December: Seed—dispersal, stratification, germination
As the snow begins to fall and winter finally sets in, our staff pivots from field work and focuses on indoor activities, such as putting the greenhouse to bed, servicing tools, revamping the trucks and organizing the shop. However, one of the most important cleaning and organizing tasks isn’t about vacuuming the dirt from between the truck seats or sharpening our shovels—it’s cleaning and storing seed for the winter.
The two main ways plants reproduce is through spreading by roots and shoots (asexual) and by seed production (sexual). It’s really fun to step back and think about the creative and simply amazing ways that seeds move around in our environment.
We’re all familiar with the wind-dispersed dandelion seed. Well, native milkweed species spread the same way, throwing out their parachute-like fibers with their round, brown seed attached. Other seeds may rely on being carried by animals, like burrs sticking to fur (or maintenance crew members’ pants), or Jack-in-the-Pulpit seeds being eaten by birds and deposited elsewhere in the forest. Some plants like White Trillium also provide a tasty treat (called elaiosomes) for insects like ants or wasps that carry the seed back to their underground nests where they germinate.
Plants such as wild lupine and wild geranium have an even more interesting method: their pods explode with enough force to fling seed through the air! The seed pods grow in such a way that they build tension, and as the pods dry out, they reach a breaking point and the dramatic popping throws the seed away from the parent plant. Jewelweed is sometimes called the “touch-me-not” because it uses the same explosive, spring-loaded dispersal, with mature pods breaking open when touched by humans, animals, or even a raindrop.
Seed production varies by plant species, and thus, the seed ripens at different times throughout the growing season. We are out collecting even as early as May when spring ephemerals like Virginia bluebells go to seed. And fall is the prime time for collecting the late bloomers, like our native asters. Seed collected by our crews is brought back to our office and is stored in our special seed room. Here, most of the seed is spread out to dry. In the winter, our team spends the chilly days cleaning, sifting, sorting, processing, and organizing our seed stock.
Of course, our state native plant seed stock is tough, just like hearty Minnesotans. Native seed is adapted to endure long winters and freeze-thaw cycles before finally germinating in the spring. After the seed is cleaned in the office, most species require periods of cold and/or wet conditions before they can grow, so they are stored in the refrigerator under damp conditions. This process is called “cold stratification, which sort of mimics cold winter conditions out in the field.
Some seed species also require scarification before sprouting—which just means scratching up the tough outer coating of the seed. This allows moisture and light to penetrate the seed coat, letting it know it’s time to shed the jacket, send out roots, and enjoy the burgeoning spring.
After each seed species gets the specific treatment it needs for springtime success, it graduates onto the germination greenhouse. In February, we kickstart the new year by firing up this greenhouse. Keeping detailed germination history records helps us to determine exactly how to efficiently germinate each species. Certain species can be trickier than others. Then in March, seedlings are transferred into our larger production greenhouse where they are transplanted into larger containers.
We are very proud to offer an incredible variety of native plant species in which seed is collected locally. Our propagation is totally organic and pollinator friendly. We grow all of our plant material for our restoration projects, and offer these same high quality plants in our retail greenhouse. We offer special wholesale prices for larger orders. Feel free to call us this winter to talk plants and place an order that will be ready to go in the spring.
We look forward to talking with you and seeing you at the greenhouse this spring!