May is the most important planting month for most North American gardeners. Last frosts are behind zones 5–8, the soil has finally warmed, and summer crops need to go in now to produce before fall.
Zones 3–4 (Minnesota, Maine, Upper Michigan)
Last frost date: May 15–30. Cold-hardy crops only in early May: kale, spinach, lettuce, peas, radishes, carrots. Hold tomatoes and squash until Memorial Day. Start tomatoes and peppers indoors now if you haven't (or buy transplants).
Zones 5–6 (Ohio, Pennsylvania, Kansas, Virginia)
Last frost: April 15 – May 1. May is prime time. Transplant tomatoes, peppers, eggplant after May 1. Direct sow: beans, cucumbers, squash, basil, beets. Continue succession sowing lettuce and radishes.
Zones 7–8 (North Carolina, Tennessee, Oregon coast, Pacific Northwest)
Warm-season crops should already be in the ground. May plantings: warm-weather herbs (basil, oregano, cilantro succession), second round of cucumbers and squash. Watch for aphids on roses and brassicas as temperatures climb.
Zones 9–10 (Phoenix, Houston, Southern California, South Florida)
Summer heat is arriving. Last chance for tomatoes (they stop setting fruit above 95°F). Switch to heat-adapted crops: okra, Armenian cucumber, sweet potato, Malabar spinach. Install drip irrigation before it gets brutal.
