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Forage Brassica Planting Calendar

Forage brassicas grow quickly in cool weather, so the calendar is built around when you want to graze and how many growing weeks you can count on.

When should you plant forage brassicas?

Extension publications from Michigan State, Wisconsin, Mississippi and Kansas State describe two common windows: late summer seeding for fall grazing, and in some regions early spring seeding. Brassicas do well in cool, moist weather and can be seeded after a cereal grain harvest or a failed crop.

The method is to start with the date you want to begin grazing, subtract the weeks your chosen type needs from seeding to grazing, and check that the result falls before your hard freezes. Extension guides list the weeks for each type; confirm them for your area.

Different brassica types, such as turnips, rape, kale and radishes, mature at different speeds and tolerate cold differently, so the right window depends on the type you buy. Seeding in a second pass or on a staggered schedule can also spread your grazing across several weeks instead of ending all at once.

How do you work backward from frost?

Look up your average first fall frost date. Turnips and other brassicas tolerate light frost and often keep quality into the cold season, but they need enough growth before conditions turn.

For example, if your first frost normally arrives in late October and your selected type needs about two months to reach grazing size according to your state guide, you would aim to seed by late August. This is an illustration only; use your local numbers.

Remember that frost dates are averages. A mild fall stretches your window while an early freeze shortens it, so build in a safety margin of a week or two when you can.

What seedbed and moisture do brassicas need?

Brassica seed is small and needs shallow placement and good soil contact. Firm seedbeds, whether prepared or no-till, give better stands than loose, fluffy ground.

Moisture at seeding is the main risk in late summer. If soil is dry and no rain is forecast, delaying a few days is often better than seeding into dust.

Weed competition can sink a small-seeded crop, so a clean seedbed matters. Ask extension about weed control options that fit your field, and read any label restrictions before applying anything. Drought is the usual reason brassica stands fail in late summer. If your area is dry, ask extension whether a later seeding or a different species fits better.

• Seed shallow into firm soil
• Check soil moisture before seeding
• Match seeding date to your first fall frost
• Use a soil test to decide on lime and fertilizer

Can you mix brassicas with oats or other crops?

Kansas State and other extension sources describe mixes of oats and turnips to extend the grazing season. Mixes can spread risk and add forage variety, but each species has its own best seeding window.

Pick a mix that suits the shortest-season partner and your frost date. Ask extension for local trial results before committing a large acreage.

If you plan to graze in strips, think about fencing and water access before you seed, since those decisions affect how much of the stand you actually use.

What grazing and animal health precautions apply?

Brassicas can cause health problems if animals are moved onto them abruptly or fed only brassicas. Extension publications recommend a gradual transition and supplementing with dry forage.

Because this is a livestock health matter, talk with your veterinarian and extension specialist. Also check the label for any grazing restrictions on herbicides used on the field or on the previous crop.

Also check the label rules on previous herbicide use, because some products leave plant-back restrictions that can harm a brassica seeding.

What should you check afterward?

Note the seeding date, rainfall afterward, the date you began grazing and how many grazing days you got. Compare with the previous year.

If stands fail repeatedly, look at moisture, seedbed firmness, seed depth and weed competition before changing the date.

Record soil test results alongside planting notes. Brassicas respond to fertility and soil acidity, and a field that struggled may simply have needed lime. Note also how animals responded to the forage and how you transitioned them. Those notes help you set up the same program with fewer surprises next year.

Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.

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