Clovers & Alfalfa - Key Growing Information
Uses: Clovers and alfalfa are small-seeded legumes that fix nitrogen, loosen compacted soil, hold soil against erosion and feed pollinators. Inoculating seed with the matching rhizobia boosts both growth and nitrogen fixation.
Culture: Plant ¼–½" deep into a firm seedbed at the rates below, using the higher rate when broadcasting. For management purposes, these legumes fall into two groups: annuals, and perennials or biennials.
Annual:
Crimson clover – grown as a summer or winter annual depending on location. In Zone 6 and warmer, it's usually sown 6–8 weeks before the first frost, overwintered, and terminated in spring. Farther north, a spring sowing produces plenty of biomass and nitrogen by mid- to late summer. With good snow cover it sometimes survives in parts of Zone 5, so growers there should plan for spring termination.
Perennial/Biennial:
Alfalfa – best known as a forage and hay crop, but also useful as a nitrogen-fixing cover. It starts slowly, then grows fast once established. Sow in early spring or late summer, often with a small grain as a nurse crop.
Berseem clover – drill it, or raise the rate if broadcasting. Spring plantings grow quickly, producing heavy biomass and fixing roughly 100–125 lb. of nitrogen per acre. Sown in late summer in cooler areas (Zone 7 and colder), it winterkills and leaves an easy-to-incorporate mulch for spring.
Dutch white clover – drill or broadcast in early spring or fall, alone or in a mix. It frost-seeds well into overwintering covers such as winter rye or wheat, and can be broadcast into standing fall crops, establishing under the canopy and carrying on after the crop is terminated. Plant no deeper than ¼"; the seed is smaller than red clover. Most white clovers spread aggressively, so keep rates low.
Mammoth and medium red clover – sow from early spring to late summer. Both are commonly frost-seeded into winter grains or overseeded into a standing crop at last cultivation. Both tolerate mowing, though medium red bounces back better.
New Zealand white clover – a strong choice for living mulch because it tolerates mowing and foot or vehicle traffic. Sow from early spring to late summer, or frost-seed into a winter grain.
Sweet clover – grows slowly the first year, then produces impressive biomass in year two. Sow from early spring to late summer and terminate before it sets seed; it produces a lot of hard seed and can turn weedy if not managed.
Seeding Rates: Alfalfa: ½ lb. per 1,000 sq. ft. or 15–20 lb. per acre; halve this when sowing with a grain or grass.
Berseem clover: ¼–⅓ lb. per 1,000 sq. ft. or 12–15 lb. per acre; halve in a mix.
Crimson clover: ⅓–½ lb. per 1,000 sq. ft. or 12–20 lb. per acre, alone or with grain or grass; halve in a mix.
Dutch white clover: ¼ lb. per 1,000 sq. ft. or 6–8 lb. per acre; halve in a mix.
Mammoth and medium red clover: ¼–½ lb. per 1,000 sq. ft. or 8–12 lb. per acre. New Zealand white clover: ¼–½ lb. per 1,000 sq. ft. or 5–15 lb. per acre. Sweet clover: ¼–½ lb. per 1,000 sq. ft. or 8–12 lb. per acre. Halve each of these in a mix.
Light Requirements: All do best in full sun but tolerate some shade.
Soil Requirements: Clovers and alfalfa grow best in cool, well-drained soil near neutral pH. Sweet clover copes better with heavy ground and is often used to break up compaction and improve tilth.
Height: See each product description.
Harvest: Established stands can be grazed or cut for hay. Alfalfa, New Zealand white clover and medium red clover hold up best to repeated cutting or grazing.
Termination: As green manures, these legumes can be terminated at any stage, but for the most nitrogen, incorporate them at flowering. Mowing first and then tilling with a rototiller, disc harrow or plow is the usual approach. On a small scale, tarping for at least three weeks also works. Second-year sweet clover is tall and tough, which makes it harder to handle without bigger equipment.
