foot upon this continent.”
Wayne goes on to say: “We all need to adopt a new paradigm of horticultural practices before we are forced to react to a hugely expensive and scarce water supply system, as standard practices just don't fit. But what can replace them is far easier and cheaper [functionally mimicking indigenous ecosystem functions]-and all it takes is some physical labor! People need to succeed with native plants, or they will conclude that they’re too difficult to bother with. The real problems, however, are in people’s expectations for immediate gratification, lack of patience, and unwillingness to learn a few simple crucial distinctions between traditional gardening and self-sufficient restoration.”
A cool story about Woolly Blue Curls:
I think this is a good example of what Wayne is talking about regarding people’s expectations for native urban gardens. Lee Gordon states, “For most homeowners in San Diego, the key is to have a nice-looking garden. Most gardeners do this with nursery plants that come from all over the world. These plants need considerable water, and more importantly, they can tolerate being watered too much. However, there are so many different natives growing in SD that it is easy to find locally indigenous plants that look good in a garden good year-round. To succeed, however, homeowners must add water. Consider Woolly Blue Curls–there are several of these plants growing naturally at a certain location of my neighborhood, but nowhere else. If you were to plant one somewhere else in the HOA, there is no guarantee it will stay alive without help. They probably grow where they grow because there is something about the site they like. Now suppose you can grow one in your yard that is self-sufficient and needs no additional water (i.e., "being in step with nature").” Well, Lee did this, but for half the year, his plant was “crispy brown and not pretty.” So, he added water to it and not only did it stay lush and green all year, but it also “bloomed all summer”!
According to Greg, “another interesting factoid, gleaned from Ted St. John, about Woollies (i.e., the affectionate term for Woolly Blue Curls) is that they are almost completely non-mycorrhizal! So, it appears these very stress-tolerant plants are utilizing a different survival strategy. I have seen interesting coiled root structures on Leucodendron that look almost like Frankia, but no idea if woollies use a similar adaptation. I have read that because Proteas are also non-mycorrhizal, they are more vulnerable to water molds like Phytophthora. This may be a similar situation with woollies, possibly making them more vulnerable to these pathogens. Similarly, neither Proteas nor woollies(nor most other natives) tolerate rich, amended soil well. I remember when the Mimi's restaurant first opened in Oceanside – they planted something like 30 woollies on the south side of the landscape, in amended soil and on drip. They lasted about a month!”
Ok so now for the “paradigm shift” that Wayne brought up, courtesy of Wes Hudson!
Wes asks “Why promote the use of native plants if we must ignore such a basic aspect of their life cycle as dormancy? There is a feeling I get that forcing them out of their normal life cycle is like putting a wild lion in a cage, which for me just ain’t pretty, but this use of nature is promoted because [as Lee states] the key is to have a nice looking garden (i.e., a garden that conforms to the aesthetics governed by the traditional use of non-native plants). The fact that native plants directly reflect the changes of season in our area is one of the biggest benefits to me, and it is beautiful, even visually, in a way that a so-called pretty garden just can’t be, and that underlying relation to the seasons is not dependent on changing anything, it is always there, without lifting a hose. Hence, my new T-shirt logo: Dormancy Rules! which, to me, means love the whole plant. The middle ground is how to make dormancy acceptable [to the public by using the correct selections and placement of native plants], but another ideal that could be pursed is educating people on the aesthetics appropriate to this climate (I know, good luck)!
In any case, a simple fact” that both Wes and I hope to see proliferated is that native urban gardens which never need to be irrigated after they are fully established, will save more water (and bills) than the non-local ornamental ones, “and thus one could say, are a more socially responsible agenda to promote!”
PLANTING
Planting tips from Vincent Lazaneo: “Almost any soil that is bone dry will be hard to dig. Soil should be moist when dug but not wet. Water slowly to thoroughly wet the soil then let it dry several days or longer so when it is dug with a shovel the clayey soil will not stick to it and will break apart when struck. Working soil that is too wet can make it more compact.” His recommendation: when digging a hole for planting, check how well water will drain from it – fill it with water; let it drain away; fill it again; put a stick across the top of the hole and measure the distance to the surface of the water; do this again a few hours later – if water drains at the rate of ¼"/hr, that’s very good – but if it drains very slowly or nor at all, then you have created a swimming pool that will fill with water after irrigation or enough rain, drowning the roots. “Digging a bigger hole will just make a bigger swimming pool. Some clay soils may only drain at 1/10"/hr. If water stands in the hole too long, roots will be deprived of oxygen. If a planting hole does not drain well, then it’s better to plant on an elevated mound or in a raised bed so at least a portion of a plant’s root system will not be saturated. You can use native soil or [appropriate] amendment (if desired) to increase its porosity. Remember though, that water draining through porous soil will saturate the layer where it meets soil that does not drain as well.”
More planting tips from Tree-of-Life Nursery: 1) Don't dig round holes–make them square and have the sides pincushion inwards measurably–this keeps the roots from running round in circles and the plant becoming pot-bound even though it’s no longer in a pot; 2) For planting in conditions where the soil is layered (e.g., floodplains), make the planting hole 4 times the width and 4 times the depth of the root ball (otherwise, just follow the standard double the dimensions); 3) Back fill the hole with a mixture of 50% original soil, 25% sand and 25% mulch or some type of slowly decomposing organic matter–make sure this mixture is as thoroughly homogenized as you can get it; and 4) use the remaining 50% of the spoil soil to form a shallow mound creating a basin around the plant.
Greg Rubin caveats that “if you dig a planting hole several times the width and depth of the container, then be sure to position the rootball at an initial height that is at least 1/2" above the surrounding soil. It is a given that the soil will settle over time, and you don't want to end up with a drought-tolerant native in the bottom of a hole. Xeric species planted too deep is a major contributor to losses in native landscapes (native-scapes).”
Vincent adds “whenever soil is dug up very deep it’s good to water it well for a while to let the soil settle before planting. Even so, it’s a good precaution to position the rootball a little above the native grade, with the soil sloped up to the top of the rootball so it will not be below grade later if there is more settling. As an aside, I also want to add that putting a layer of sand or gravel in the bottom of a planting hole will not improve the drainage of water from the soil above it.”
Vincent also recommends that before you plant in layered soil conditions, since the plant container is filled with potting soil or other media, make sure the bottom layer of the container is saturated before water will flow out the drain hole(s). Also, due to the layered soil conditionsbelow the planting hole, there may be saturated zones which will cause problems for plant roots. “The solution is to dig up and mix together the different soil layers to create a homogeneous mix. Adding sand may help or hurt depending on the texture of the soil you are amending. If you have a very clay soil you would need to add about 80% sand by volume to substantially change the texture of the original soil. Adding just a little sand will actually increase the soil’s density which is good if you are making adobe blocks, but not so good if you want to grow plants!”
To improve clay soil conditions, Greg recommends: using “redwood mulch for chaparral/ woodland landscapes. It promotes colonization by the right micro-organisms which tends to improve soil structure over time. It usually takes longer in hardpan soils, but I often relate a story from Bert Wilson about a site in the Central Valley that used to be a wagon trail. Nothing had grown there for years, and it was such compacted clay as to be nearly impenetrable, wet or dry. Within a year after redwood mulching, you could stick a pitchfork in it! I prefer [mulching over] soil amending, as I do not typically like to add organic soil amendments to native plantings (because) nitrates, and especially phosphorus, can have an extremely negative impact on the mycology of these sites (especially arbuscular mycorrhizae).” More on mulching next!
More planting tips from Greg: Plants “seem to love having 8"-12" rocks put right on their roots.” Why? Because “the partially-exposed rocks serve as small catchments for rain facilitating infiltration and percolation through the rock-soil interface, which is also favored by roots, while protecting the surface from erosion and also reducing soil temperature.”
MULCHING
Scott Jones asks, “Do the cryptobiotic soil surfaces allow for native seeds to germinate by random-volunteer mode (i.e., the full life cycle of sprouting, growing, regenerating…)?” Wayne Tyson writes, “Physical (cultivation, digging, weed-pulling) and chemical (fertilizers, pesticides) disturbance of soils destroys the mycorrhizal net.” Both Wayne and Greg Rubin explain that, “the floor under shrub lands includes a duff layer which is highly consolidated and facilitates growth of the mycorrhizal net. In addition, rocks along the shrub lands floor are good at moisture infiltration/retention and creating the heterogeneous environment that favors native seed germination and plant (community) development. Organic mulch can be made by shredding pruned native vegetation and mixing it up with the native soils and rocks, creating lots of safe-sites for seeds.”
Chaparral mulch comes directly from trimming or grubbing actual chaparral. Thinning chaparral for fuel modification can produce a lot of bio-mass that can be shredded and used as mulch in native urban gardens. Greg explains that he has “used chipped chaparral–it’s amazing how slowly the stuff breaks down (similar to redwood) and there are rhizosphere organisms that secrete chemical compounds to slow the decomposition for organic mulches, presumably to maintain a measured rate of utilization.”
Alternatively, redwood mulch, or Gorilla Hair, can be used in native urban gardens to simulate the natural duff layer under shrub lands because it is highly consolidated. It is a byproduct of the lumber industry and has been very commonly used in the landscape industry for decades, especially in more northern locations.” Furthermore, Greg “likes the fact that it comes directly from trees without interacting” negatively with native plants, nor does it “serve as a gateway to pathogen infection because it often contains seed from the plant community, and possibly spore from the appropriate mycorrhizal fungi. It is also devoid of nitrates (like grass clippings), chemicals, trash, fertilizers, weeds, etc. It is hardcore stuffthat most weeds hate.” After this mulch has been allowed to break down naturally for a period of years, Greg has observed “cryptobiotic crust formationin many of his older installations, and never applies mulch over areas where crusts are beginning to form, as they become the mulch!”
Scott concurs, stating a “Gorilla Hair-type mulch installation can be more desirable in some circumstances, and makes more of a knitted mat that holds together very well, and is not so prone to flaming [due to its] compactedness and less airy-ness. Some soil structural advantages can be reason to use it, especially on some relatively steep soil-covering situations. It seems to have the most ground-stick(adhering to the ground). I generally apply mulch no more than about 3/4” to 1” for native-scapes.”
It should be noted, however, that for all its benefits as an effective mulch for native shrub land plantings, according to Greg, Gorilla Hair may not be good for “desert, coastal strand, or grassland plantings” which are known to benefit more from placement of decomposed granite (DG) and rocks around these plants. In addition, Scott opines that mimicking a “SoCal chaparral scrub [habitat in your garden] doesn’t require Gorilla Hair to thrive.” He believes it’s too dissimilar from the look (aesthetic), texture and structure of the natural duff in the chaparral scrub habitats that he “sees in the wilds around San Diego.” I agree with this assessment from Scott, however, I use Gorilla Hair mulch only at the time of (and around) my new plantings, as a temporary salve to protect the bare soils in my yard from erosion caused by runoff, due to the steep slopes that I have to contend with. After establishing a decent patchwork of native foundation plants(as Greg refers to them) consisting of a stratified array of hardy, robust and resilient groundcovers and sub-shrubs, I just sat back over the next few years and watched Mother Nature do her thing – the shrub canopies eventually closed on one another tightening up the interstitial spaces between them, the leaf litter eventually formed a natural duff negating the need for any further mulching and injecting beneficial nutrients back into the underling soils to energize the mycorrhizal soup critical for a healthy stratum. One of the joyful signs that this is actually happening in my yard is the proliferation of bright green mosses and lichens forming under the canopies!
So, taking all of this into account, Greg feels, and I concur, that Gorilla Hair “really is the very best organic mulch!”
Are there any other good alternatives to Gorilla Hair mulch? Greg explains that cedar mulch “seems to have a funky zing to it” and seems in better support of cedar forest ecology (e.g., white fir, black and canyon oak, incense cedar, currants/gooseberries, pine-bracted manzanita).
Cindy Hazuka asks, “Wouldn’t mulch from the Miramar Greenery pose as much a risk as untreated soil in spreading phytophthora?” Scott responds, “There is the potential, but I have yet to see it, and the usage isn’t much, though I realize it doesn’t take much of something in disease cases to make a problem happen. Just because it comes from Miramar Landfill doesn’t mean it’s a significantly potentially harmful addition to the landscape, from what I’ve seen, and of course there are other physical environmental and cultural factors important in minimizing susceptibility to diseases such as phytophthora. The landfill offers rather clean-type mulches [which may be] good to use in urban [native-scapes], without creating a problem, but of course, native mulches are ideal. I recommend using the 2” mulch. The free mulch is coarser than Gorilla Hairand contains more non-plant-material trash. If failures of landscape have occurred due to use of this mulch, potential factors” could be related to the quantity/thickness and effectiveness of distribution, in addition to other non-mulching factors such as the species used, watering practices, planting technique, planting level/profile, and competition with established root systems of large plants/trees in the soil space. The “log chips and coarse shreddings at Miramar Landfill are light-brown or nearly straw colored (when fresh) and good for walking [on pathways] although you could instead use Gorilla Hair for a flatter textural quality to walk on.”
Scott continues, “KRC Rock and Evergreen Nurseries sometimes carry forest floor mulch, a fine mulch that is practically the same [as Gorilla Hair, as well as] walk-on bark. I’ve not known any problem with the use of those mulches with appropriate application and irrigation.”
Scott explains that “the aesthetic and particle structure and composition of a mulch is a big deal” and emphasizes that people “use personal judgement, listen to the authorities, and make choices they feel good about – that should work successfully with reasonable application.”
But do you always need to use mulch? Scott makes a great point when he says, “I find it most interesting for much of the ground to be fairly visible in native-scapes, as do other people who are keen about [that] habitat style.” Personally, I would modify this statement to read “some of the ground”-rather than “much of the ground”–for two reasons: 1) if you have steep slopes in your yard, then leaving much of the ground bare could result in an erosion problem; and 2) leaving some bare ground in your native-scape is important to have for certain ground-dwelling bee species which will also aid your native plants in the pollination services they provide-more on this later!
WATERING
Most San Diego endemic plants are adapted to drought stress – they slow down their metabolic functions – but this doesn’t mean they can do without any water at all! Wayne Tyson and Greg Rubin state that “all plants, even natives, need water from somewhere! It doesn't have to be much for well-established plants with deep and widespread root systems.” If recently planted, however, Greg emphasizes to “make sure there is water where the roots are, especially the root-ball which tends to dry out faster than the surrounding soil, because nursery stock is grown in a light growing medium that is highly porous and dries out quickly from both transpiration and evaporation, well before the surrounding soil dries out. That's why infusing as much water as possible before planting (as long as the soil drains well enough to ensure no residual saturation that might drown the plant) and after planting is recommended. Float them out of the hole! Pre-watering the holes also removes air pockets from around the rootball.”
Planting in the fall, when the weather is cooler and there is a chance of rain, is optimal but not a necessity in SoCal. As an example, Greg described how he “successfully planted a large landscape (over 1.5 acres) near Sutherland Dam (between Ramona and Santa Ysabel) consisting of fairly well-draining loamy DG soils in August with 106-degree temps. First, the entire site was watered beforehand to moisten the soil, and then the plantings were flooded during installation (5+ gallons per plant over about 5 passes). Only 20 out of 1,000 plants were lost by fall!”
Greg continues, “For summer plantings, it is recommended to irrigate a couple times per week for the first 4 weeks using an interval schedule between waterings (ranging between 3-5 days) rather than irrigating on specific days of the week; increasing the watering interval to every 7-10 days during warm weather until it starts to cool. This level of hydration works well for 1- and 5-gallon plants. To mitigate transplantation shock with larger sizes, backfill with salvaged chaparral soil (if available). When planting large box trees (36"+), install a couple moisture sensors, each on opposite sides of the rootball, at 18” and 36" depths and check periodically to ensure an acceptable range as the tree gets established. Deep moisture sensors can tell you so much about what is going on with the tree, including how much water its drawing near the surface and at depth, or if its not drawing much moisture at all which can be a sign of trouble.”
In established gardens, Greg suggests the use of modern high-efficiency permanent irrigation systems (e.g., MP-Rotators) “for plants from areas of higher rainfall, such as Ceanothus thyrsiflorus griseus, [that mimic] rainfall or fog drip as much as possible – wetting and cleaning leaves, infiltrating mulch, and more or less [watering] an even area of coverage.” Such systems “really don't use any more water than a grid-style drip system, but the delivery is completely different and much more closely allied with natural” rainfall or fog. He can install this system “and pretty much forget about over-saturation, salt build-up, invisible leaks, blockages, critters, precise emitter placement, and future re-positioning.” However, a drip system is still recommended by Greg for native plants that thrive in “high fertility/organic matter such as in a marsh or riparian ecology – rushes and sedges do just fine on drip. Even bush anemone tolerates drip; it may not be a coincidence that it too grows very close to water sources in its natural state.”
Carole Brown asks, “Do [established] natives need extra water in summer, or would this kill them due to fusarium?” Wayne responds, “Depends on depth and width of root system and soil permeability.” He suggests that watering native plants growing on a cut pad is a more reliable approach than for those on compacted fill. “Compacted/structural fill is difficult to irrigate properly because the perc rate is so slow, deep irrigation is impossible, and there's always the potential for getting too much water into the fill mass which can cause slope failures. If on compacted fill, add permeable fill and avoid surface watering.”
Whether growing on a cut or a fill pad, Wayne and Greg caution that “deeply irrigating native plants in summer can be a problem because pathogens (e.g., fusarium) are stimulated by the combination of moisture and temperature, so it’s important to keep water away from the base of the mainstem/trunk to avoid disease and to avoid over-stimulating growth. Two great methods to do this are through the use of a: 1) watering ring of stiff bendable permeable plastic pipe (butnot punched holes) buried away from the trunk deeply enough to keep the near-surface 6” from getting wet by capillary movement OR; 2) soaker hose dripping into a few pieces of pipe buried about a foot deep and spaced around the drip-line. Above all, water enough to keep them alive, but not so much that you end up with a weak, leggy tree or bush.”
Greg really likes two recent approaches he heard on watering natives, one by Mike Evans and one by Dennis Mudd:
Mike Evans recommends deep watering once a month. Greg used to have a sticky valve in his “chaparral garden and on a couple occasions in the summer the valve stuck open for something like 8 hours! Rather than destroying the native-scape, the deep watering was [actually] well-assimilated and the plants looked great!” Good drainage (DG/loam soil) may have something to do with it, but the landscape never suffered. Greg cautions, however, to be on alert for ant colonization that may be encouraged by deep watering.
Anecdotally, Greg recalled that “an anomalous rain event in July 2015 dumped something like 4" in a matter of weeks, and the natural plant communities [around San Diego] seemed to love it!” Greg believes “the key here is whether there are pathogens or pests that can be activated by the deep watering, rather than some intrinsic inability of the plant community to tolerate occasional deep watering. This might make it a bit risky in concentrated urban areas closely surrounded by nasty pathogen-/pest-rich yards.”
Dennis Mudd’s irrigation approach really jives with what Greg “learned from Bert Wilson at Las Pilitas many years ago. Bert would talk about certain plants utilizing their mycorrhizal connections to shunt moisture from wetter areas (like riparian zones) up slopes, sometimes hundreds of feet to the most stress-tolerant plants. In addition, many deep-rooted trees like oaks with surface ectomycorrhizae and deeper endomycorrhizaecan pull up moisture from the water table and share it with the plant community.
Greg believes that Dennis’ “use of semi-riparian plants like Deergrass, Mule Fat and Sycamores [in his landscaping] can help supply moisture to the overall fungal grid, making for a more forgiving approach. Dennis reports that that his overall native-scapeis greener than the surrounding wild areas, while he is only applying moisture in the riparian zones and it doesn't appear to cause problems for the overall plant community.”
Greg’s “only addition in both cases would be to still provide light overhead irrigation (on the level of summer thunderstorms 2-3 times per month) to dust off foliage, reduce transpiration, and help with foliar hydration. This is more for fire and appearance sake.”
Upon reading Wes Hudson’s posts, I wonder does the “Non-Irrigation” method really work? When it comes to his “ecology-based approach” to habitat restorations and native urban gardens, Wes states, “What is possible and what is not possible is irrelevant, at a very basic level, the needs are the same. Looked at from another perspective, the only thing taken away is weeds, and the only thing added is plants – that simple!” However, there is one major difference, according to Wes: “because mulching is not used in restored areas, they need to be watered for a longer period.”
Wes states that he “is amazed at how hard things get for young plants in restored areas, especially absent the mulching regimen he uses in native urban gardens. However, too much irrigation makes natives grow too fast, from which it becomes harder to wean them, and can also interfere with their going dormant in summer. Mulched gardens use much less water. In fact, the survival rate in Wes’ native urban gardens averages 90-95%. With mulching, a non-irrigation regimen is possible; however, this doesn’t mean absolutely NO irrigation whatsoever!” Just as discussed above, plants should be floated out of their holes at installation, then according to Wes, “watered weekly for the first month (preferably by hand), then twice a month for a few months after that (or more depending on time of year of installation), and [finally] never watered again after establishment.”
Under this regime, not all of Wes’ gardens “look like wildland wannabes, but they all seem to have the same needs. Most surprising is that, in what is the driest year on record, the only plants that have suffered in his gardens are the non-locals, with the un-watered locals doing just fine – and the supported fauna quite happy–do they know these gardens are more ecologically inexact than a real restoration project?”
Wes feels, and I concur, that it’s “important for native urban gardeners to see just how simple some things can be – and how good that feels!”
Here’s what Greg and Scott Jones say: “Wes Hudson speaks a lot of truth. He’s been implementing very successful native-scapes with no irrigation for many years, utilizing local native species. He has very little mortality from what I can see and they look like the real deal- he is as close to a naturalistic model as you can get, complete with appropriate plant communities, mulch, clean-lean-mean soils, etc. I believe Wayne Tyson's work also closely fits this model.”
So where do I stand on the watering debate? Let’s revisit Lee Gordon’s story about Woolly Blue Curls for a good example of a local perspective on the watering debate, in which he considers the finite supply of water. “Grass lawns in San Diego need something like 50 inches of water per year. Add sprinkler inefficiency, and this rises to 80 inches. Add overwatering, and this rises to 150 inches. Yards populated with non-local ornamental nursery plants need perhaps 60% of the irrigation demand that grass lawns need, “so by the time you factor in everything, they still consume about 100"of water per year. For comparison, suppose you are a homeowner who follows precisely Mike Evans’ recommendations for watering native plants–“you have to, because if you water too much, you could kill your Woolly Blue Curls”–which will put you at about 10" of total landscaping water use per year. Now, “if everyone in California properly watered [their native-scapes], landscape water consumption would plummet–Jerry Brown would be happy–agribusiness would be happy!”
Much as I would like to emulate the non-irrigation method espoused by Wes Hudson, I still enjoy the mix of locals and non-locals that grow in my yards, so I’m not quite ready to accept the losses that would occur by shutting off the spigot entirely, and then watching only the hardiest of native plants survive. Rather, I prefer the watering regime espoused by Wayne: “it just has to be in the right place at the right time in the right amounts.” In other words, “gardeners just need to learn how to read their plants.” So, recognizing that most native plants can withstand some drought and even drop leaves, I watch for signs of unhappiness (i.e., significant wilting or unhealthy-looking or dull leaves)–basically, I water infrequently for long periods and hope for the best!
LAWN REPLACEMENT
Jose Robins asks, “Should I spray my lawn with herbicide and let it die-then water, wait for new growth, and repeat this process until the grass is gone? Is this really the best way? Any other ideas besides digging it up?” Diane Kennedy of Finch Frolic Garden Permaculture, explains that if people are worried about herbicides poisoning wildlife and their existing vegetation to be retained, “how about killing the lawn by laying down cardboard with a few inches of much on the top? For cool-season grasses, people have had great success with sheet mulch-laying cardboard with mulch over it - in suffocating their lawns. There are several things to consider when doing this.First is the type of grass–if fescue, then this is a simple process and the grass will die off easily–if rhyzomus such as the dreaded Bermuda Grass, then it might take additional work and patience. Second is that suffocating the lawn returns the nutritional energy back into the soil, as native plants don't like fertilizer.”
Diane finds this method to work well for cool-season grasses: “Weed whip the lawn down to dirt; turn off all water and let it dry out completely (even in summer heat for several months); add sheets of newspaper topped with a light mulch such as Gorilla Hair; and cut through the sheet mulch and plant. Unfortunately, even after all this, Bermuda grass will rise from the dead! However, any weed including Bermuda that comes up through sheet mulch is far easier to pull out, and you just have to keep after it. A very thick layer of cardboard and several inches of mulch will help as well; far better than killing off the soil microbes with chemical applications, and then having the Bermuda come up from deep roots and/or seed anyway.
Most natives don't care for very thick sheet mulch, so it should be pulled back from where plants are installed. Note that planting through sheet mulch over green grass will kill natives from the high nitrogen load in the soil. Drying out the dead lawn first and then sheet mulching reduces the nitrogen load. Also watch for Argentine ants with sheet mulching by using judicious applications of food grade diatomaceous earth around the base of new plants, or Borax bait stations.”
Diane also notes that “some people question if sheet mulching is as innocuous as it is made out to be due to the possibility of subjecting the dirt to anaerobic conditions. Such anaerobic conditions would be in areas where there is a lot of water on bare soil which is extremely compacting, or where sheet mulch sits on sodden soil with no microbial activity below. However, there is a dearth of data to back this up. For very wet areas, using sheet mulch on top of layered organic matter builds and protects the soil.” She concludes “there will always be people on both sides of every idea, but sheet mulch done properly has proven itself world-wide as an excellent bandage for the soil. In the big picture, it is probably a good effective tool.”
Jose also asks, “For a warm season grass lawn (e.g., Bermuda) that spreads by runners, should it be physically removed manually or via sod cutter, followed by 2-3 rounds of herbicide application to decrease the chance of runners returning as weeds?” According to Diane, to do this “without herbicide, you just have to be patient for a lot of long-term laborious work. If you have Bermuda, then let it sit dried out for a month before covering with cardboard and mulching.”
POLLINATOR PATHWAYS
Ok so I’ve been giving more thought to this thread on the list-serve recently questioning whether or not restoring our yards into native urban gardens is really helping San Diego’s endemic plants survive and thrive? I guess my first reaction to this is, how does it hurt?? Right?? Obviously, in our suburban “sprawl” areas at the Wildland Urban Interface (WUI), seems to me the use of endemics that are habitat-appropriate to adjacent undeveloped lands of our County would do nothing more than to continue to reinforce Mother Nature’s labor of love–natural recruitment! There are many ways natural recruitment occurs, and one is through pollination/pollinator services. In our more urbanized areas, I see lots of big advantages for native urban gardens to contribute significantly to the recovery of San Diego’s endemic plants, especially in terms of enhancing such pollination/pollinator services! Pollinators are critical to our food supply and the diversity we find in nature, yet across the nation, they are disappearing. It is widely acknowledged that native butterflies and other pollinators are under threat from habitat loss, water pollution, the ‘cides’ (i.e., pesticide/insecticide/rodenticide/herbicide/fungicide/miticide misuse), Genetically-Modified Organisms (GMO), energy policies (Ethanol Mandate), and Climate Change.
Let’s look at the Monarch butterfly as an example. The Monarch migration is truly one of the world's greatest natural wonders, yet the population is threatened in both Mexico (due to deforestation) and North America (due to all the reasons listed above) throughout their spring and summer breeding ranges. For example, the overwintering population in California has been declining for more than a decade, with the winter of 2009-10 the lowest on record! To make matters worse, the tropical milkweed/OE Parasite is another threat which has always been there but growing exponentially in recent years.
Tropical milkweed is a non-native milkweed that has exploded in popularity in response to the demand for milkweed; is simple to propagate, allowing growers to rapidly produce the plant for quick sale; and is attractive, both to humans and monarchs, providing flowers and lush green foliage throughout the growing season. The problem is a protozoan parasite of Monarchs (Ophryocystis elektroscirrhaor OE for short) that grows on tropical milkweed, travels with Monarchs visiting the plants, gets deposited on leaves eaten by caterpillars that ingest the OE which has been linked to reductions in butterfly body mass, lifespan, mating success, flight ability, and migration success.
What can we do to prevent the extinction of the Monarch Butterfly? Firstly, the good news is that CNPSSD is a Partner in the San Diego Pollinator Alliance (SDPA) aims to increase native pollinator habitat and awareness about pollinator-friendly practices throughout San Diego County through outreach, education, and on-the-ground programs. One of our highest profile activities includes the Pollinator Pathway Exhibit at San Diego County Fair to provide hands-on learning experiences about how people can assist Monarchs and other pollinators by taking simple conservation-related actions. Many CNPSSD members have volunteered at this exhibit over the past 5 years!
An important SDPA function includes the development of demonstration pollinator gardens across the County in partnership with other agencies, organizations, businesses, and homeowners to inspire an increase in pollinator habitat creation using native plants at residences, schools, community spaces, and other public/private lands. Emphasis is on providing egg laying, shelter, and feeding habitat for Monarchs. The U.S. Fish and Wildlife Service (USFWS) Partners for Fish and Wildlife Program provides funding for initial installation of a pollinator garden including plants, labor, and signage. This program depends significantly on volunteer assistance, such as that from CNPSSD members, and the garden owners are expected to execute an Agreement with SDPA to:
Display interpretive signage created through the program
Collaborate on an onsite public workshop
Register their garden as a Monarch Waystation with Monarch Watch
Maintain the garden on a long-term basis
Submit annual reports on how the habitat is being used and if any assistance is needed
There is work to be done to conserve the Monarch population in southern California and there is a demand for conservation efforts from the public. The SDPA addresses both local- and larger-scale regional conservation needs of the Monarch and other important butterfly and pollinator species. One scale for conservation actions is very local – planting small pollinator gardens that incorporate native species of milkweed – where homeowners, students, and teachers are able to provide Monarch habitat. Pollinator gardens in public spaces act as demonstration gardens – where people can learn about the Monarch and other pollinators, and about the milkweed and other native plants – where they can take lessons demonstrated in the garden and put them into practice at home, such as the use of less harmful pest control, water saving techniques, and the value of a diverse ecosystem to pollinators. Specifically, people will want to know how they can get milkweed to be a part of their gardens!
At the same time these local actions (pollinator gardens) are happening at a small scale, the restoration community, cities, counties, states, and Federal agencies are contributing to Monarch conservation at a larger scale – through public parks, restoration projects and other open space areas. To address this issue at a regional level, SDPA is coordinating with the Xerces Society to identify parameters that should be taken into consideration when using milkweed in restoration projects, including which species are suitable for certain areas, where to source populations for seed collection, which nurseries are able to grow different species, and which seed companies can bulk-produce milkweed seeds from different species. To accomplish this, SDPA plans to build a network connecting people seeking seeds/plants to those with seeds/plants, and to identify gaps in knowledge and plant availability which will help target future funding requests. Because a network like this could benefit other pollinator species in addition to the Monarch, information about other butterfly-host plant relationships will be included into this network.
So, as you can see, small-scale pollinator gardens (native urban gardens) provide habitat for butterflies and pollinators locally to form a patchwork of habitats to benefit pollinators regionally (i.e., Pollinator Pathways). Having many of these gardens can make a difference for conservation at a larger scale!
By the way, I haven’t even touched upon the concept that creating a network of native urban gardens could also serve to ameliorate the potential for negative plant and wildlife migration effects, and possibly extinction events, due to Climate Change – the operative term here is “refugia” – I’ll leave this subject to Frank Landis to explain!
CONCLUDING REMARKS
In my journey, I’ve learned an immense amount of great info from experts like Greg Rubin who emphasizes that “what California native plants simply want is clean water, soil, and mulch without pathogens – no steer excrement, [no chipped wood (which promotes mold),] no nasty alkaline salts and minerals in the water – they just want a clean environment.” San Diego’s “intricate, delicate, complex, inter-dependent shrub land communities have little ability to defend against exotic plants and diseases, which are the worst Bulls-in-a-China-Shop one could imagine.”
Further, I very much appreciate learning about this stuff from the list-serve’s open forum of conversations, education, and sharing. I especially want to extend my appreciation to Greg for his philosophy of sharing “what has worked for the last 25 years and well over 700 installations [and not worrying about] giving away proprietary information or competitive advantage which could put him out of business,” but rather to “help build the market for all of us to participate in, welcome challenges to positions, and hear other experiences, as they often can open our eyes to other possibilities.”
I look forward to continuing my own journey, while snatching tidbits from my listserv heroes– Wayne and Greg and Frank and Lee and Wes and Vincent and Scott and Diane and many others whose knowledge I respect. In our collective march forward, and once again echoing Greg’s Agenda, it’s good “to share with folks, in an open manner, success stories with native-scapes in order to foster better experiences and increased acceptance of these materials as legitimate landscape alternatives” as long as we “continue to hear the thundering chorus of negativity about the use of native plants [not referring to CNPS, of course] and their willful exclusion in landscape design, while available habitat and regional identity disappear!”
I also share Scott Jones’ Agenda of “passionately making happen what wasn’t being done, but should be, in as many San Diego landscapes” as possible: the implementation and appreciation of native-scapes comprising “many different styles, recognizing there’s not one best way of accomplishing this work–rather, it’s a matter of circumstantial desirability. It’s both science and art!”
Just today, I saw another post from Scott that truly defines the current and ongoing status of my own journey, and most likely what it will continue to be 20+ years from now: “There’s a sort of 'in-control chaos' which all the plants thrive in. This is not necessarily a recommendation, it’s an example of what can work, among other ways that also work.”
What do these posts mean to me? Well, my yard is not a purist native urban garden by any stretch of the imagination! There is a lot of non-native stuff growing there, some I planted myself and some that just showed up–and this brings me to one last point I’d like to make about my yard–embrace natural recruitment–well, to a certain extent at least. For the most part, I pretty much allow to thrive in my yard whatever Mother Nature decides to drop off–by wind, by runoff, by bird poop, whatever – but with some exceptions. When a couple weeks ago I noticed a Brazilian pepper baby popping up, it was immediately cast off – man, I’ve seen those things really take over and dominate an area!
Finally, since I began this treatise with a quote from Wayne Tyson, gosh-darn-it if I’m not gonna finish up with him: “The sooner we learn to get into step with Nature, the better, and the easier it will be to transition to transforming our gardens into extensions of the ecosystem at large rather than being objects of our biases, aesthetic and otherwise.”
Ok, so please join me in raising your hand if you would like to see Wayne teach a university extension course! 😊
[1] And, they are native plants in dire need of protection and preservation that once were common forest-floor elements of the chaparral understory.
Banner photo: Judie Lincer’s Garden, photo by Jeff Lincer