What to Plant in May in Pennsylvania

May is the month Pennsylvania gardeners wait all year for. The frost risk finally drops off, soil temps climb into the 60s and 70s, and every warm-season crop you’ve been babying under grow lights can go outside. If you only garden one month of the year, this would be it — but please don’t do that, because there’s great planting to do all season long.

Here’s the thing about May in PA, though: the state is big enough that early May in Philadelphia and early May in Scranton are practically different seasons. Zone 7a gardeners are transplanting tomatoes the first week while zone 5b gardeners are still watching for frost warnings. Know your zone, check your local frost dates, and you’ll be fine.

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When to Transplant the Big Three: Tomatoes, Peppers, and Eggplant

This is the main event. The crops everyone asks about, the ones that define a PA summer garden, and the ones that need the right timing more than anything else you’ll grow.

Tomatoes

Tomatoes need nighttime temps consistently above 50°F and soil temps above 60°F. In most of PA, that means mid-May is your safe transplant window. Zone 7a gardeners can push to early May. Zone 5b and mountain gardeners should target the last week of May or even early June.

Plant tomatoes deep — bury two-thirds of the stem. Tomatoes grow roots all along the buried stem, which creates a stronger, more drought-resistant plant. Dig a deep hole or a trench and lay the stem sideways with just the top few leaf sets above ground.

Space indeterminate varieties (the ones that keep growing all season) 24–36 inches apart and stake or cage them at planting. Don’t wait until they’re flopping over — getting the cage on early saves you from wrestling a tangled 5-foot plant in July.

The first real instinct when you set them out is to water and fertilize like crazy, but hold off on heavy feeding for the first two weeks. Let the roots establish. Overwatering right after transplant is actually one of the most common early mistakes — keep the soil moist but not soaked.

Peppers

Peppers are even less cold-tolerant than tomatoes. They stall in cool soil and won’t recover their momentum if they get chilled early. Wait until nighttime temps are reliably above 55°F — that’s usually a week after your safe tomato date.

For most of PA, that means mid-to-late May. Zone 7a can go mid-May. Zone 5b should wait until late May or the first days of June.

Space sweet peppers 18 inches apart, hot peppers 12–15 inches. Peppers don’t need to be planted deep like tomatoes — set them at the same depth they were in the pot. Mulch around the base to keep soil warm and conserve moisture.

Eggplant

Eggplant wants the warmest conditions of the three. It’s originally a tropical plant and absolutely hates cool nights. Don’t rush it. Wait until nighttime temps are consistently above 55°F — the same window as peppers or even a few days later.

Plant 18–24 inches apart. Eggplant in PA benefits from black plastic mulch to warm the soil, especially in zones 5b and 6a where nights stay cool into June. Japanese varieties (like Ichiban) tend to produce more reliably in PA’s shorter season than traditional Italian globe types.

What to Direct Sow Outdoors in May

Once the soil warms into the 60s, a whole category of crops becomes available that you couldn’t plant in March or April.

Beans (Bush and Pole)

Beans need soil temps above 60°F to germinate without rotting. In zone 7a, that’s early May. For zones 6a–6b, mid-May. Zone 5b, late May.

Plant 1 inch deep, 3–4 inches apart for bush beans, 4–6 inches apart for pole beans. Don’t bother starting beans indoors — they transplant poorly and germinate so fast in warm soil (7–10 days) that there’s no advantage to it. If you want a steady harvest all summer, succession plant bush beans every two weeks through the end of June.

Corn

Corn needs warm soil (above 60°F) and plenty of space. Plant in blocks of at least 4 rows rather than long single rows — corn is wind-pollinated and needs neighboring plants to pollinate properly. Thin rows produce ears with missing kernels.

Sow 1 inch deep, 8–12 inches apart, in rows 30–36 inches apart. Corn is a heavy feeder that especially loves nitrogen. Side-dress with compost or a nitrogen-rich fertilizer when plants are knee-high.

For the sweetest varieties, try SugarEnhanced (SE) or Supersweet (sh2) types. Synergistic varieties (like Honey Select) give you a mix of both textures. Just don’t plant supersweet corn near standard sweet corn — cross-pollination makes both taste starchy. Keep different types at least 250 feet apart or stagger planting times by two weeks.

Cucumbers

Cucumbers are fast growers that go from seed to harvest in 50–70 days, making mid-May sowing ideal even for zone 6a. Plant seeds 1 inch deep, 12 inches apart for trellised plants or 36 inches for ground spreaders.

Trellising cucumbers saves a ton of space, improves air circulation (which reduces powdery mildew — a constant problem in PA’s humid summers), and produces straighter, cleaner fruit. A simple cattle panel or section of wire fencing works great.

Squash and Pumpkins

Summer squash (zucchini, yellow squash) matures fast — 45–55 days — and produces so aggressively that two plants can overwhelm a family of four. Seriously, plant fewer than you think you need.

Winter squash and pumpkins need more time (80–120 days) and a lot more space. Plant in hills 4–6 feet apart. If you’re growing jack-o-lantern pumpkins for Halloween, count backward from October 31 — plant by mid-May for 100-day varieties.

Sow all squash 1 inch deep in warm soil. These seeds rot quickly in cold, wet conditions, so don’t rush it in zones 5a–5b.

Melons

Watermelons and cantaloupes need the warmest soil and longest season of any common garden crop. In zone 7a, direct sow in mid-May. In zones 6a–6b, start seeds indoors 3–4 weeks early or transplant purchased starts in late May. Zone 5b gardeners should use transplants and consider black plastic mulch to boost soil temps.

Short-season varieties are your best bet in PA. Sugar Baby watermelon (80 days) and Minnesota Midget cantaloupe (65 days) mature reliably even in zone 6a. Full-size watermelons (90+ days) are a gamble north of zone 6b.

Herbs

May is when you can finally plant the warm-season herbs outdoors:

• Basil — the most popular warm herb and the most frost-sensitive. Plant after all frost risk has passed. Pinch the growing tips regularly to keep plants bushy and delay flowering. Once basil flowers, the leaves lose flavor.
• Dill — direct sow in the garden; it doesn’t transplant well. If you grow it near tomatoes, you’ll also attract beneficial parasitic wasps.
• Cilantro — sow now for a spring harvest, but expect it to bolt by late June. Succession plant every 3 weeks if you want continuous supply.

Perennial herbs like rosemary, thyme, oregano, and sage can be transplanted outdoors in May too if you started them from seed or purchased plants. These are tough once established and come back year after year in most PA zones.

Succession Planting: Keep the Spring Crops Going

Don’t stop planting cool-season crops just because the warm-season stuff is finally going in. Succession planting is how you avoid the classic mistake of having everything ripen at once followed by weeks of nothing.

• Lettuce — sow a short row every 10–14 days through mid-May. Switch to heat-tolerant varieties (like Jericho or Muir) as temps climb. Lettuce planted after late May will likely bolt before it’s harvestable.
• Radishes — keep sowing until mid-May. They’ll bolt in June heat, so this is your last window until fall.
• Beets and carrots — sow another round in early May for a June/July harvest. These handle the transition to warm weather better than lettuce.

Container Planting

If you’re gardening on a patio, balcony, or deck, May is when container gardening really takes off. Everything that goes in the ground in May can go in containers — you just need to choose the right pot size.

• Tomatoes — minimum 5-gallon container, 10-gallon is better. Determinate (bush) types like Patio, Celebrity, or Roma work best in pots.
• Peppers — 3-to-5-gallon containers work great. Peppers actually perform really well in pots because the container soil stays warmer than ground soil.
• Herbs — most herbs do fine in 1-to-3-gallon pots. Group a few together in a large planter near your kitchen door.
• Cucumbers — need at least a 5-gallon pot and a small trellis. Bush varieties like Spacemaster are bred for containers.

Container plants dry out faster than in-ground plants and may need watering every day during PA’s hot summer stretches. Self-watering planters or drip irrigation on a timer save you from losing plants to a single missed watering day.

Soil and Planting Tips for May

Soil Temperature Check

Don’t trust the air temperature — check the soil. A soil thermometer takes the guesswork out of timing. Insert it 4 inches deep in the morning (not after a sunny afternoon) for an accurate reading. You’re looking for:

• 50°F — tomatoes can survive, but 60°F is better for real growth
• 60°F — beans, corn, cucumbers, squash. The floor for warm-season crops.
• 65°F+ — melons, peppers, eggplant. These take off once soil hits this range.

Penn State Extension’s vegetable planting guide has a detailed list of soil temperature minimums for every common crop.

Mulching

After transplanting warm-season crops, wait 1–2 weeks before mulching. You want the soil to warm up fully first. Once plants are established and the soil is warm, apply 2–3 inches of straw, shredded leaves, or wood chips around (not touching) the stems. Mulch conserves moisture, suppresses weeds, and keeps soil temperatures more stable.

For tomatoes, keep mulch a few inches away from the stem to prevent moisture-related diseases like early blight.

Watering at Transplant

Give every transplant a thorough soaking at planting time — enough to settle the soil around the roots and eliminate air pockets. Then ease off to 1 inch per week (including rain). Overwatering new transplants encourages shallow root growth and can cause root rot, especially in PA’s clay soils.

According to The Old Farmer’s Almanac planting guide, the most common mistake new gardeners make is overwatering, not underwatering. If the top inch of soil feels moist, wait.

May Planting Calendar at a Glance

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