Redbud’s Tips for Seed Propagation
Set Up for Successful Propagation
For several years, I’d been intrigued by the possibility of learning to propagate native plants, but lack of a good place to grow them always stopped me from taking action. Under the tutelage of Ames Gilbert, I learned how to construct propagation tables. Like the ones at Redbud Nursery, they’re sturdy, waterproof, and self-draining. They’re also high enough that no rain splashes on the ground can reach the little plants; this helps protect plants from soil-borne pathogens. (That protection was important to me because I wanted to propagate plants for Redbud plant sales.)
I love to automate watering tasks whenever I can. Above the prop tables, I installed overhead misters connected to a hose-end timer. If you prefer, simply use a gentle hose-end spray nozzle. Set up a watering method that works for you, so everything on the prop table gets watered daily.
Taking an inspiration from Ames and Nancy’s home propagation set-up, I installed shade cloth over the propagation table. I used bungee cords and clothes pins to fasten it around the tables, to protect seeds and seedlings from birds, as well as from hot direct sun in early months.
Other Redbud propagators have different propagation set-ups, such as in a sunny room indoors, or in a modest greenhouse assembled with plastic sheeting as side walls.
Locally native seeds need no heat; they can sprout and grow outdoors as in nature!
Start with some easy species. For me, this has included common yarrow (Achillea millefolium), Western columbine (Aquilegia formosa), blue-eyed grass (Sisyrinchium bellum), both narrow-leafed milkweed (Asclepias fasciculatum) and showy milkweed (Asclepias speciosa), hummingbird fuchsia (Epilobium canum), and several native grasses.
Harvest seeds from your own plants and those of friends, exchange seeds with other folks, or buy certain species from native seed sources, listed on Redbud’s website. (Collecting seed on public lands is illegal.) When shopping for seed online, I’ve found availability best in late summer.
Collect seeds only from straight species; seeds of cultivars won’t breed true.
Cleaning seeds is important, separating seeds from petals, tiny twigs, and other non-seed material that would otherwise decay in moist conditions, possibly endangering all your efforts. Simple kitchen equipment works fine — pie pans, white plates, rolling pin, and sieves of various sizes. Keep a magnifying glass or loop nearby, for species whose seed you can’t differentiate from chaff by eye alone. CNPS has a great post on gathering and cleaning seed, including how to clean seed from berries and from capsules.
Pre-Treat Seeds That Need It
In nature, seed coatings remain remain intact until conditions favor reproductive success. Though many species don’t need help to break that dormancy, others require an extended stratification period of cold (like winter). Some need heat or fire. To find out what specific species need, I use arguably the most popular information source on the topic, Dara Emery’s, Seed Propagation of California Native Plants (available at Amazon, Abe Books, or by order from a local bookseller). CNPS offers a free downloadable version. You can also learn from Propagation Resources listed on our website.
For cold stratification, I often place seeds on a slightly damp paper towel, fold it over on all sides, then store it in a zipper plastic bag in the veg bin of the refrigerator. The smallest seeds I place in moist vermiculite, coir, or peat moss in a bag. Label each bag with species, date, and recommended length of stratification. Nancy recommends opening up each bag occasionally. I haven’t tried this, but I’m sure going to this winter, in hopes of avoiding the occasional batch of moldy seed.
Prepare to Plant Seeds
To start seed, I was fortunate in getting some 17-inch square seed trays from a friend, who recommended lining them with squares of landscape cloth. This provides a great balance of drainage and retention of seed-starting mix. You can line the bottom of any open, waterproof container with holes on the bottom; shallow containers need less seed-starting mix. (I’ve never had much success starting in 6-paks, I suspect because they dry out much faster.)
Your seed-starting mix should be a light, sterile, moisture-retentive medium made of tiny particles, that both drains well and holds moisture. Use it to maximize success in seed germination and in seedlings establishing their first tiny roots. During these stages, the plant gets all its nutrients from the seed itself; to reduce disease and other problems, seed-starting mix should be “soilless.” So far, I’ve used:
- 1 part perlite
- 1 part vermiculite
- 1 part coconut coir (or peat moss)
I mix up a big batch in a clean wheelbarrow (first rinsed, santized with isopropyl alcohol, and sprayed with water). I moisten it and fill trays. I store any leftover in a large plastic box with good-fitting lid.
Distribute seeds onto the seed-starting mixture. If seeds are very tiny, you may want to mix with builder’s sand first. Cover seeds twice as deep as seed width — except avoid covering dust-like tiny seeds and seeds that need light to germinate.
Those 17-inch seed trays are big so I often use wooden barbeque skewers to divide them into two sections and plant two species. To minimize confusion, avoid planting two species of the same genus in the same tray!
Use at least one label for each species. (Ideally, include both botanical and common names, plus planting date and any treatment info.) I was sure those little long-leafed (lanceolate) sprouts had to be grand hounds tongue (Cynoglossum grande), until not one but two Redbud propagators corrected me. Turned out they were evening primrose (Oenothera elata), which have completely different cultural needs, adult appearance, and plant communities! And despite my best efforts to label and keep them separate, I had some confusion around seedlings of foothill penstemon and azure penstemon! One side benefit of propagation: I’m getting a bit better at recognizing what certain species look like as new plants!
Water in well but gently.
Observe, Enjoy, Learn
Monitor soil moisture daily. Seed mixture should never dry out! Be patient; each species has its own pace. First to come up for me were probably common yarrow (Achillea millefolium), like a tiny forest of ferny sprouts. Then came coyote mint (Monardella villosa), with much flatter, rounded leaves. They seemed quite spindly; their seeds are so tiny that I suspect they ran out of seed-based nutrients relatively quickly; next time, I’ll pot this species up earlier than I did.
I was surprised that the delicate crevice alumroot (Heuchera micrantha) sprouted up so nicely, with almost round little leaves.
Once plants develop their first true leaves (not the initial “leaves”), you can pot them up into individual pots. Woo hoo!
Expect failures….and do your best to learn from them. Three times I tried to hot-water and then cold stratify seeds of Western redbud (Cercis occidentalis), and they got mold every time! This winter, I’ll use very little moisture around the seeds during stratification.
I also tried canyon dudleya (Dudleya cymosa), which have microscopic seeds. Eventually, a few seemed to sprout, but even those few didn’t survive after being potted up. I can’t even say if those tiny sprouts truly were dudleya. This coming season, I may try these again but inside, to give them a bit more protection from cold. I know growing these from seed is possible, as Jeanne Wilson has been growing some. Hope springs eternal.
And that’s the whole point of seeds. They represent hope, potential, the future, and the miracle of plants in our world.