As a propagator, I often try different approaches to germinating seeds of certain species. Sometimes I get such a definitely positive response to one pre-treatment method, that it becomes the one I’ll always use—like soaking toyon seeds for just one hour before sowing. This treatment results in vigorous germination. I won’t bother with a hot coffee soak of these seeds again. We pot native shrub seedlings into tube-style pots that are designed with internal ridges running the length of the tube. This encourages roots to grow long and fairly straight, and helps to prevent roots from circling and eventually strangling themselves. The seedlings stay under shade for several months, and as they get potted up to larger style tubes, and eventually to tree-pots, they also get more and more exposure to direct sunlight.
Summer is a time for starting perennials and some shrubs from seed. Most often, I’m working with seeds that were collected last year, and at the same time I’m doing a lot of seed collecting. I actually start collecting some seed in late spring. Early-blooming wildflowers like phacelias go to seed by late April when the days get warmer, as does miner’s lettuce. I’ve got stands of different clarkia species to collect from, and I’ll be checking the seed development of the native salvias.
I’m always amazed at the abundance of seeds that most plants produce. It makes me think about all the different functions that seeds serve. First they are food for all sorts of insects and other invertebrates, for birds and rodents and other mammals. Seeds also ensure the survival and genetic diversity of a plant species, and some portion of seeds produced each year may lie dormant, hidden or camouflaged for many years as insurance against bad years for a particular species. I make sure to leave plenty of seeds for all the creatures, and collect in such a way that anyone following behind me would never notice a difference. When I’m collecting seed, I keep this little mantra in mind: If you see more than ten fruits on a plant, take only one in ten. If you see nine, take none.
The only seed I still collect once the rainy season has begun is from toyon (Heteromeles arbutifolia). I’m picking handfuls of bright red, mature berries and contained within each berry will be one or more seeds. The berries will be soaked in water and after a few days gently macerated, which makes it easier to separate the seed from the flesh of each berry.
By the time the rains start, I’ve finished with most of the seed collecting for the year; in many species seeds mature as the seed pods dry, and so collection is done only during dry weather. I collect only from plants with prolific seed set, and then take only small amounts of seed from a number of different plants of the same species. Collecting seeds over a number of days or weeks also increases the genetic variability.
Collected seeds are temporarily stored in open containers all over my house, until they are thoroughly dry. Then I clean and package the seed in the evenings or on rainy days, when it’s not possible to work in the garden. Using simple tools and a set of graduated sieves, the seeds are separated from their pods, capsules, follicles, siliques, or schizocarps.
In botanical terms, these are all different types of fruits, as is a berry, and fruit is the correct botanical term for any mature ovary containing seeds. Plants are grouped together into families based on similarities of flower and fruit structures. Botany for Gardeners by Brian Capon (Timber Press, 2005) is a very useful and interesting book for those of us who are learning about botany as we garden.
Plants in the evening primrose family (Onagraceae) set seeds in capsules, which are usually four-chambered. When I collect seed from clarkias, annual plants in this same family, I cut the tops of stems with capsules attached. These plants produce a prolific amount of seed, much of which is eaten by insects and birds.
Finches usually eat seeds while they’re still on the plant. I’ve watched little goldfinches moving up and down the stems of clarkias and yellow evening primrose (Oenothera elata ssp. hookeri), a biennial plant in the same family, taking seed from the open, upright capsules. Birds are messy eaters, so much seed is scattered on the ground where birds like towhees, juncos and golden-crowned sparrows forage. While they’re foraging with the typical sparrow “double-scratch” method, the seed that is not eaten is scratched into the ground, ready to germinate as soon as the rainy season starts.
Within a week after the first rain in October, dense patches of tiny seedlings are evident all over my garden. There’s some predation, since voles and sparrows like to eat greens, so the patches get thinned out a bit but still, hundreds of seedlings survive. Two months later these seedlings are well developed, about 2 to 3 inches tall, with “true” leaves fully formed, and easy to transplant.
So, although we start a lot of annual wildflowers from seed under controlled conditions in the greenhouse, we also simply transplant a lot of seedlings that I dig out of my garden. Using a hori-hori knife, I can gently tease the seedlings out of my beds and gravel pathways with root systems intact. Then I immediately place them in soil in a trug, making sure the roots are covered. That same day we transplant the seedlings into 4” pots, let them recover for a few days in the shade after transplanting, and then grow them on in a sunny, protected location.
The most important things to be aware of when working with these delicate seedlings: cover roots quickly with soil, and always handle them by their leaves, not the stems. Delicate hair roots can die within minutes when exposed to air, and if the stem is crushed or damaged the lifeline is destroyed, and the seedling will not survive.