A “Hindsight is 2020” Series
By Justin Daniel, CNPS-San Diego President & Field Trips Chair and Grower & Collector
For part 1 click here For part 2 click here For part 3 click here
Now that the summer heat has set in and collecting season is winding down near the coast, a packet of harvested and cleaned seeds may have made its way into a cardboard box in a drawer or been pinned to a board for easy perusal. The next steps are to plan out what to do with these seeds–the fall months aren’t far off. Late fall to early winter is an excellent time to start the seeds outdoors, concurrent with the onset of cooler temperatures and the first rains of the season.
Let’s consider first what the seeds would have done had they not been collected. For many, birds, insects, and mammals might have made a hearty meal of them. During lean times, itisn’t uncommon to come across coyotescat consisting mostly of manzanita berries. Many seeds have blown across the mesas and valleys, floated downstream and lodged in sand or mud, gotten knocked into nearby rocks or shrubs, or carried tangled in fur across open spaces, or snugly placed in a wood rat larder. Some seeds will get burnt as a wildfire flares across the land. Wherever they get caught up, they lie in wait as the temperatures heat up during the day and cool down overnight, the humidity vacillates, and the elements take turns employing entropy. As time passes, the days and nights cool and the fall rains turn into winter storms. Snow and frost cycles in the inland foothills and mountains; grass and mosses turn open areas green again over the winter nearer to the coast. At some point when all the conditions fall into alignment, the dry seeds take in enough water to send out an exploratory primary root and thus a seedling sprouts.
When germinating native plant seeds, the best way to get them to sprout is to mimic those natural conditions, usually while trying to do so in an artificial or disturbed setting. Much time and study have been put into learning to propagate native plants, but there is still a lot left to learn. One way to germinate seeds is in situ, sown directly in the area that you would like them to grow. While this works well in many cases, like with our California Poppy, other times it may seem like a waste of seed. Waiting two or three years might not work for everyone, but that’s how some species propagate naturally. A lupine seed (not all) often needs a slow thinning of the seed coat in order for water to penetrate and trigger the embryo into action. Others will languish on the ground, never breaking dormancy.
For all species, research their known requirements first as a successful technique for one species may not work with another. The Calscape website has a section on Propagation for many species. Where no information can be gathered online or found in the resources below, the data may have to be created. I highly recommend the work done by CNPSRiverside Chapter’s own Arlee Montalvo and Forest Service’s Jan L.Beyers; articles are listed at https://www.researchgate.net/profile/Jan_Beyers2 . Another great reference is Seed Propagation of Native California Plants by Dara E. Emery, 6th edition 2011.
If you’ve bought seeds from CNPS-SD, the packet will have suggested methods on getting them to germinate. Much of that info comes out the links and books here. Remember that if seeds require treatment, the germination rates and survival of seedlings is often lower than for those that require none. Also bear in mind that germination rates fall every year a seed is kept in storage, as embryos eventually die during extended dormancy. Most seed older than two or three years is usually not worth paying full price for, if it is purchased at all. Over five years, the seed may be a waste of time and resources. Short-lived seeds are usually not available for sale at all. Salicaceae (often expires in hours) and Fagaceae (weeks) are families notorious for having a limited shelf life of their seeds and acorns. As always, exceptions exist.
Choose soil appropriate for the type of plant intended to be grown. Most natives do well with a mixture of 1 part potting soil, 1 part cactus and succulent mix (or decomposed granite for inland species), and 1 part equal portions of vermiculite, coir fiber, and/or peat moss to balance out water retention with optimal drainage rate. I like to add in some native soil to inoculate the mix with mycorrhizae, moss spores and microbes. Be careful on the native soil source since this method can introduce weed seeds and pathogens you do not want. A discussion on soils and soil biota will be articles for another newsletter.
No Treatment vs. Treatment
Whether sown in a deep flat, a nursery pot, or started on a clean, damp paper towel or agar plate, the temperatures and access to water ought to be consistent, and if possible, recorded. Always label the seed sown along with important dates! Some species need specific temperature ranges or hours of light, so if you’re experiencing trouble with some that don’t need treatment, try mirroring the natural seasonal conditions of the species’ native range in the months after starting the seeds. This may require some creativity and ingenuity. Using heat lamps or greenhouse frames, strategic placement in the sun, or use of crushed ice as a means of watering, are among methods that often work. Most of the time, at least some germination will occur in a normal backyard garden setup with daily care and consistent watering cycles.
Special treatments are needed to get better (or any) results when the regular sow and watering method fails. Thick seed coats, nutlets, pods, or cones often open up when pummeled, cracked, burnt, frozen, slowly dissolved with rain and minerals, or quickly dissolved in the stomach of an animal. Others are triggered by temperature or special conditions. Those in the nursery trade have found reliable alternatives to recreating natural conditions.
Stratification
Many seeds require a dormancy period of weeks to months where they sit in set temperatures. A small handful of montane and subalpine species need a cycle of temps below freezing. A small refrigerator/freezer combo is often the easiest way to do this. Some innovative people with enough space start seeds in starter trays inside the fridge and report better germination rates by doing so. Warm and cold stratification are used on a species by species basis, though most seeds prefer temperatures around 52°F/11°C, then germinate when the temps rise above 72°F/22°C after a period of a few months.
Scarification
For pummeling and cracking, some physical friction is needed. Using a file, sandpaper, gravel in a tumbler, or tools like a vice or pliers, help quicken the ability for water to get to the embryo and cotyledon. Some trial and error will be needed to examine how much force is enough or too much. Check the location of the embryo by dissecting a seed and go slow with the first few.
Hot Water
When placed in recently boiled water (180° to 200°F/82°C to 93°C) and left to soak and cool overnight, the hot water kick starts the germination process by quickly expanding and softening the seed coat. Most Ceanothus seeds and larger seed like peas and wild cucumber have better rates using this method. This is often combined with other treatment methods, especially liquid smoke (below) and stratification.
Fire, Charate, Liquid Smoke, & Dry Heat
Each of these techniques triggers fire followers by bringing the seed to a temperature or state where germination inhibitors are neutralized. If you are using fire, the technique can vary from species to species, but it is always an interesting practice to explain to the neighbors (and hopefully not the fire department) what you are doing. Non-combustible boxes and trays lined with aluminum foil do thetrick if you don’t have a grill, fire place or fire ring. Pine needles are often plentiful, and can be used; this is one way to recycle a dried out Christmas tree. Charate is a mix of dry ash and charcoal and little bits of unburnt plant material left over from a burn. Liquid smoke (unflavored) performs an equivalent action of charate and the remainder of the liquid smoke has an added benefit of being usable in marinades and BBQ afterwards. Few species need this type of treatment and consistency is hard to replicate, so bringing seeds to a high temperature in an oven and allowing them to cool in a mix of charate may work too.
Acid Treatment & Other Chemicals
Hearkening back to coyote’s lunch at the beginning of this article, some seeds of fruits, nuts, and berries do best when processed in a short ride through strong acids, such as through an animal’s gut. There are a few commercially available acid compounds that the layman can pick up from the pool maintenance shop or general store that affect seeds this way. Timing and temperature are as important for the species as the strength of the acid, so be sure to follow every precaution before attempting any type of chemistry with strong acid. Sulfuric acid would be the most dangerous, and it comes in different concentrations as a drain cleaner. Muriatic acid/diluted hydrochloric acid is slightly less acidic, but also requires precautions. Gibberellic acid can alternatively be used as a hormone inducer for germination and is considered a solid choice, though the price per gram can be daunting. If home chemistry withcaustic chemicals isn’t for you,naturally acidic soils are formed with a deep layer of native mulch and hummus, watered in with rain water that forms carbonic acid out of the atmosphere. Species that need this type of treatment often grow out of iron rich soils that naturally oxidize and release ions, especially as other plant roots interact with soil chemistry.
Light and Darkness
Finally, some seeds are photosensitive and require light to germinate, others complete darkness. For light sensitive species, sow on the surface under a clear plastic or glass cover that allows air flow in and water vapors out. Germination is triggered when the requisite hours per day of direct sunlight are met. For darkness, top the sown growing medium with a thick layer of natural mulch or leaves to be sure the light is kept from the seeds.
Getting seeds to germinate is a process that is as rewarding as it is at times frustrating. Personally, I’ve found on occasion that some seeds only germinate after recycling the soil into a new batch the next growing season, where they come up alongside another equally desired plant. In any case, now that there are seedlings, keeping them alive is a whole other story. Keep an eye out for future articles on native plant nursery trade skills and secrets, talk with your friends at the nurseries, and especially talk to each other!
If you are able and interested, please consider joining the Propagation Committee as we use tried and true methods, as well as experimentation, with our favorite native plants. Email propagation@cnpssd.org to get on the mailing list.
Cheers!