Summer alfalfa seeding should be done in August for growth before frost Farmers planning a summer seeding of alfalfa should get the planting done in August, said Vance Owens, Extension forage specialist at South Dakota State University.
"The goal should be to gain six weeks of growth after the seedling has emerged before the first hard frost," Owens said. "That should give it enough reserve energy to survive the winter," he added.
"You don't want to plant too late. Otherwise, the plant won't have enough time to grow and develop before the first hard frost or winter coming on. We want to get some good growth on it to give it the best chance to survive," Owens said.
Summer seedings of alfalfa have some risk attached. "You're always gambling that moisture is going to be available to get the seed started," Owens said.
Some areas of the state are low on moisture, and starting alfalfa there may be difficult unless they get rain, Owens said. The risk here is that if someone plants in August but doesn't have the moisture to sprout the seeds until mid or late September, and it emerges then. "When this happens it's as though we didn't plant in August anyway, so we run into some risk of it killing over the winter."
"It's a good time to seed now in August, but always be aware there is a risk of it not surviving if we don't get the right moisture at the right time for it to grow and develop prior to winter coming on."
Alfalfa seeded into dry ground in August without any new moisture prior to freeze-up and winter, may behave as a dormant seeding. "In a sense you can count that as a dormant seeding. It will be a little 'iffy,' depending on snow and what happens between now and spring," Owens said.
Normally a "dormant" seeding is done after Nov. 1. "The seed is put into the ground where we don't want anything to happen to it until next spring. Then it's there as soon as it can start to grow."
A summer seeding is always a "clear" seeding without a cover crop. That's because of the usual moisture situation in August. "A cover crop will take more moisture, so we don't recommend it with a summer seeding," Owens said.
A cover crop is designed to compete with early spring weeds in a spring seeding. A late summer seeding is expected to have less weed pressure. If weed pressure occurs next spring, the alfalfa stand, if well established in the fall, will be fairly competitive, Owens reasons. Then producers can clip if need be to control weeds, or draw upon some of the good herbicide options.
A summer seeding, if alfalfa establishes well this fall, it can be managed like an established stand next year and can be harvested two or three times, or as one would normally harvest established alfalfa.
Producers can check on SDSU's alfalfa variety trials both on the Internet and in hard copy for a discussion of varieties. Fact sheets on establishment and harvest management are available from County Extension Offices.