The month of May will bring Spring weather to almost all regions of the Northern Hemisphere. May is the time to direct sow warm-weather vegetable seeds in all gardens. Once the last frost is past, vegetable seedlings can go into the garden as well.
May planting and transplanting tips
- Few seeds will germinate if the soil temperature is below 45ºF (7ºC) and warm-weather crops will not thrive until the night temperatures stay consistently above 50ºF (10ºC). Follow the high and low temperatures for several days if you are unsure if the time is right to begin sowing and planting out warm-season crops.
- If you do get started and temperatures unexpectedly dip, use horticultural fleece or cloches to protect summer veggies from danger.
- You can minimize transplant shock if you hold off putting melons and summer and winter squash seedlings in the garden until 10 days after the date of the last expected frost. Peppers and eggplants can be transplanted into the garden two to three weeks after the last frost.
- Herb starts like dill, oregano, sweet marjoram, cilantro, rosemary, sage, and thyme can be transplanted into the garden this month. Make sure the weather is settled warm before you plant out basil and lemongrass.
Here is a kitchen garden guide for warm regions–growing zones 7-11– for the month of May:
Greenhouse and cold frame to-dos in May
- Sow successions of tender vegetables such as tomatoes, peppers, cucumbers, and runner beans to plant out later.
- Plant greenhouse tomato plants in large pots, or plant them in grow bags.
- Water and feed tomatoes, cucumbers, and peppers, never letting the soil dry out. Remove side-shoots from tomatoes.
- Attach slings or nets to greenhouse melons as they swell.
- Introduce biological controls to keep down pests such as greenhouse whiteflies and spider mites.
Vegetable garden to-dos in May
- Start sowing vegetables without protection if the soil and nighttime temperatures have warmed.
- Thin beets, carrots, lettuce, radishes, spinach, and other half-hardy and hardy seedlings planted late last month. As crops are harvested, plant successions spring crops or start introducing summer crops.
- Early in the month, prepare outdoor sites for cucumbers, squashes, and tomatoes. Erect supports for runner beans, and place stakes, poles, and trellises in place for tall and climbing crops.
- Stake tomatoes and tie them gently to stakes.
- Remove cloches from broad beans, carrots, and peas.
- Mid-month sowing: sow seeds of beans, lima beans, corn, okra, squash, cucumber, cantaloupe, Chinese cabbage, and other tender vegetables and herbs after temperatures have reached the 70sF.
- Sow cucumbers in mounds enriched with plenty of well-rotted manure and compost.
- Set out transplants after mid-month: tomato, eggplant, pepper, and sweet potato.
- Set out sweet potato slips on a cloudy day. Form a little mound of soil over young potato shoots to protect them from frost.
- Pinch out the tips on broad beans to encourage a good pod set and to deter attack from aphids.
- Make sowings of salad crops and summer spinach.
- Stop watering onions, garlic, and shallots when the foliage begins to turn yellow.
Harvesting early crops in May
- Start picking broad beans when the pods are finger thick.
- Continue to cut asparagus. As the asparagus harvest ends, cut back female plants with berries.
- When peas stop producing, cut vines to ground (do not pull allowing their roots to fix nitrogen in the soil). Replace early cool-weather crops with summer crops.
Succession planting in May
- Make successional sowings of early crops: beetroot, carrots, lettuces, and turnips. Make successive sowing of lettuce, salad crops, and summer spinach, turnips, runner beans, green beans, endive, radishes, and kohlrabi.
Late month sowing and transplanting in May
- Sow sweet corn outdoors in mild areas when further frost is unlikely. Most vegetables can be sown now, so check the packets.
- Sow French and runner beans, and pole beans, long-rooted beets, sea kale, salsify, and sweet corn.
- Plant out late-summer cauliflowers and in the north Brussels sprouts. Plant out vegetable seedlings such as cabbages, cauliflowers, celery, sweet corn, tomatoes, and marrows. Plant outdoor tomatoes, and tie them gently, but firmly, to stakes to secure them.
Herb garden in May
- Plant or pot up basil seedlings.
- Take cuttings of pot marjoram, rosemary, sage, and thyme.
- Divide and transplant perennial herbs.
- Divide any straggly mint and thyme plants.
- Plant or pot up basil seedlings.
Pests control in May
- Watch for aphids on broad beans and root flies on cabbages, carrots, and onions. Keep after weeds.
Feeding and watering in May
- Give side dressing of compost tea to half-grown plants.
- Keep all plants watered and well mulched.
Fruit tree to-dos in May
- Feed summer-fruiting plants with potassium sulfate to promote good flowering and fruit. Control weeds around the bush and cane fruit.
- Thin the fruit on apples, peaches, nectarines pears, and plums when they reach marble size. Thin heavy-cropping nectarines and peaches when the fruit is ½ in (1-1.5 cm) in diameter.
- Water new plantings deeply if the weather is dry. Water plentifully when fruit is swelling.
- Hang codling moth traps on apple trees.
- Spray against apple scab, mildew, and aphids.
- Prune wood damaged by fire blight.
- Remove any shoots on wall-trained fruits that are growing directly toward or away from the wall.
- Remove the blossoms from newly planted fruit trees to direct the plant’s energy into the production of strong new wood.
Berries to-dos in May
- Plant new strawberries and put cloches over strawberries if you want an early corp. Harvest strawberries as they ripen. Protect strawberry fruits with straw or black plastic sheeting.
- Keep new canes of blackberries and loganberries separate from the current year’s fruiting canes. Tie new canes of blackberries and hybrid berries to a system of support wires, allowing a maximum of eight canes per plant.
- Remove weak shoots from brambles. Thin our raspberry canes. Spray raspberries against raspberry beetles. Apply the first spray as soon as the first fruit turns pink.
- Summer-prune gooseberries by cutting back side-shoots to five leaves.
- Feed blackberry and hybrid berry plants with ammonium sulfate or other high-nitrogen fertilizer. Cover berries with netting to protect them from birds.
Citrus in May
- Plant citrus and tropical fruit this month. Feed citrus fruit with sulfate of ammonia; feed established trees with iron sulfate. Water citrus deeply in dry weather.
- Plant summer container plants when the danger of frost is past.
- Feed new transplants with liquid fertilizer and water as needed.
Regional Vegetable Gardening Tips for May:
These suggestions are divided into 4 major geographical areas: North and East and Midwest (zones 2 in the northernmost areas to 6 along the coast), the South (zones 7 in the north to 10 in the far south), the Southwest and California (zones 7 in the coolest areas to 11), and the Northeast (zones 5 in the highest elevations to 8 along the coast).
North and East and Midwest
- Early in the month: Rush to get these crops in if you haven’t planted
- Succession plantings of lettuce, beets, and carrots should be made from now until August, every 2 or 3 weeks, to provide a constant supply.
- Set out any time during the month, successive starts of cabbage, broccoli, and cauliflower plants for late-season harvest.
- Plants of tomatoes, eggplants, and peppers can go in the garden as soon as the danger of frost is past. Harden off warm-weather starts before setting them in the garden.
- Beans, corn, cucumbers, melons, potatoes, and squash may be planted in open ground in by mid-month, assuming the ground is not too cold. Sow bush beans 1 inch deep, 3 inches apart in rows 18 inches apart. Pole beans go into hills, 4 to 8 seeds to a hill; later thin to 2 or 3 plants.
- Plant tomatoes in well-fertilized soil and strong supports. Work in phosphate and potash rock; tomatoes require little nitrogen. Keep tomatoes well watered.
- Side dressings of complete fertilizer or aged compost will help along with all young seedling plants.
- If the season is mild, plant early corn. Add plenty of compost and a pound each of pulverized phosphate rock and potash rock to every 10 square feet of soil.
- Early thinning of plants in rows is important–overcrowding will lead to poor development. Thin bush beans, 4 inches apart; beets 3 inches apart; carrots, 2 inches apart; chard 6-8 inches; corn, 10-12 inches; lettuce 6-10 inches; New Zealand spinach, 12-18 inches; onions, 2-3 inches; peas, 2-3 inches; radishes, 2 inches; rutabagas, 4-5 inches; spinach, 3-4 inches; turnips, 3-4 inches. Replanting thinnings is rarely successful.
- Direct sow warm-weather crops: bush and pole lima beans, pole snap beans, cantaloupes, celery, collards, cucumbers, gourds, New Zealand spinach, okra, black-eyed peas, and crowder peas, pumpkins, rutabagas, squash, sunflower, turnips, and watermelon (if there is room). Sow a second planting of corn. Plant sweet potato slips, tomatoes, eggplants, collards, peanuts, and peppers. Plant cabbage for a fall crop.
- Plant seed of edible soybeans.
- Cut okra pods before they mature, so the plants will continue to bear all season. Plant in wide rows with stalks every 2 or 3 feet.
- Set out tomato plants. Plant 4 to 6 inches deep, water well, and shade for 3 days. Pinch out suckers that develop between the main stalk and the branches while they are quite small. Prune to 2 stems. This will prevent them from utilizing plant food and making too much foliage. Stake with 5-foot stakes.
- Stake tomatoes, eggplants, and peppers when about one foot high.
- Succession plantings: Set plants of eggplant, pimento, hot and sweet peppers where heads of cabbage, lettuce, mustard, and other cool-weather crops have been harvested.
Southwest and California
- Plant warm-weather crops now: bush and pole beans, lima beans, beets, cabbage, cantaloupes, casaba, cauliflower, celery, chard, sweet corn, Chinese and Armenian cucumbers, eggplants, gourds, leaf lettuce (in shade), lima beans, melons, New Zealand spinach, okra, peppers, pumpkins, radish, salsify, squash tomatoes. Train Chinese and Armenian cucumbers, pole beans, and tomatoes on stakes.
- Plant heat-loving vegetables in deeply composted holes: lima beans, summer squash, peppers, eggplant, and tomatoes.
- Tomatoes: a trellis-supported tomato will be more productive than one that sprawls on the ground. Set a trellis before the plant is in the ground for more than 3 weeks. Train each branch as it grows. Tie stems in loosely so as not to cut into the branch. Set tomatoes deeper in the garden than they were in the seedbed.
- Make successive plantings of vegetables every 10 days.
- Watercress can be planted in a shallow tub. Leaf lettuces can be planted in the shade.
- Plant summer cover crops of the drought-resistant legumes: tepary and black-eye beans.
- Mulch heavily with compost to help retain soil moisture and improve soil tilth.
- Irrigate thoroughly once a week. Gently dig around roots to see if plants have sufficient moisture. Water at the base of plants.
- Don’t work with beans or tomato vines when they are wet. Fungal diseases are easily spread in drops of water.
- All plants may be set out as soon as the last frost date has passed: cabbage, cauliflower, cucumbers, peppers, and tomatoes.
- Plant cabbage, cauliflowers, Brussels sprouts, and kale before mid-month.
- Direct seed pole and bush beans and midseason sweet corn. Sow pumpkin and squash toward the end of the month.
- Make successive plantings at 10-day intervals.
- Plant potatoes in well-drained, fertile soil.
- Thin plants that are already in the garden, and continue cultivation and weeding.
- Stop cutting asparagus after the middle of the month.