April Gardening Tips
for the Willamette Valley

by Rod Smith
Oregon Certified Nursery Professional

© 2002-2017 Rodney A. Smith
All rights reserved.
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Planting

Summer Bulbs - Plant Gladiolus every two weeks until the first of July for a continuous bloom. Plant Callas, Ranunculus, Crocosmia and other summer bloomers anytime this month.

Vegetables - Beans, beets, broccoli, cabbage, carrots, onions, peas, potatoes and radishes can be planted just before the last frost. Interplanting onions helps to prevent cutworms. Corn requires a soil temperature of at least 60 degrees. Start cucumbers, melons, peppers, squash and tomatoes indoors for May planting.

Annuals & Perennials - Many perennials and groundcovers bloom in April. Buying a few in bloom each month insures continuous flowers in your landscape. Annual seeds of Asters, Cosmos, Marigolds, Zinnias and Snapdragons may be sown now. Started annuals may be set out now, but protect them from frost.

Spring Bulbs Care

Remove the spent flowers after they finish blooming so they will not use up energy producing seeds. Do not cut off the leaves because they are needed to store up food for next spring's flowers. Remove the leaves when they turn yellow and start to dry.

Lawn Care

Lawns need a complete fertilizer every six weeks through September. A weed & feed formula can be used to control broadleaf weeds, but it has to be applied evenly to the entire lawn. A liquid weed killer works better to kill clover and only needs to be applied where there are weeds.

Check for thatch, which is a layer of dead roots and stems on top of the soil. An inch thick layer of thatch causes problems with watering, fertilizing and disease. Remove it with a power rake or thatcher and reseed.

If the lawn is full of weeds or coarse grass, April and May are good months to kill every thing with Roundup, power rake, and re-seed with a good blend of fescue and perennial ryegrass.

Pests

Watch for areas of lawn that are thinning or yellowing in an otherwise healthy lawn. It might be caused by European Crane Fly. To check, drench a square foot of soil with warm, soapy water. If half inch long, gray brown larvae appear, treat the lawn with beneficial nematodes or Imidacloprid.

Watch for adult crane flies. They are Common Crane Flies, which are new in the Northwest and much more destructive that European Crane Fly, because they feed on the lawn in July and August when the lawn is stressed by dry weather.

Leaf spot diseases are worst when leaves are young and tender, and the weather is cloudy and rainy. Begin spraying fruit trees, dogwoods and roses every seven to ten days with a fungicide. Include an insecticide when insects are present. Do not spray insecticides on open flowers because it kills the bees which we need. For codling moth on apples, spray just as the flowers are about to open and again when the petals have mostly fallen.

Watch for sooty mold on camellias and other broadleaf evergreens. Spray with oil to control scale insects and the sooty mold will go away.

Check rhododendrons and azaleas for tiny, light brown spots on the underside of the leaves caused by lace bugs. Severely damaged leaves are almost white. Spray with a product containing Imidacloprid, such as, Bayer Advanced Garden Tree and Shrub Insect Control, or Spinosad, such as Captain Jack’s Dead Bug Brew, to prevent lace bug damage. Both are toxic to bees, so do not use if flowers are about to open or until flowers have dropped off.

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