What to Plant in May in Zone 4

Your last frost clears early enough to plant with real confidence

With an average last frost around May 10, the first half of this month is usually safe for tomatoes and squash here in a way it simply is not one zone colder, where the same crops wait 2 more weeks. Confirm with a soil check anyway: 60 degrees at 2 inches deep, held for 3 consecutive days, is the number that matters more than any date. Pepper wants that same 60-degree mark, just measured 4 to 6 inches down since it goes in as a transplant rather than direct-sown seed, and it sulks longer than tomato does if that reading is only just met.

This earlier clearance is also why succession sowing works differently here. A second round of bush beans sown midway through the month, right behind the first, has time to mature and get harvested before midsummer heat stresses flowering, a gap that a shorter season one zone north often does not leave open.

New Zealand spinach and amaranth leaf need real heat, not just frost-free soil

Both of these greens are new to the table this month and both stall badly in cool soil, unlike regular spinach which prefers it. Wait until soil has held above 65 degrees for a few days before sowing either, even if that means planting them 2 or 3 weeks after other crops go in.

Space New Zealand spinach generously, about 18 inches between plants, since a single plant sprawls to fill 2 feet of row by midsummer and will smother anything planted too close.

Amaranth leaf germinates fastest when scattered on the soil surface and barely covered, no more than an eighth of an inch, since the tiny seed struggles to push up through anything deeper. Keep the bed misted rather than heavily watered for the first week, since a hard stream of water at this stage can wash the seed into clumps.