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May Gardening Tips

Garden Maintenance

  • Set out traps for earwigs, slugs, and whitefly.
  • Thin pit fruits at or before pit hardening.
  • Thin apples when ½” diameter.
  • Mow grass or cultivate soil around orchard to discourage thrips and plant bugs.
  • Mulch around plants to control weeds and conserve moisture. Be sure to leave a small circle of bare soil around the base of each plant.
  • Deep water trees and shrubs. Build water basins, but do not allow water to stand against the trunks.
  • Prepare dahlia bed with rich soil.
  • For continued bloom, cut off spent flowers.
  • Hang strips of foil or CD’s in fruit trees to help deter birds.
  • As spring=flowering shrubs finish blooming, prune to shape, removing old and dead wood.
  • Trim hedges; lightly trim azaleas, fuchsias, bushier plants.
  • Thoroughly clean debris from ponds, fountains and bird baths.
  • Check dates of Master Gardener classes.


  • Strawberries (end of May).
  • Kiwi, ? recommended NPK.
  • Young fruit trees, if missed in April.
  • Cane berries after harvest.
  • Rhododendron after bloom.
  • Cool season turf grass.
  • Roses at bloom start.
  • Citrus
  • Corn – N when knee high.
  • If you did not use slow release fertilizer for summer bloomers. Give then a feeding now.
  • Fertilize vegetables monthly.
  • Feed indoor plants with slow release fertilizer.

Spray: Check the California Backyard Orchard website for current information.

  • Apples and pears for codling moth: first treatment when pears are ½” in diameter and apples are ?”. For timing use codling moth traps or call Master Gardeners at (530) 621-5512.
  • For codling moth control, attach 4” corrugated cardboard bands around tree trunks in early May; in late May or early June remove and destroy bands to kill the larvae and pupae found in the cardboard.
  • Check for citrus scale and control with horticultural oil. Encourage natural enemies and protect trees from ants.
  • Continue application of sulfur or other fungicide to grapes if damp weather persists.
  • If needed, apply Tanglefoot around tree trunks to deter ants and other crawling insects.
  • Pears, except Comice – weak copper spray when in bloom, one to three applications for fire blight.
  • Check roses for black spot, mildew and rust and spray if needed
  • Check roses for aphids; control with a strong spray of water or insecticidal soap.

Note: all the effective insecticidal sprays kill bees and other beneficial. Do not spray while trees are in bloom.

What To Plant In May

Plant Seed

  • Beans, beets, carrots, corn, cucumber, melons, okra, parsley, parsnip, peppers, pumpkins, radish, all squash, tomatoes.
  • Annuals
  • Cannas, lilies, tuberous begonias.

Plant Seed - Greenhouse or Cold Frame

  • Time for house cleaning.

Set out Plants

  • Eggplant, herbs, parsley, peppers, tomatoes, all vine crops.


  • Marigolds, zinnias, snapdragons, sunflowers, hollyhock, dahlias, lobelia, salvia, cosmos.


  • Transplant tomatoes, eggplant and peppers as temperatures warm.
  • At cooler elevations, transplant lettuce cabbage family, collards and kale.
  • Plant cilantro and two week intervals for a steady supply.


Cottage Garden photo credit P. Atkins

photo by P. Atkins, used with permission