Native Seed Starting and Germination Guide
How to Start Native Seeds
Many native seeds have built-in dormancy process that prevent them from germinating before frost or drought kills them. In the wild, seeds remain dormant until suitable growing conditions are met. In cultivation, however, successful gardeners must become familiar with some simple pre-sowing seed treatment methods that unlock dormancy processes and stimulate faster, more consistent seed starting.
Seeds should be stored in a closed (airtight) container under refrigeration (33-40°F) in a cool, dry place until ready for sowing or until pre-sowing treatments are applied. Avoid rapid or frequent temperature changes and protect yourself from rodents.
Cold, Moist Stratification
One of the most common ways to break dormancy in native seeds, especially wildflowers, is cold, moist stratification. This is the process of mimicking the changing seasons and associated weather and climate conditions naturally or artificially.
To stratify the native seeds naturally, plant them outdoors in late fall in a weed-free area and allow the seeds to overwinter.
To stratify the seeds artificially, place the seeds and medium in labeled and sealed plastic bags. and store in the refrigerator (33-40°F). Layering media can be damp paper towels, coffee filters, sand, vermiculite, or other gardening media.
Seeds requiring cold, moist stratification will typically start to germinate within 30 days unless noted otherwise. If seeds sprout earlier, make sure that you plant immediately.
Light Exposure Germination
Some native seeds like Cardinal Flower require light exposure to germinate. These seeds should be sown on the surface of your media and should not be covered.
If growing in an open ground bed, sow the seeds in layers on a flat surface (if desired). To keep the surface of the soil moist, cover it with a layer of burlap or cotton. Remove the layer after germination. Do not allow the soil to dry out until the seedlings are established. Placing window screens 12 inches off the ground to provide shade during the first season also helps prevent drying out.
If sowing in containers, water from the bottom as needed.
Warm, Moist Period Followed by Cold, Moist Period
This method of germination is common for many Spring ephemerals. Sow outdoors in spring and allow one full year for germination.
To artificially start this stratification process, mix seeds with horticultural-use medium, place mixture in a labeled, sealed, plastic bag and store in a warm place (about 80°F) for 60–90 days. Then place in your refrigerator (33–40°F) for 60–90 days before planting outdoors.
Cold, Moist Period, Followed by Warm, Moist Period, Followed by Second Cold, Moist Period
This method of germination is rare, but is observed in wild roses and Spring ephemerals like Jack-in-the-Pulpit.
To artificially start this stratification process, follow the instructions for "Warm, Moist Period Followed by Cold, Moist Period" germination for 60-90 days, then store in a warm (about 80°F) place for 60-90 days, followed by a second cold period in the refrigerator.
Cool Soil Germination
These seeds prefer to be directly sown outdoors in planting media in late fall or very early Spring.
Some species require physical breakage of the seed coat to break dormancy. Scarify by rubbing seed between two sheets of medium-grit sandpaper.
If you're directly sowing these types of seeds in-ground, there is no need to physically scarify the seed coat.
Legume species (beans, baptista, lupine, leadplant) have a beneficial bacteria called rhizobia on their roots. This bacterium can aid in the fixation of atmospheric nitrogen and improve health of surrounding plants. These rhizobia are naturally occurring in most soils and additional amendments are not needed, however, inoculate can be purchased to improve chances of germination.
Hemiparasitic species require a host plant to germinate and grow. The host plants that typically result in the most success are sedges and native grasses like Sideoats Grama, Blue Grama and Little Bluestem.
To artificially start the process, make a 2” deep cut at the base of the host plant. Sow seed in the cut, making sure seed is not more than 1/8” deep.
Even better, if a host plant is transplated at the same time as the hemiparasitic seed, you won't need to make the cut, as the hemiparasitic seed will latch on to the damaged host plant roots.
If you're looking to scatter seed directly on the landscape or garden, we recommend sowing your seed by hand in late Fall (mid-October in zones 3-5b and mid-November in zones 6-7b) or Spring.
Fall sowing gives seeds with a dormancy mechanism adequate time to germinate and naturally sprout in the Spring. Fall's cooler temperatures and generally higher precipitation encourage more water retention in surrounding soil. Plus, winter thawing and freezing helps seeds mix more easily with the soil.
Spring sowing is hit-or-miss in our experience since it may not give your cold-hardy seeds adequate time to fully complete dormancy and emerge later in the Spring. Also, it may be tougher to control weeds and competing plants if they have already begun to establish. However, it is possible to have seeds be dormant your first year of seeding and emerge the following year, outcompeting pesky weeds.
For both time periods, sow the seeds evenly in the garden with a broadcaster or add inert material like sand to make sure you're evenly broadcasting seeds and preventing clumping.
Some methods of preparing a garden for native seeds include:
Solarization is the process of covering soil surface with a clear, plastic barrier. You'll want to cut down any weeds or grass to the ground and soak the area to ensure death of weeds and grass. The plastic covering acts as a sort of greenhouse, magnifying the sun and trapping the heat underneath to "cook" the vegetation underneath. You should see good results after 2-3 months of covering if you start in the hottest months of the year (June-August)
Smothering includes using heavy-duty landscape fabric to cover the area you'd like to seed. You'll want to take the same steps of cutting down weeds and grass as mentioned in Solarization. Smothering will typically kill everything underneath, but it may take a full growing season covered to achieve a fully prepared site.
You can remove the top few inches of soil for smaller plantings with few weeds using gas-powered or hand-held tools. The benefit is that it takes much less time to prepare the site, however, you may experience more weeds due to the built up seed bank below the turf grass.
Herbicide generally isn't recommended in native plantings due to its systemic impacts to soil health and the health of ecosystems. However, selective herbicide can be used to control most broad-leafed weeds if used over an entire growing season. Using just once generally won't eliminate all weeds due to their differing emergence times.
Burning is a more advanced site preparation tactic, but a controlled burn of the site in your garden can be a lasting and effective way of controlling competing weeds.
Going over your seeding area with a rototiller is probably the best solution for larger areas where other methods may economically not make sense. This method requires multiple passes in a growing season to deal with seeds brought to the surface in the prior pass. You may need to complete the shallow tilling for 2 full growing seasons for optimal results.
Regular watering helps establish seedlings for Spring sowing, but make sure that seeds aren't sitting in water. Soil needs to be moist during the first 3-6 weeks for optimal germination. Fall-planted seeds do not need supplemental watering. If the seeds don't germinate the first year, don't give up. Germination can occur after the second year.
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