The cold and often dreary days of winter don’t seem like prime time for planting, but Forest Preserve District crews are hard at work this month preparing and spreading native plant seed as part of their annual snow seeding work.
Seeding and planting are typically thought to be springtime projects, but winter is actually a good time to seed. Many of the native plant species we want growing in our wetland and prairie habitats require a period of cold, moist weather to successfully take root.
This period of stratification is required for the seed to germinate come spring, said Juli Mason, restoration program coordinator for the Forest Preserve District. Some seeds require 30 days of this cold, moist weather, while others may need 60 days or 90 days. That’s why now is a crucial time of year.
“The earlier in the winter we can get it (spread), the better we can hit all those periods,” Mason said, adding that they try to get all seed spread by March 1.
Before snow seeding can happen, the seed has to be prepped for planting. That work actually starts in the spring and summer, when seed is collected from various native plants that will be included in the winter seeding efforts. That seed is then dried and cleaned, separating the seed from other parts of the plant using a machine called a hammermill, said Allison Borecky, a natural resources management crew leader for the Forest Preserve District.
The collected seed is supplemented with purchased seed, and then different seed mixes are created using formulas determined by Mason. The first consideration in determining these formulas is where the seed will be going.
All seeds have specialized habitats where they are best suited for planting, Mason said. There’s a suite of plant species that grow in wetland habitats, for example, and a separate suite of species for dry prairie. She also considers light conditions for the area and how much sun or shade a particular species of plant needs.
The volume of seed required for snow seeding is determined based on seeds per square foot ratios and the number of seeds per ounce for a particular plant. Availability of seed also plays a role in the formulations, Mason said. Some plants have seed that is easy to collect. In addition, some years are boom years for seed production in certain species, while other years may be down years.
Once the seed is prepared and mixed into its appropriate formulations, it is ready to be spread in the preserves. This year, the District will be using a new seed spreader to make the work more efficient. The new machine is a pendulum seed spreader that can be calibrated, allowing the rate that the seed is distributed to be adjusted. This means seed can be distributed more evenly, Mason said.
The priority for snow seeding each season is newly restored areas and land that is being restored after its previous use as agricultural fields, Mason said. This is particularly important because these are now bare fields that need seed so the appropriate plants grow in, rather then letting weeds and invasive species to take over.
“Whenever you kill or remove something, something new is going to grow in its place,” Borecky said. “We’re trying to make that something new a good thing.”
In addition to newly restored land, winter seeding is also done each year in existing natural areas that need enrichment. This is called overseeding. These might be areas where herbicide applications were used to control invasive species or where brush removal was done.
“They just need a little boost,” Borecky said.
Each year, the District seeds between 50 acres and 100 acres of newly restored land, Mason said. The amount of land that is overseeded varies from year to year, but is usually between 20 acres and 50 acres.
Winter seeding will continue for much of the remainder of the season. Ideally, the best time for snow seeding is just after it begins to snow, Borecky said. This allows snow to cover the freshly spread seed, protecting and insulating it until weather conditions are right for it to germinate.
“We want it on the ground before it thaws (for spring),” Borecky said, adding that the frozen ground is ideal both for the equipment they use as well as the seed.
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