What to Plant in May in Zone 6

Pigeon pea is the one crop that only works starting now

Pigeon pea needs both a long season, often 150 days or more to first pod, and soil that has fully warmed, which is why May is its only real opening in the Zone 6 calendar rather than a window that started back in April with the other legumes. Direct sow once a thermometer pushed 2 inches down, the correct depth for any seed reading, holds 65 degrees, since seed sown into cooler ground simply sits and often rots rather than waiting patiently for warmer weather.

There's a catch beyond the season length: pigeon pea is also a short-day plant, meaning it won't flower until the days shorten below roughly 12 to 13 hours, and Zone 6's May sowing spends the entire summer growing leaves while waiting on a trigger that daylight here does not reach until deep into fall. By the time flowering finally starts, an October 15 frost is usually only weeks away, which is why a standard pigeon pea variety rarely pods at all this far north. Look specifically for a photoperiod-insensitive, extra-early line bred to flower on a fixed number of days rather than waiting on shortening light, since that is the one type with any real shot at finishing here.

Peppers, melons, and sweet potato slips want warmer soil than tomatoes do

Pepper transplants want soil at roughly the same 60-degree mark tomatoes do, though a cool-natured pepper still sulks longer than a tomato does when a bed sits right at that line, which is part of why they trail the April tomato planting by a couple weeks in practice. Cantaloupe and watermelon are different plants entirely, direct sown once a 2-inch reading clears 65 degrees, safer waiting for 70 if a cold night is still forecast. Sweet potato slips are neither seed nor transplant in the usual sense; there is no germination gate to clear, just soil warm enough at planting depth, around 65 degrees, that a rooted slip does not stall in place. Black plastic mulch laid a week ahead of transplanting is worth using on pepper beds specifically, though the gain is modest: roughly 5 degrees at a 2-inch depth and closer to 3 degrees down at 4 inches, still enough to keep a pepper transplant from stalling out for 3 weeks in cool soil. Clear plastic warms the ground more than black does, but it also lets in enough light to grow a full stand of weeds underneath, which is the tradeoff that keeps black the standard pick here.

The spring perennials and greens close out fast

May is last call for a long list of spring crops, and berries lead that list: raspberry, blackberry, and June-bearing strawberry planting windows all close this month, along with the last of the spring greens like chard and mache before summer heat pushes them to bolt. Beds harvested since March should come off cutting by May's final full week, since letting asparagus harvest run into June's earlier heat here draws the crown down faster than it would in a slower-warming zone.