Here’s what to plant now, and what has to wait because of the Northwest’s cold spring
The second week of May is still too early to set out heat-loving vegetable starts such as tomatoes, peppers and squash unless you have a protected area close to a building or a night-time covering such as agricultural fleece to protect the young plants from cold nights.
Anything less than 50 degrees is going to send shivers up the stem of a tomato plant. Sometimes they even turn blue or purple from the cold.
But this is a good week to add perennial plants, rhododendrons and other spring flowering shrubs, and also to prune lilacs that have finished flowering. You also can continue to plant seeds of lettuce, kale and other leafy crops in the ground. If you have warm soil in raised beds then beans and pumpkins seeds can go into the ground too.
Q. Can I plant a lawn of Kentucky bluegrass in our area? I live in Olympia. Also when is it warm enough to seed a new lawn? — G.P., Olympia
A. Nope. Kentucky bluegrass does fine in Eastern Washington but not here. Other grass seeds to avoid are zoysia and Bermuda grass, but these warm-season grasses are rarely sold in our area. In Western Washington look for a grass seed mix of perennial rye grasses and red or chewing fescues.
Grass seed sprouts best when soil temperature is above 50 degrees and the air is cool and moist. In Western Washington, that is usually the months of April and May.
When you look for grass seed, chose the more expensive blend with named varieties. The extra price most likely means the grasses are new and improved and the added expense is because a royalty is being paid to the university that introduced the seed. The newest grass seed varieties are more drought resistant and slower growing so you will mow and water less.
When it comes to grass seed, the more you know the less you’ll mow.
Q. I was given some dahlia tubers. When do I plant them and how deep should they be planted? — B.H., Sumner
A. The middle of May is a good time to plant dahlias. The size of the dahlia determines how deep to plant.
The huge dinner-plate size bloomers grow on stalks that can be 7 to 8 feet high. They should be planted 8 inches deep. Be sure to add a stake or post at planting time as the taller dahlias will need to be staked upright.
The smaller dahlias may not need staking and these can be planted 3-4 inches deep. If you have a some mystery varieties, try to plant the largest tubers (bigger than your fist) at least 6 inches deep and smaller tubers more shallow.
Slugs love dahlias so be ready with the slug bait at the first sign of new growth pushing up from the ground.
Q. I would like to grow plants in a window box. I was inspired by you planting a window box at your home that I found on YouTube. Problem is, your demo was using begonias and lobelia for a shaded area. I want flowers that will grow in hot sun as my window box will be on the west side of the house. What flowers do you suggest? — G., email
A. The classic choice for a sunny window box or a hanging basket in the sun are the ivy geraniums or Pelargonium peltatum. Look for ivy geraniums in the Cascade series as they come in many colors and have been bred for maximum flowers on trailing plants that have a distinctive ivy-shaped leaf.
Some more flowers that like it hot include the fan flower, or Scaevola, with more succulent leaves and blue or white blooms and the many types of petunia. Look for improved petunia varieties such as the Supertunia varieties that are better able to handle our sometimes rainy summer weather.
One more tip for your window box: If you plan on leaving your windows open to catch a summer breeze, then go with the ivy geraniums. They have a slight fragrance that repels flies and mosquitoes.
Marianne Binetti has a degree in horticulture from Washington State University and is the author of several books. Reach her at binettigarden.com.
Upcoming gardening classes
Want to learn Container Gardening Do’s and Don’ts? Join Marianne Binetti on Saturday, May 14, at the Peninsula Home and Garden Show from 2:30 to 4 p.m. at the Kitsap County Fairgrounds Events Center in Bremerton.
Learn about how to grow “The Heavenly H Plants: Hydrangeas, Hellebores and Heucheras” at the Grays Harbor and Pacific County Home & Garden Show on Sunday, May 15. Marianne Binetti will be speaking from noon to 1 p.m. at the Grays Harbor County Fairgrounds in Elma.
This story was originally published May 7, 2022 at 5:00 AM.