Gardener’s May To-Do List

Everything that needs to be done in the dirt this month, wherever you live.

May 1, 2015
Cherry blossoms

Here's your May gardening guide for all of North America's USDA Plant Hardiness Zones: 3-10. If you're not sure which zone you live in, check the map here to find out.

Zone 3

  • Remove winter protection from hybrid tea roses, but have those jute sacks ready in case of a freeze.
  • Begin hardening off annual flowers by exposing them to cooler temperatures for longer periods each day.
  • Seed cold-weather crops.
  • Give perennials and fruit trees a generous feeding of compost, and if it has been dry, water them deeply to boost their growth.
  • Toward the end of the month, plant potatoes and seeds of warm-season crops.
  • Protect cauliflower and broccoli transplants from root maggots with 4-by-4-inch collars made of heavy paper, placed on the soil around the base of the plants.

Zone 4

  • In the flowerbed, divide overgrown perennials, and establish new beds with the divisions.
  • Sow seeds of annual flowers such as bachelor's buttons, marigolds, and zinnias.
  • Start melon, cucumber, and squash seeds indoors or in a coldframe.
  • Plant frost-sensitive veggies—such as tomatoes, beans, and summer squash—at the end of the month.
  • Prune lilacs, azaleas, spirea, and other spring-flowering shrubs after they bloom.

Zone 5

  • After the soil has warmed to 60°F, transplant out tomatoes, peppers, eggplants, melons, cucumbers, and sweet potatoes.
  • Small, 3-foot-tall "tomato" cages work for peppers and eggplants; for tomatoes, use sturdier, 6-foot-tall rings made from 4-inch-square chicken wire.
  • Squeeze some last runs of cool-season crops into the garden; try some mâche (corn salad), a tasty cool-weather green.
  • Protect cucumbers, melons, and squash from pests by using row covers. (Be sure to remove them when plants blossom, though.)
  • Divide and replant summer and fall-blooming perennials.
  • Transplant evergreen shrubs and trees, and pop annual flowers into beds.

Zone 6

  • Plant out tomato transplants early in the month and those of peppers and eggplants by the end of the month.
  • Direct-seed squash, beans, corn, and okra.
  • Plant a few more runs of leafy greens.
  • Sow sunflowers, zinnias, marigolds. and cosmos wherever you need an extra splash of color.
  • Mulch roses with a 1-inch layer of compost.

Zone 7

  • Plant moonflower (Ipomoea alba), caladium, coleus, zinnia, and other heat-tolerant flowers.
  • Don't be too quick to give up on tender perennials and tubers, such as datura, Mexican bush sage (Salvia leucantha), cannas, and dahlias. You still may see new leaves by the end of the month.
  • Plant okra, tomatoes, eggplant, peppers, sweet potatoes, southern peas, and other heat-loving veggies.
  • Mulch peas and cole crops to keep the soil cool; water them regularly.
  • Thin peaches, plums, pears, and apples to about 6 inches apart.

Zone 8

  • Harvest spring crops daily to keep them producing for as long as possible.
  • Continue to plant heat-tolerant tomatoes, such as ‘Heatwave', ‘Sunchaser', and ‘Sweet 100'.
  • Plant eggplant, peppers, cucumbers, squash, okra, beans, sweet potatoes, melons, and southern peas this month.
  • Plant caladiums in shaded sites. Try narrow-leaved zinnia (Zinnia angustifolia) for hot spots. Give new plantings plenty of water.
  • Continue planting daisies, asters, coreopsis, marigolds, and sunflowers—they nourish the beneficial insects, which will help keep pests in check.
  • Check your drip irrigation system—you'll be depending on it soon.

Zone 9

  • Plant last runs of lettuce, choosing heat-tolerant varieties that are slow to go to seed.
  • Start new plantings of melons, squash, dried beans, okra, and southern peas that thrive in heat.
  • Set out heat-loving petunias, moss rose (Portulaca grandiflora), amaranth, vinca (Catharanthus roseus), nicotiana, marigolds, and sunflowers.
  • Pull out and compost primula, viola, calendula, and pansy plants that are no longer flowering well.
  • Use drip irrigation to provide a constant supply of moisture to beds; also mulch with organic materials, such as dried grass clippings, pine needles, or leaves.

Zone 10

  • Plant heat-loving veggies, such as sweet potatoes, okra, and southern peas.
  • Keep heat-tolerant herbs, such as lemongrass, going strong by feeding them with fish emulsion and seaweed spray.
  • If thyme, basil, and curry leaf show signs of mildew, spray them with a solution made from 1 tablespoon of baking soda and 1 gallon of water; repeat every few days.
  • Solarize empty garden beds: Cover them with clear plastic for a month or two to kill nematodes and weed seeds and pathogens in the soil.
  • Mulch all plants heavily.
  • Stop whiteflies and mealybugs with insecticidal soap.