Field Pea (Austrian Winter Pea)

Austrian winter peas take about 10 degrees briefly, but sustained temperatures below 20 degrees kill them; seed suppliers rate the type as overwintering reliably only in zone 6 and warmer. In colder ground, treat the fall stand as a winterkilled cover - leave the dead vines in place as surface mulch and plant into them in spring. If you want live spring regrowth in a marginal zone, sow with a winter grain nurse crop and pick a winter-hardy variety such as Granger or Melrose rather than generic seed. Winterkill is not a failure here - a crop that dies at the right time terminates itself for free and leaves an easy, nitrogen-rich residue. The mistake is counting on spring regrowth that your winter lows were never going to allow.

Sow spring field peas as soon as the soil has thawed and can be worked, about one inch deep in soil with a pH between 6 and 7.5. Do not wait for settled weather - young plants take light frost and grow at any temperature above 40 degrees. See the inoculation rule before the seed goes in the ground. Peas do their best work between 55 and 65 degrees and stop flowering and podding above 85, so the crop is racing summer from the day it emerges. Powdery mildew also runs in hot dry weather, which is what a late-sown stand grows straight into.

Treat seed with a pea-type inoculant carrying Rhizobium leguminosarum biovar viciae at every sowing. It matters most the first time peas go into a field; where peas have been in the rotation a few times the need is less critical. Inoculant is a living culture - keep it out of heat and sunlight and use it fresh, per the label. Do not fertilize a well-nodulated crop with nitrogen. The one exception extension allows is a small starter of roughly 15 to 30 pounds per acre where a soil test shows available nitrate-N is very low or nodulation has failed. Set phosphorus by soil test rather than skipping it - adequate P is the primary fertility concern for this crop. Rhizobium partnerships are species-specific, so the strains already in your soil probably will not nodulate a pea; without the right one the crop mines soil nitrogen instead of fixing it. Free nitrogen tells the plant to stop feeding its nodules and reduces the potential of N fixation, which is the whole reason the crop is in the ground - a fall-sown stand can otherwise return 90 to 150 pounds of nitrogen per acre.

Mow or disk the stand down at full bloom. Do not wait for pods - and do not expect a cut crop to come back, since the succulent stems do not regrow well once blooming starts. Leave the residue on the surface as mulch or turn it in shallowly ahead of the next planting. Nitrogen in the crop peaks at full bloom and then moves out of the leaves and stems into filling seed, where it leaves with the harvest instead of feeding the soil. Austrian winter peas killed at bloom return 90 to 150 pounds of nitrogen per acre, and as much as 300 in a strong fall-planted stand.

Start checking when half to three-quarters of the stand is flowering. Examine five 8-inch plant tips at each of four spots in the planting, or take ten sweeps with a 15-inch net. The treatment threshold is two to three aphids per 8-inch tip, or nine to twelve per sweep. Below that, leave them to the lady beetles, lacewings, and parasitic wasps already working the field. Flowering and early pod fill are when aphid feeding actually costs yield, and they are also when the aphids arrive in numbers - the same weeks the crop is most vulnerable and most attractive.

First cut comes about 24 days from sowing, when plants stand 8 to 12 inches. Clip the growing point plus one pair of leaves to force branching, then take the top 2 to 6 inches off the regrowth every three to four weeks. A good shoot is the top pair of small leaves with the tendrils, plus a few larger leaves and any blossoms or immature buds. Stop cutting once the shoots turn bitter. Removing the growing point breaks apical dominance and pushes the plant to throw side shoots, which is what turns one sowing into repeated cuttings; the bitterness at the end is the plant shifting from vegetative growth toward flowering and seed.

Sow winter peas in late summer to early fall, roughly six to eight weeks before your first hard freeze, drilling seed a half inch to one inch deep at about 30 to 60 pounds per acre (60 to 75 pounds drilled in a pure stand). Earlier is better than later - benefits fall off quickly once you are past the end of your late-summer window. Coat the seed with a pea inoculant just before it goes in the ground. Mix with a strong-stemmed grain like oats, barley, wheat, rye, or triticale to hold the vines up, cutting the pea rate by about a quarter. Peas need enough warm weeks to nodulate and build root mass before cold shuts growth down. A Michigan stand sown in early August, right after wheat harvest, made 1.5 tons of dry matter per acre carrying over 130 pounds of nitrogen; MSU warns the payoff drops off quickly for stands sown past the end of August, so the late sowing gives up most of that benefit.