Cover crops

Pick a goal or the crop you are following, then open a note for timing and caveats. Pairs with What can I grow? and companion planting when you plan successions.

Goal

Any Nitrogen fixation Biomass / organic matter Weed suppression Quick turnover (≈6–8 wk)Winter / shoulder season Pollinator support Soil structure / deep roots

After this crop

Rough rotation memory for what the last planting tended to demand — not a soil test.

Any Tomato / pepper / eggplant Brassicas Squash / cucumber / melon Corn Beans / peas Lettuce / greens Carrot / roots Onion / garlic

Buckwheat
Buckwheat (Fagopyrum esculentum)
Classic summer gap filler: sow after an early harvest, let it bloom for pollinators if you can, then mow or till in before seeds mature unless you want volunteers.
Winter rye
Cereal rye (Secale cereale)
Aggressive grower with allelopathic reputation — terminate early enough before corn or small seeds unless you plan a tilled stale seedbed.