Volunteer Powered Seed Sowing
New England Wild Flower Society propagates many species of plants from seed. Kate Pawling describes mid-December seed-sowing.
By Kate Pawling
Mid-December is seed sowing time at Nasami Farm and our most recent effort was powered by dedicated volunteers. During the growing season we do sow some species as they are collected and cleaned, most notably many woodlanders, like Sanguinaria canadensis (blood-root) and Hydrastis canadensis (goldenseal). These spring ephemeral seeds often have multiple dormancies and do not store well. For instance, Caulophyllum thalictriodes (blue cohosh) doesn’t emerge until the second or third spring after it is sown. Other seed, like Viburnum dentatum (smooth arrowwood), can be stored dry, but requires months of moist, warm conditions, followed by cold to germinate. However, the bulk of the seed that we collect gets cleaned and processed, then stored in the Litowitz Foundation seed room until December.
Nursery staff spends much of late fall and early winter indoors in front of computers, planning for the next season. But for a week during December, we work with groups of volunteers who arrive in the morning and spend the day in the greenhouse sowing seed. First we prepare seed flats, filling them with sifted germination mix, tamping the mix down, and watering thoroughly. We make flats a day ahead, so they have plenty of time to drain. We measure out the amount of seed to sow, make labels for the flats and code each seed according to its germination requirements.
The volunteers then take those seeds and treat them accordingly. Tiarella cordifolia (foam-flower) needs light to germinate, so the seed has to be surface sown. Baptisia tinctoria (yellow wild indigo) has an impenetrable seed coat, so they scarify the seed using sandpaper. Sarracenia purpurea (purple pitcherplant) has a waxy coating on the seed, so we soak it in water with dish detergent to break down the coating. And so on. We keep hand lenses nearby so volunteers can take a closer look at the seed they are working with, which is a favorite activity of many volunteers. Each seed we sow is different. Viewed under magnification, the variation in seed morphology, even between species from the same genus, is breathtaking.
Seed sowing has a number of similarities with cooking by recipe; the volunteers and staff often compare it to baking. After a seed is sown into a flat, it has to be covered with the right amount of soil. The rule of thumb is to cover the seed as deep as it is long. We use a wide-screened sieve for topping the seed with soil because it gives us the most control. You can’t help feeling like you are topping a cake with powdered sugar when you tap the sieve over the seed flat to sprinkle just the right amount of soil on top. Finally, we cover all of our seed flats with a 1/8” layer of course-grit filter sand and water them. In the end we are left with a bunch of in-edible layer cakes which, with luck, will germinate in the spring. Of course, rather than putting these cakes in the oven, we give them a nice, long winter freeze.