Frost seeding is the practice of broadcasting seeds at a time when repeated freezing and thawing is causing the ground to heave. The idea is that the natural soil disturbance resulting from this heaving will cause the seeds to settle into the soil without the need for drilling.
Frost seeding is usually performed at the end of winter, about 30 to 45 days before the average last frost, but some native species can be seeded after the first killing frost in the fall. The seeds are broadcast in the morning while the ground is frozen. A thin dusting of snow does not interfere with frost seeding.
- Minimal effort and equipment. By timing your seeding in sync with natural freeze-thaw cycles, you can reduce your seedbed preparation workload, even eliminating the need for tillage.
- Small tweaks. Frost seeding allows you to add new species to your pasture without destroying the existing stand. Over time, you can easily move the pasture toward your desired plant composition.
- Increased productivity of land base. To maintain pasture health long-term, it is necessary to replenish the soil seed bank from time to time. While this can be done by allowing pastures to rest and go to seed periodically, frost seeding means that the pasture does not have to be taken out of production.
- Natural stratification. Stratification is the process of exposing seed to cold, damp conditions for a period of time to trigger germination when the temperatures warm. Frost seeding mimics nature’s method of stratification.
- Compaction. Driving equipment over a field or pasture that is heaving is a good way to create a compaction problem. For best results, seed early in the morning, while the soil is still frozen.
- Seed consumption. Some seed may be lost to wildlife, particularly birds.
- Poor soil contact. Seeds must have good contact with the soil to germinate. Seed that is broadcast into a pasture where a stand of vegetation already exists may not make it to ground level. In most cases, a fall herbicide application or aggressive fall grazing is used to ensure successful germination. Allowing cattle to graze the pasture after seeding will also help trample the seeds into the soil. Obviously, soil contact is not a problem if you are seeding to improve a forage stand with bare spots.
- Stand failure. Sometimes a late freeze will occur after the seedlings have germinated, causing plant death.
- Competition. Because frost seeding necessarily involves seeding into an existing stand, the new plants will face stiff competition from the established residents, in addition to any weeds that may emerge. Judicious grazing can help keep the competition in check, provided that the tender new plants are protected from overgrazing.
Frost seeding is usually used in a few specific applications:
- Establishing cover crops in winter wheat or barley.
- Improving a forage stand, as in a pasture or wildlife food plot.
- Adding new species to native prairie gardens.
- Repairing bare patches on a lawn.
Plant species that respond best to frost seeding display the following characteristics:
- Seed density.
- Seedling cold tolerance.
Thus, frost-seeded species with a high success rate include:
- Red clover.
- White clover.
- Birdsfoot trefoil (depending on variety).
- Perennial native wildflowers.
However, the characteristics of the soil also affect success. Soil type is important, as some amount of clay is necessary for heaving, making clayey and loamy soils the most suitable for frost-seeding.