Summer is nearing its end and it is time to plant cover crops.

Extension agronomist Sjoerd Duiker says many cover crops need to be planted early to derive the substantial benefits. Radishes have to be planted in August to develop a root system that can increase porosity and draw nitrates from deep in the soil, bringing them to the topsoil for use by next year's corn, oats, sorghum or sudangrass crop.

Oats should be planted now as well to put on substantial growth that can be grazed or harvested this fall prior to winter kill.

Crimson clover and hairy vetch need to be planted in August or early September to develop enough growth to come through the winter and fix atmospheric nitrogen for next year.

Annual ryegrass should be planted before mid-September to come to the winter successfully.

Winter-hardy small grain cover crops — rye, triticale, and wheat — are planted later, but it is important to have the seed on the farm to enable planting right after harvest. For wheat, it is important to respect the Hessian fly-free date, which ranges from early September to early October in Pennsylvania. Learn more at and consider getting resistant varieties.

Beyond Hessian fly, for small grains including wheat, be mindful of aphids and the risk of planting too early. Aphid colonization can transmit disease, like barley yellow dwarf virus, to the cover crop, which can be then move to small grains being raised for grain.