March Gardening Tips for the Pacific Northwest

Winter's long wait is almost over. Get busy outdoors. As the weather starts to warm, it's time to dig in on planting, pruning, and pest control.


Divide Perennials

Early spring is the ideal time to divide crowded clumps of summer- and fall-blooming perennials. This includes purple coneflowers, Shasta daisies, asters, and garden mums. After planting divisions, don't forget to water if spring rains fail to materialize.

Learn how to divide perennials.

Begin Slug Patrol

As soon as bulbs begin to poke through soil, slugs start feeding. To get a jump on controlling these voracious chewers, put out slug bait when you see bulb shoots. Slugs are most active during mild, rainy weather. You'll likely spot three types of slugs.

European black slug: They are usually brown but occasionally black or white. This slug feeds on new growth and poses a large threat to garden plants.

Banana slug: Most often yellow or black-spotted yellow, banana slugs can also be green or white. They feed on mushrooms, leaf litter, and dead plants. As a result, they pose no threat to the garden.

Leopard slug: This slug is gray with black spots. It's omnivorous, eating garden plants but also feasting on insects, such as European black slugs.

Spray for Pests and Diseases

Break out the sprayer late this month to treat trees and shrubs typically attacked by scale. Spray horticultural oil, which also helps control mites. Don't spray blue spruce trees.

Learn more ways to fight garden pests.

Test Garden Tip: Awaken overwintered fuchsias by shifting them from darkness to a spot near a south-facing or other sunny window. Don't move the plants outdoors until all danger of frost has passed.

Start Planting

Wait to dig until after soil has warmed and isn't too wet. Watch maple trees to know when soil is warm enough for planting. When leaves start to emerge, soil should be good to go.

Edibles:

  • Get cole crops into the ground: broccoli, Brussels sprouts, cabbage, cauliflower, kale, and kohlrabi. Look for seedlings at local nurseries.
  • Tuck bare-root asparagus and rhubarb, as well as onion sets and potatoes, into soil.
  • Sow seeds of leafy salad favorites (lettuce, spinach) and onion-family plants (leeks, onions, shallots). Beets, carrots, and radishes can also be planted now.
  • Start warm-season seeds indoors so you'll have healthy seedlings for planting when all danger of frost has passed. This includes basil, eggplants, peppers, and tomatoes.

Get your tomatoes off to a good start.

Perennials:

  • Look for bare-root and potted perennials at garden centers. If you want to add early-spring perennials, such as creeping phlox, purchase plants while they're in bloom to ensure you're getting the color you want.
  • Nurseries have a great selection of bare-root plants. Buying bare-root plants is a great way to stretch your gardening dollars.
  • You can also plant potted or balled-and-burlapped landscape plants.

Test Garden Tip: Begin planting gladiola and begonia bulbs this month. If you're a big glad fan and want a season-long show, tuck bulbs into soil every two weeks until mid-July -- then sit back and enjoy the floral fireworks.

Prune Roses, Shrubs, and Clematis

Roses: Early in the month, remove old, thin, and unproductive rose canes. Cut back bush roses to 12-18 inches tall and shrub roses to 3 feet. Thin climbing roses if canes are thick and tangled.

Don't miss our tips for pruning roses.

Shrubs: Wait to prune spring-flowering shrubs after blossoms fade. It's OK to remove dead or storm-damaged branches prior to bloom; they may detract from the show.

Clematis: Along the coast, cut summer and fall bloomers back to the strongest stems. Scratch fertilizer into soil around the base of vines and water in. Refresh mulch around vines. Inland, wait to prune until all danger of a hard frost has passed. In all areas, prune spring-blooming clematis immediately after flowering.

Don't miss our BHG pruning guide.

Fertilize

Bulbs: As new shoots appear, scratch bulb fertilizer into soil around plants. This feeding ensures a strong show next year.

Landscape plants: Use a complete, all-purpose product for trees and shrubs. Apply before growth begins.

Rhododendrons, azaleas, and camellias: Choose a fertilizer designed for acid-loving plants.

Berries: Feed plants with an all-purpose fertilizer. You can also heap compost around canes. Do not feed strawberry plants until after harvest in June.

Test Garden Tip: Top-dress a rock garden using a mixture of sand, loam, and coconut fiber to reduce soil compaction and erosion, help soil retain moisture, and cool soil. This fast-draining topdressing also protects plant crowns from excess moisture. Don't worry how the garden looks after top-dressing. Rains will wash materials into soil.

Address Lawn Challenges

Bare spots: Repair bare spots in the lawn. Simply scratch up soil and toss on seed. Keep the seedbed moist until sprouts appear. If birds, rodents, or deer create heavy traffic in your yard, use clean straw or a light dressing of compost to protect seed from hungry critters.

Grass seed choices: If you're starting a new lawn, use fescue for shady areas and a mix of bentgrass and perennial ryegrass for sunny sections. Buffalograss thrives east of the Cascades. This drought-tolerant turf is a low-maintenance favorite in other regions where it's widely grown.

Weeds: Preemergent weed killers will take care of annual grassy weeds, such as crabgrass and annual bluegrass. The trick is applying it before seeds germinate. Usually, if you apply when forsythia begins to bloom, you'll hit the right window. Follow application instructions on the bag with regard to rainfall.

Check out our Weed Identification Guide.

Moss: For lawns that typically don't have a moss issue, choose a spring fertilizer that contains iron. The iron will eliminate any moss that invaded the lawn over winter.

Test Garden Tip: Fertilize lawns when grass starts to green up. Choose a complete fertilizer labeled for spring use.

Check out our lawn-fertilizer calculator.


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