Many of the mail-order seedhouses offer cover crop seed in smaller amounts. The specialist in unusual cover crop seed is Albert Lea Seedhouse in Minnesota. The shipping cost, about $70 per 50-lb bag, makes it most appropriate for smaller scale trials.
Local farmers and dealers may have farm-produced medium red clover, small grain and buckwheat that is suitable. Make sure it has no weed seed and germinates well. Not sure? Contact the New York State Seed Testing Lab. 315-787-2242
In New York, the suppliers below have cover crop seed for bulk purchase. These are often the primary distributor or actual producer, which keeps the price down. The delivered cost may be lower through your local farm seed dealer.
Hall, NY with warehouses in PA and VT.
Cover crop seed not currently online. Small grain, buckwheat, annual ryegrass, Sorghum-sudangrass.
Ernst Conservation Seed
Ernst is a long-time seed producer of many kinds of cover crops, native plants and conservation species. Of particular interest are buckwheat, Bonar, Dwarf Essex and Rangi rapeseed, Appin and Pasja turnip. They have scheduled truck delivery to New York.
Lakeview Organic Grain
Penn Yan, NY
Small grain, including spelt and triticale. Buckwheat. Often trying new things. Certified organic. A Klaas and Mary-Howell Martens enterprise.
Steve Groff Seeds
717 575 6778
Steve's own selected "Tillage radish" and early maturing hairy vetch. Also distributed in NY by Leon Bird 1-800-743-2473 firstname.lastname@example.org and in PA by Lancaster Ag Products 717-687-9222
The Birkett Mills
Penn Yan, NY
Buckwheat. The biggest processor in the East also sells cover crop seed.