When to Plant Peas

Peas do not need warm soil, they need ground they can come up in. The published floors disagree: Oregon State's germination table and Washington State's growing guide give 40°F, Illinois Extension plants into soil at 45°F or higher, and Seed Savers Exchange and the University of Connecticut both say 50°F. The disagreement is about the bet rather than the plant. Oregon State's own table times emergence at 36 days at 41°F, 13 days at 50°F and nine days at 59°F, so one sowing is a five-week wait in one garden and a week and a half in another, and a pea sitting in cold wet ground for five weeks is a pea a soil fungus can reach first.

That is why the check worth running is workability rather than a number. Illinois Extension's test is ground dry enough to till and not sticking to garden tools, and Washington State pairs that same condition with its 40°F figure. Take the reading at sowing depth in the morning, after the bed has had all night to shed the day's heat. A raised bed against a south wall reading 45°F at dawn is an honest reading of ground that will warm quickly; the same bed at noon is reading the sun, and it says nothing about the week the seed spends in it.

Peas are called frost hardy, and the label is right about the wrong stage. Washington State's guide gives a seedling's tolerance as 28°F and puts damage to the top growth below 21°F. Clemson's factsheet supplies the other half of the sentence: garden peas withstand frosts and light freezes, although the blossoms cannot. Cornell Cooperative Extension's fall guide turns that split into numbers, with peas surviving frosts at 28°F to 32°F.

As a schedule, that means a freeze after sowing costs growth, and the same freeze a month later costs the crop. Minnesota Extension's instruction for the flowering stage is to watch for a late spring frost and cover the plants with sheets or row covers, which is protection worth fitting to a flowering row and not to seedlings. By the time the cover is doing something, the pods are what it is protecting.

Clemson's garden-peas factsheet is the clearest example of how the fall question gets answered at cross purposes. It prints planting dates for both of the state's regions and gives the Piedmont a fall window running from mid-August to the end of October. A few lines above, it says that fall plantings are not recommended. Both statements are about one crop in one state, and neither is a mistake: the table answers when seed can go into the ground, and the sentence answers whether the crop is a good bet in a summer that stays hot and humid into September.

Cornell Cooperative Extension publishes the method that settles that question for any garden. Count the days to maturity, add the days the seed needs to emerge, and count the total back from the first killing frost, which its own region places at 28°F. Run that sum over the published pea intervals and they stop contradicting one another. Six to eight weeks before a fall frost is the interval The Old Farmer's Almanac publishes, and it is a short-season variety counted without the days it spends emerging. Eight to ten weeks is that figure with the seed's own days in it, which is why Connecticut's factsheet gives that interval. Cornell's own table puts peas at nine and ten weeks before its killing frost, which is that arithmetic run from the other direction.

The other end of a fall sowing is the ground it goes into. Oregon State's table gives pea a maximum germination temperature of 85°F, and a bed cleared in August sits above that in much of the country, so the seed waits out the rest of the summer before it starts. Washington State's rule for the fall crop is the whole budget in a line: temperatures should stay above freezing for two or more months after planting. Where the ground cools late and the first hard frost lands less than three months after it, the arithmetic does not work, and keeping the bed for a spring sowing is the better answer.

The three edible kinds are one crop at three harvest stages, and every soil reading and frost rule here applies to all of them. Clemson's grouping is the clearest: English or garden peas are shelled and only the seed is eaten, snap peas are eaten whole with full-sized peas inside a thick pod, and snow or sugar peas are eaten whole while the pod is still flat and the seeds are barely formed. Wrinkled-seeded varieties are sweeter than smooth-seeded ones and are the ones usually chosen for a home garden.

What changes between them is days rather than dates, and the spread is wider than most gardeners expect. Illinois Extension's variety list runs from 52 days to 72 days from sowing to harvest, with its edible-podded selections in the middle at about 58 to 61 days. For a late sowing the shortest-season type matters more than the window, because the weeks in front of it are already tight. Connecticut's factsheet adds one more fall consideration: powdery mildew resistant varieties are the ones to sow when the crop will finish in damp weather.

Southern peas, cowpeas, black-eyed peas and crowder peas are not garden peas, and Illinois Extension files them with the beans: a warm-season vegetable grown the way beans are grown. Clemson's southern-pea factsheet puts a number on the difference, with germination and emergence at their best only once the soil reaches 60°F, against the 40°F a garden pea will start in. Advice for garden peas read onto them inverts the season, and the sowing that suits one is a month early or a month late for the other.

Ornamental sweet peas are the more serious confusion. They are Lathyrus odoratus rather than Pisum sativum, and Washington State's pea guide is direct about them: the flowering varieties and the rest of the genus are not safe to eat, and no part of them should be harvested as food or fed to animals. A trellis of sweet peas along the same fence is a fine thing to grow, and the pods on it are not a crop.