Spring flowers like sweet peas will spill over into the garden this month. The roses will have heady days in May and the time for warm-weather vegetables like beans and peppers and tomatoes is very close.
Warm-weather vegetable starts can be transplanted into the kitchen garden probably by mid month and direct sowing of seeds will not be far behind once the soil has warmed. Beans will do best after the soil has reached 55ºF (13ºC) and corn will take off after the soil has reached 65ºF (18ºC).
You can minimize transplant shock if you hold off putting melons and summer and winter squash seedlings in the garden until a week or so after the last frost. Peppers and eggplants can be transplanted into the garden two or three weeks after the last frost.
Herbs starts like dill, Green oregano, sweet marjoram, cilantro, rosemary, sage, summer and winter thyme, and garlic chives can be transplanted into the garden this month. You might want to wait just a bit longer before planting basil and lemon grass.
Here is a kitchen garden guide for warm regions—growing zones 7-11—for the month of May.
Unsettled weather. Continue to sow early summer crops in the coldframe or greenhouse or beneath cloches if the weather in your region has not yet settled. Few seeds will germinate if the soil temperature is below 45ºF (7ºC) and warm-weather crops are not going to thrive until the night temperatures stay consistently above 50ºF (10ºC). If temperatures could dip, use horticultural fleece or cloches in the garden for early warm-weather corps.
Greenhouse and coldframe. Sow tender vegetables such as outdoor 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.
In the garden. Start sowing vegetables without protection if the soil and night time 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 of early or start introducing summer crops.
Early month sowing. 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. Remove cloches from broad beans, carrots, and peas.
Mid-month sowing. Sow seeds of beans, corn, okra, squash, cucumber, cantaloupe, and other tender vegetables and herbs after temperatures have reached the 70s. Or if you have started these indoors, set out transplants after mid-month: tomato, eggplant, pepper, and sweet potato. Sow Chinese cabbage. Pinch out the tips on broad beans to encourage good pod set and to deter attack from aphids.
Harvest early crops. 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.
Successive plantings. 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 transplants. 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.
Herbs. Plant or pot up basil seedlings. Take cuttings of pot marjoram, rosemary, sage, and thyme. Divide any straggly mint and thyme plants.
Pests. Watch for aphids on broad beans and root flies on cabbages, carrots and onions. Keep after weeds.
Feeding and watering. Give side dressing of compost tea to half-grown plants. Keep all plants watered and well mulched.
Fruit trees. Feed summer-fruiting plants with potassium sulfate to promote good flowering and fruit. Control weeds around 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 fruit is ½ in (1-1.5 cm) in diameter. Water new plantings deeply if weather is dry. Water plentifully when fruit is swelling.
Hang coddling moth traps on apple trees. Spray against apple scab, mildew, and aphids. Watch for pests and signs of disease. Trap larvae on trunks of trees and destroy. 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 plants energy into the production of strong new wood.
Berries. 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. 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.
Containers. Plant summer container plants when the danger of frost is past. Feed new transplants with liquid fertilizer and water as needed.