What to Plant in May: The Direct-Sow Window for 20 Vegetables and Summer Flowers
May is the pivotal month in the US gardening calendar. For most of the country, the last frost has passed, the soil is warming fast, and the list of plants you can safely put outside now includes the tender crops and summer annuals that have been waiting on windowsills since late winter. This is the month gardeners live for.
For gardeners in Zone 5 and 6, the last frost typically clears by the first or second week of May — often right around Mother’s Day — opening the full planting list in a single glorious stretch. In Zone 7 and warmer, you are already well into the season and the focus shifts to heat-tolerant succession sowing to keep harvests coming all summer. Zones 3 and 4 gardeners should still exercise caution: your last frost can run all the way into late May, so watch the five-day forecast and keep frost cloth within reach.
Whatever your zone, May rewards decisive action. Plants put out in warm soil with room to run will race ahead of those planted in June. This guide takes you through everything — zone by zone, crop by crop — so you can make the most of every day the season gives you.
Already caught up on spring tasks? Read our complete what to plant in spring guide for anything you may still need to complete from earlier in the season.
Zone-by-Zone May Planting Overview
Your USDA Hardiness Zone is the single most important variable in May planning. The table below gives you a quick-reference framework; the sections that follow fill in the detail.
| Zone | Typical Last Frost Window | May Priorities |
|---|---|---|
| Zone 3–4 (MN, ND, northern WI, high elevation West) | Mid-to-late May | Harden off transplants carefully; direct sow cool-season crops in early May only; hold all tender vegetables until frost-free nights are confirmed by your local forecast |
| Zone 5–6 (OH, IN, PA, most of the Midwest and Northeast) | Early-to-mid May | Full planting list opens after Mother’s Day; transplant tomatoes, basil, zucchini, peppers, and all summer annuals; direct sow beans, sweetcorn, and sunflowers |
| Zone 7–8 (VA, NC, TN, Pacific Northwest, Pacific Coast) | Late March to mid-April (already past) | Heat lovers actively growing; focus on succession sowings of beans and salad crops; shade cool-season plants if soil temperatures exceed 85°F |
| Zone 9–10 (CA, Gulf Coast TX, FL, SW desert) | Winter only | Cool-season crops finishing; transition to heat-tolerant summer crops (okra, sweet potato, Southern peas, Armenian cucumber); water management becomes the primary challenge |
Last frost date ranges sourced from NC State Cooperative Extension’s frost date database, cross-referenced with USDA Zone boundaries.
Planting Out After Last Frost: Tender Crops
The last frost date is a statistical probability, not a guarantee — it represents the date on which there is a 50% historical chance of frost. For transplanting tender vegetables, use it as a starting point but verify with two key measurements: soil temperature and overnight air temperature. The calendar is a guide; the thermometer is the authority.
Tomatoes
Tomatoes are the signature May planting event for most US gardeners. Get the timing right and you will set up a productive summer. Rush it by even a week and one cold night can set plants back by three weeks.
- Soil temperature: must reach 60°F at 4-inch depth. Below this, root activity slows dramatically and nutrient uptake stalls. A cheap soil thermometer is one of the best investments a vegetable gardener can make.
- Night temperature: confirm three consecutive nights above 50°F before transplanting. A single night at 45°F will not kill tomatoes but will check growth and can cause chilling injury that shows up as yellowing a week later.
- Planting depth: bury the stem up to the lowest set of true leaves. Tomatoes produce adventitious roots all along the buried stem, giving the transplant a far stronger root system than if planted at nursery-pot depth.
- Stake at planting: insert cages or bamboo canes at the time of transplanting, before roots spread. Inserting support later disturbs roots and invites disease entry points.
- Hardening off: a 7–10 day hardening process — setting seedlings outdoors for progressively longer periods — is essential before final transplanting. Skip this and even strong plants will show leaf scorch and wilt from the transition.
For full guidance including variety selection by zone, spacing, watering schedules, and mid-season feeding, see our complete tomato growing guide.
Basil
Basil is even less cold-tolerant than tomatoes. A night below 50°F will not kill established basil, but it will turn the leaves black-edged and stunt the plant for days — a setback that takes two to three weeks to recover from. Wait for warm, settled nights before planting out.
- Soil temperature: 60°F minimum — the same benchmark as tomatoes.
- Choose the warmest, most sheltered spot in the garden. A south-facing bed against a sun-warmed wall is ideal for basil, especially in Zone 5.
- Plant in the morning on a calm, overcast day to minimize transplant stress.
- Pinch out the growing tip at planting to encourage bushy, branching growth. Left to run, basil produces a single tall stem that goes to flower quickly.
Our full basil growing guide covers all 12 commonly grown varieties, succession sowing schedules, and harvesting techniques that extend production through summer.
Zucchini and Summer Squash
One or two zucchini plants is genuinely sufficient for most families. These are extraordinarily productive — a single healthy plant in good soil will supply more zucchini than most households can eat by midsummer. Plant after last frost in full sun with moisture-retentive, rich soil. Space at least 3 feet apart; these plants spread considerably. Water at the base rather than the leaves to reduce the risk of powdery mildew, which is the most common problem in warm, humid summers.
Cucumbers
Cucumbers require warm soil — ideally 65°F or above — and consistent moisture. Direct sow or transplant after your last frost date. Bush varieties are compact and suit large containers or raised beds; vining types are more productive but need a trellis, fence, or sturdy cage. Irregular watering (wet-dry-wet cycles) is the primary cause of bitter cucumbers, so aim for even soil moisture throughout the growing season.
Winter Squash and Pumpkins
Winter squash and pumpkins are long-season crops — most varieties need 90–110 days to reach maturity. In Zone 5 and 6, starting seeds indoors in late April and transplanting in early May gives them the head start necessary to mature before the first autumn frost. In Zone 7 and warmer, direct sowing in May is perfectly adequate. Allow 6–8 feet of spreading space per plant; growing on a trellis vertically is an option for smaller gardens.
Runner Beans and French Beans
Both are fast-growing, high-yielding crops that reward May sowing generously. Direct sow after last frost, 2 inches deep, 6 inches apart in rows. Runner beans need a trellis, cane wigwam, or fence 6–8 feet tall. French (bush) beans are more compact and need no support. The golden rule with all beans: the more you pick, the more the plant produces. Check plants every two days once harvest begins and never let pods go stringy on the plant.
Sweetcorn
Sweetcorn is wind-pollinated, which makes planting geometry critical. Always plant in a block — at minimum 4 rows by 4 plants (16 plants total) — rather than a single long row. In a row, pollen from the tassels drifts sideways rather than falling down onto the silks below, resulting in poorly filled cobs. In a compact block, every plant is surrounded by pollen sources on multiple sides. Direct sow 1 inch deep, 12 inches apart, after soil reaches 60°F. In Zone 5–6, this typically means mid-to-late May.
Container and Hanging Basket Planting
May is the official start of hanging basket and container season across most of the US. Once night temperatures are reliably above 50°F — typically mid-May in Zone 6, earlier in Zone 7 and warmer — tender annuals are safe to plant up and display outdoors permanently.
The Thriller / Filler / Spiller Formula
For a visually professional hanging basket or large container, the three-component planting formula works reliably:
- Thriller: a tall, structural centrepiece plant that provides height and visual impact. Options: upright fuchsia, purple fountain grass, tall single-stemmed calibrachoa, spiky dracaena, or a standard geranium.
- Filler: mid-height plants that fill in the volume around the thriller. Options: bacopa, sweet alyssum (lobularia), impatiens (shade), verbena, or zonal geraniums.
- Spiller: trailing plants that cascade over the rim and soften the container edge. Options: trailing lobelia, calibrachoa, ivy, trailing nasturtium, or bacopa.
For a standard 14-inch basket, use 1 thriller, 3–4 fillers, and 3–4 spillers. Plant firmly, removing air pockets around roots, and water thoroughly immediately after planting.
Best May Container Plants
- Petunia: the most reliable container performer from May to first frost. Wave, Supertunia, and Tidal Wave series cascade generously and are near self-cleaning. Feed weekly with a high-potassium liquid fertiliser to keep blooms continuous. See our petunia growing guide for series comparisons, deadheading technique, and how to revive the mid-summer slump that affects many petunia varieties.
- Bacopa (Sutera cordata): tiny white or pink flowers on naturally trailing stems. Nearly self-cleaning — spent flowers drop naturally without deadheading. Tolerates partial shade better than most summer annuals, making it ideal for east or north-facing baskets.
- Trailing Lobelia: electric blue, white, or bicolour cascading flowers. Prefers partial shade in Zone 7 and warmer; tolerates full sun in cooler zones. Cut the entire plant back by a third in late July if it becomes woody or sparse — it will flush with new growth and flower again in August.
- Calibrachoa (Million Bells): miniature petunia relative with outstanding heat tolerance and no deadheading required. Particularly valuable in Zone 8 and warmer where standard petunias flag in summer heat. Available in an enormous colour range including bicolours and doubles.
- Fuchsia: classic hanging basket choice for shaded or north-facing positions. Not frost-hardy — in Zone 5, keep basket-grown fuchsias under cover until late May and be prepared to bring them inside if an unexpected frost is forecast.
- Trailing Nasturtium: edible flowers and leaves, extremely easy to grow, and an outstanding natural spiller. Thrives in poor, dry soil — overly rich compost produces lush foliage at the expense of flowers.
Watering and Feeding Containers
Hanging baskets and pots dry out far faster than border soil. In hot weather above 80°F, a 14-inch basket may need watering twice daily. Check moisture by inserting a finger 2 inches into the compost — if it feels dry at that depth, water until water flows freely from the drainage holes. Never allow a basket to sit in standing water in a saucer for more than 30 minutes.
Feed every week with a balanced liquid fertiliser for the first four to six weeks after planting, then switch to a high-potassium feed (tomato fertiliser works well) once flower buds are visible. Potassium drives flower and fruit production; nitrogen, which dominates balanced feeds, drives leafy growth. Making this switch at the right time is the single biggest factor in whether a container delivers a continuous season of flowers or a flush then a fade.
May Flower Sowing Direct Outdoors
May is one of the best months for direct sowing fast-growing annuals. The soil is warm, germination is rapid, and plants started now will hit peak bloom in July and August — exactly when gardens need the most colour.
Sunflowers
Direct sow sunflowers in May for blooms in July and August. Sow 1 inch deep, 12 inches apart for standard varieties (24 inches for giant types over 8 feet tall). Germination takes 7–10 days in warm soil. Thin to the strongest seedling when plants reach 3 inches. Sunflowers are drought-tolerant once established but need consistent moisture during germination and the first month of growth. They are among the easiest direct-sow crops and one of the most rewarding: a cutting garden with a dozen sunflower plants sown in May will deliver armfuls of stems from late July onwards.
Zinnias
In Zone 6 and warmer, direct sow zinnias after your last frost date. Zinnias hate root disturbance, so direct sowing consistently outperforms transplanting from pots. Sow 1/4 inch deep in well-prepared, well-drained soil in full sun. Pinch out the growing tip when plants reach 6 inches to promote branching and multiply flower production. Zinnias are among the fastest annuals from seed — 8–10 weeks to first bloom from a May sowing means flowers by late July.
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→ View My Garden CalendarNasturtiums
Nasturtiums are the hardest-working easy annual in the May sowing list. Direct sow after last frost, 1/2 inch deep, 10–12 inches apart. Both flowers and leaves are edible — peppery and excellent in salads. Trailing varieties (‘Jewel of Africa’, ‘Tip Top Mahogany’) are outstanding for containers and banks; compact types work in borders and vegetable beds. They thrive in poor, dry soil — rich growing conditions push leaf production at the expense of flowers.
Cosmos
Few annuals are as generous or as long-blooming as cosmos. Direct sow after last frost, thinning to 12 inches apart. Plants flower from July onwards and continue through the first autumn frost — a five-to-six month display from a single May sowing. The finely cut, feathery foliage adds an airy meadow quality to any planting. Cosmos tolerates dry conditions well once established; overwatering produces lush foliage and fewer flowers.
Marigolds
Marigolds are the classic companion plant for the vegetable garden. Their scent discourages aphids, whitefly, and root nematodes, while their open single flowers attract beneficial insects and pollinators throughout the summer. Direct sow or plant out transplants near tomatoes, beans, cucumbers, and squash from May onwards. For the evidence behind companion plant combinations that actually work — and combinations to avoid — see our companion planting guide.
Succession Sowing: Preventing Gaps and Gluts
One of the most valuable gardening habits to build in May is succession sowing — sowing small quantities of the same crop every few weeks rather than a large single batch. This approach smooths out harvests, prevents the feast-or-famine cycle that frustrates so many kitchen gardeners, and keeps your growing space productive for far longer.
Key crops for May succession sowing:
- Lettuce: sow a short row every three weeks. A 6-foot row of cut-and-come-again lettuce supplies more than enough for a household when harvested regularly. In Zone 7 and warmer, choose bolt-resistant varieties for May sowings: ‘Jericho’, ‘Muir’, and ‘Nevada’ are all recommended by Purdue Cooperative Extension for summer heat tolerance.
- Radishes: the fastest crop in the vegetable garden — ready to pull in 25–30 days from sowing. Sow every two weeks for a continuous supply through early summer. Pull as soon as roots reach the right size; left in the ground even a few days too long, they become woody, hollow, and unpleasantly sharp.
- Salad leaves and mixed greens: scatter sow in containers or dedicated short rows every three weeks. Cut plants at 4 inches tall and they will regrow 2–3 times before going to seed.
- Cilantro: bolts to seed rapidly in warm weather. Sow small batches every three weeks for a steady leaf supply. Letting one plant bolt is worthwhile — the seeds (coriander) are an additional harvest and the flowers attract beneficial insects.
- Spinach: in Zone 5–6, May is the last practical month for spinach until autumn, as it bolts quickly once day length increases and temperatures exceed 75°F. Sow immediately and harvest young leaves before the heat builds.
Penn State Extension notes that succession planting is one of the most under-used techniques in home vegetable gardens despite being the single most effective way to maintain a consistent supply of fresh salads and cut herbs without waste or glut.
The Chelsea Effect: May Garden Inspiration
The RHS Chelsea Flower Show, held in London during the last week of May, is the most influential garden event in the world — and even for US gardeners growing USDA zones away from the British Isles, it is worth paying close attention. The trends showcased at Chelsea directly shape what plant breeders develop, what nurseries stock, and what gardeners everywhere plant over the following two to three years.
Trends worth watching from recent Chelsea shows:
- Climate-resilient planting: drought-tolerant perennials — salvias, sedums, agastache, echinacea — are displacing water-intensive annual bedding in show gardens. This shift is already well underway in US horticulture.
- Edible ornamentals: the hard line between food garden and flower garden is dissolving at Chelsea and in gardens everywhere. Expect more mixed productive planting rather than segregated vegetable plots hidden at the back.
- Native plant integration: US gardeners have led this movement for a decade, but Chelsea has caught up fast. Native plants support local pollinators, reduce inputs, and once established, largely look after themselves.
- Bold, saturated colour: hot oranges, deep burgundies, and jewel-toned purples have replaced the muted, greyed palettes that dominated the 2010s. May is the perfect month to experiment with bold colour combinations in containers before committing to border planting.
Oregon State University Extension notes that plants introduced at major show events often reach mainstream US nurseries within 18–24 months — so if you spot a variety you love at a garden centre in late May, it is worth buying it now rather than assuming it will be available next year.
Frequently Asked Questions
What can I plant outside after last frost in May?
After your last frost date in May, you can transplant all tender vegetables: tomatoes, peppers, eggplant, basil, zucchini, cucumbers, squash, and beans. You can also direct sow sweetcorn, sunflowers, zinnias, nasturtiums, cosmos, and marigolds. All summer bedding annuals — petunias, calibrachoa, lobelia, fuchsia, bacopa — can go into containers and hanging baskets permanently once frost risk has passed.
Can I plant tomatoes in May?
Yes — for most US gardeners, May is the ideal month for transplanting tomatoes outdoors. The two conditions that must be met are a soil temperature of at least 60°F (measured 4 inches deep) and three consecutive nights above 50°F. In Zone 5 and 6 this is typically met in the first or second week of May. In Zone 3–4, you may need to wait until the final week of May or even early June. Never skip hardening off, regardless of zone.
What flowers bloom fastest from a May sowing?
Nasturtiums are the speed champions — they can produce their first flowers 6–8 weeks after direct sowing, meaning July blooms from a May start. Zinnias follow at 8–10 weeks, and marigolds bloom in 8–10 weeks from a May sowing as well. Sunflowers take slightly longer at 10–12 weeks depending on variety. All four can be direct-sown in May without any indoor starting and will provide colour through to autumn.
Can I hang baskets outside permanently in May?
In Zone 6 and warmer, yes — once your last frost has passed, tender annuals in hanging baskets are safe outdoors permanently. In Zone 5, wait until after Mother’s Day and check the 10-day forecast for any lingering cold nights. In Zone 3–4, keep baskets under cover or bring them inside if a frost warning is issued — your last frost can run all the way into late May, and a single frost will kill unprotected tender annuals overnight.
Sources
- NC State Cooperative Extension — Frost Dates and Vegetable Planting Calendar for North Carolina
- Purdue Cooperative Extension — Vegetable Planting Guide and Recommended Planting Dates (HO-32-W)
- Penn State Extension — Growing Vegetables in the Home Garden
- Oregon State University Extension — Vegetable Gardening in Oregon (EC 871)
