If you haven’t started seeds yet this spring, May can feel like you’ve already missed the boat. But most heat-loving crops don’t want to go into the ground until the soil is warm anyway, which means may seed starting is actually a pretty good time. And for gardeners in the coldest zones where it’s still chilly, it’s prime time for indoor sowing. These are the seeds worth starting in May, whether you’ve begun sowing already or not. Some crops (beans, squash, cucumbers) do just as well or better sown directly now, depending on your climate. Just pick the right varieties and don’t push them out too early.
Why May Seed Starting Is Ideal for Warm-Weather Vegetables
May brings longer days and rising soil temperatures. Many vegetables that thrive in heat actually require warm soil to germinate. Cold, wet ground rots seeds. So waiting until May often gives you a better success rate than rushing in April. For northern gardeners with short seasons, may seed starting indoors under lights can still produce a full harvest before frost returns. The key is matching each crop’s temperature needs with your local conditions. A simple soil thermometer costs under $10 and takes the guesswork out of planting.
As always, the right varieties to sow will depend on your zone. Check the specific requirements on the seed packets to make sure you don’t get your seeds in the ground too early or too late. Here are seven crops that perform especially well when planted in May.
1. Bush Beans
Direct sow bush beans once soil reaches 60°F (16°C). Beans germinate quickly in warm soil (usually within a week) and most bush varieties start producing in under two months. There’s no real advantage to starting them indoors because bean seedlings don’t transplant well, and the seeds are large enough that direct sowing is simple. Although they like mild temperatures, their short season means you can still grow pretty reliably in May.
Wait until your soil has warmed to about 60°F (16°C) before planting. Cold, wet soil tends to rot bean seeds before they sprout. Push each seed about an inch deep, spaced four inches apart, and you should see them break the surface within a week. Bush beans fix nitrogen in the soil through a symbiotic relationship with rhizobia bacteria, so they actually improve the ground for the next crop. Plan to sow a second batch in early July for a continuous harvest into September.
2. Cucumbers
Sow cucumbers indoors in plantable pots or direct sow into warm soil. Sowing cucumbers indoors in biodegradable pots about three weeks before your last frost date gives you a head start without the transplant damage (if you haven’t passed your last frost date yet). But direct sowing into warm soil works just as well, and May is a great time. Plant seeds about half an inch deep (two per spot), and thin to the strongest seedling once they’re a few inches tall.
Keep in mind that cucumbers are heavy feeders and need plenty of water once they start vining. Also don’t forget to place your supports at planting time to avoid any root damage later on. Cucumbers are about 96% water, so inconsistent watering can cause bitter fruit. Aim for 1–2 inches of water per week, applied slowly at the base. Mulching with straw or shredded leaves helps retain moisture and keeps the soil temperature steady.
3. Summer Squash
Direct sow squash seeds once soil stays above 65°F (18°C). These plants are prolific, and they grow fast enough that a May sowing still gives you plenty of time to harvest. Direct sow summer squash seeds once the soil is consistently above 65°F (18°C). Plant them about an inch deep spaced three feet apart, dropping two seeds per spot and thinning to one. Germination should take less than a week in warm soil.
Starting indoors is possible but usually unnecessary since the seeds catch up quickly when sown directly, and squash seedlings don’t love being moved. Once they’re in, a single plant can easily spread three feet across. Plan accordingly, or the vines will plan for you. Summer squash varieties like ‘Yellow Crookneck’ and ‘Zucchini’ can produce 6–10 pounds of fruit per plant over the season. Harvest when fruits are 6–8 inches long for the best texture and flavor.
4. Basil
Wait until nighttime temperatures hold above 50°F (10°C) to sow basil. May is the ideal time to start basil from seed, whether indoors or directly outside (once nighttime temperatures stay above 50°F). Basil is extremely cold-sensitive, and even a few nights in the low 40s can stunt young plants or kill them outright. For direct sowing, press seeds lightly into the soil surface and keep them moist.
If you’re starting indoors, sow seeds in trays under grow lights and transplant outdoors once the weather has warmed. Harden them off gradually over a week, since basil that goes from a warm indoor setup to full outdoor sun tends to wilt before recovering. ‘Italian Genovese’ is the classic variety for cooking, and it’s hard to argue with the flavor. Thai basil holds up better in heat and adds a sharper, anise-like edge to dishes. Or you can go for a pop of color with ‘Purple Petra’. Basil seeds are tiny—about 600 seeds per gram—so handle them gently and avoid burying them too deep.
5. Sunflowers
Direct sow sunflower seeds about an inch deep in a sunny spot. Most sunflower varieties go from seed to bloom in about 70 days, which means a May planting will give you midsummer flowers. Push seeds one inch deep, spaced six inches apart, then thin to the strongest seedlings once they reach four inches tall. Sunflowers develop a long taproot early, so transplanting often sets them back or kills them. Direct sowing is the only reliable method.
Tall varieties like ‘Mongolian Giant’ can reach 12–14 feet and need wind protection. Plant them along a fence or in a block where they can support each other. A snapped stem is a disappointing way to lose a sunflower you’ve been watching all season. Sunflowers also attract pollinators and beneficial insects, making them a smart companion for vegetable beds. For cut flowers, choose branching varieties that produce multiple stems per plant.
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6. Corn
Corn needs warm soil (60°F or more) and consistent heat to germinate. May is a practical sowing window for corn in several regions. Plant seeds one inch deep, spaced eight to twelve inches apart in rows. The most important thing with corn is pollination: you need at least four rows (or a block) rather than a single long row. Corn is wind-pollinated, and planting in a block of at least 4×4 feet ensures good coverage. Each silken strand must receive a grain of pollen to form a kernel, so a sparse planting leads to bare cobs.
Corn is a heavy feeder, especially of nitrogen. Work in plenty of aged compost or a balanced fertilizer before planting. Water deeply once a week, more if the weather is dry. Varieties like ‘Golden Bantam’ or ‘Silver Queen’ are reliable for home gardens. Succession planting every two weeks through early June extends the harvest window. Expect about 60–80 days from sowing to harvest for most sweet corn varieties.
7. Melons (Cantaloupe and Watermelon)
Melons are true heat lovers and should not be planted until soil temperatures reach at least 70°F (21°C). In many regions, May provides that warmth. Direct sow seeds half an inch deep, three per hill, with hills spaced four to six feet apart. Thin to the two strongest seedlings once they emerge. Melons have a long taproot and dislike transplanting, so direct sowing is preferred.
Watermelons need 70–90 days to mature, so choose short-season varieties if your summer is short. ‘Sugar Baby’ watermelon matures in about 75 days and produces 8–10 pound fruits. Cantaloupes like ‘Athena’ are ready in 70–80 days. Melons require consistent moisture during fruit set and development, but reduce watering as fruits ripen to concentrate sweetness. Black plastic mulch can help warm the soil and suppress weeds, giving melons a strong start in May.
General Tips for Successful May Seed Starting
Whether you’re direct sowing or starting indoors, a few practices improve your odds. First, always check your seed packets for days to maturity and compare that to your average first fall frost date. If a crop needs 80 days and your first frost comes in early September, a late May sowing might be risky. Second, water seeds gently—a heavy stream can wash them away or push them too deep. Use a fine spray or a watering can with a rose attachment.
Third, harden off any indoor-started seedlings gradually over 7–10 days. Move them outside for a few hours in shade, then increase sun exposure daily. This prevents transplant shock and sunburn. Fourth, consider using row covers or cloches to protect young plants from late cold snaps or pest insects. Cutworms and cucumber beetles are active in May, so a lightweight fabric barrier can save your seedlings.
Finally, keep a garden journal. Note soil temperatures, planting dates, and weather patterns. Over time, you’ll learn exactly when your particular microclimate is ready for each crop. That knowledge is more valuable than any generic calendar date.
May is not a consolation prize for late starters—it’s the sweet spot for many of the most rewarding garden vegetables. With warm soil, long days, and a little planning, your may seed starting efforts will yield a bountiful summer harvest. Get those seeds in the ground, and watch them take off.
