Marin Master Gardeners
University of California
Marin Master Gardeners

Gardener's checklist for spring

What to do in your garden in the spring

APRIL

  • Troubleshoot your irrigation system for missing or clogged emitters and broken spray heads.
  • Fertilize spring bulbs after bloom. Remove dead flowers but not the leaves until they wither.
  • Check often for aphids on tender new plant growth. Remove infestations with a hard spray of water or insecticidal soap.
  • Handpick snails and slugs after dark or apply a pet-friendly bait.
  • Be diligent about pulling weeds before they set seed.
  • Mulch around new plants to suppress weeds and retain moisture. Renew mulch around existing plantings. Keep mulch clear of stems and trunks.
  • Weather permitting, move frost-tender seedlings and plants outdoors. Harden off transplants before planting by gradually exposing them to outdoor conditions.
  • Sow seeds of summer and fall-blooming annual flowers directly in the ground. Cosmos, bachelor buttons, sunflowers, nasturtiums and zinnias are easy to grow from seed. Keep the seed bed moist.
  • Plant summer bulbs, corms and tubers, such as callas, cannas, dahlias, gladiolus and tuberous begonias.
  • Sow seeds of beets, carrots, lettuce and Swiss chard. Plant potato tubers.
  • Thin raspberry canes.
  • Thin developing fruit such as apples when they reach dime size.
  • Feed lawn areas with a slow-release fertilizer.
  • Fertilize citrus.
  • Apply chelated iron to azaleas, camellias and gardenias if leaves are yellowing between the veins.
  • Renew container plants by adding a slow-release fertilizer or repotting in fresh soil.
  • Clean winter debris from ponds, fountains and bird baths.

MAY

  • Monitor and control snails, slugs and aphids.
  • Prune spring-flowering shrubs are they have finished flowering.
  • Pinch back chrysanthemums and annual flowering plants to encourage branching and compact growth.
  • Cut off spent flowers for continued bloom.
  • Prune azaleas, camellias and rhododendrons after they have finished blooming. Feed with a balanced fertilizer formulated for acid-loving plants monthly during the spring and summer.
  • For modern roses, as new growth develops, remove any canes that are growing inward to aid in air circulation. For old garden roses that bloom only once, do the major prune after the bloom cycle is complete. Pick up diseased leaves.
  • Continue to plant seeds of summer and fall-blooming annual flowers or buy cell packs at nurseries.
  • Sow seeds of beans, beets, carrots, corn (early varieties), cucumbers, lettuce, melons, pumpkins, Swiss chard and summer and winter squash.
  • Transplant starts of eggplants, peppers and tomatoes.
  • Plant an herb garden in containers or in a bed near your kitchen. Keep mint in its own pot to control its rampant spread.
  • Fertilize citrus.
  • Continue to thin developing fruit.
  • Repot cymbidiums if they have outgrown their containers or if the planting medium has broken down.
  • Cut roses to bring indoors. As you cut, plunge the stems immediately into a bucket of water.

JUNE

  • Check soil moisture and adjust the watering schedule on your irrigation controller accordingly. Water early in the day. Watch container plants, which may need daily watering.
  • Control powdery mildew, a fungus that likes dry summer conditions. Spray susceptible plants with a horticultural oil or biological fungicide.
  • Cut off spent flowers for continued bloom.
  • Promote another bloom cycle of early-blooming perennials like Shasta daisies (Leucanthemum) and catmint (Nepeta) by cutting back spent stems or shearing old growth.
  • Fertilize roses and other summer-blooming plants. Use little or no fertilizer on herbs.
  • Sow seeds of basil, beans, beets, carrots, corn (early varieties), cucumbers, lettuce, summer and winter squash.
  • Transplant starts of broccoli, Brussels sprouts, eggplant, peppers and tomatoes.
  • Make compost tea for a mild liquid fertilizer.
  • Stake tall plants such as dahlias, gladiolus and lilies as needed.
  • Provide support for the vining stems of indeterminate tomato plants. Feed with a low-nitrogen fertilizer when fruit starts to develop. Do not overwater.
  • Protect fruit crops from birds with plastic bird netting or fabric row covers.
  • Use pot feet or boards to elevate containers sitting on hot pavement.
  • Clear dry brush and grasses to create a 30-foot fire-safe space around your home.
  • Harvest blooming lavender to dry for indoor use.

Contributors:
Faith Brown, Marie Narlock, UCCE Marin County Master Gardeners

Resource:
Northern California Gardening: A Month-by-Month Guide by Katherine Grace Endicott

Webmaster Email: banielsen@ucanr.edu