Rainline Garden

When to plant dahlias in Tri-Cities (Pasco, Kennewick, Richland), WA

Plant dahlia tubers in Tri-Cities (Pasco, Kennewick, Richland) May 1–29.

Moderate Plant tubers

Why these dates

Tri-Cities (Pasco, Kennewick, Richland)'s typical last spring frost is April 27. Frost kills dahlias, so planting starts once frost risk drops, around May 1. Keep row cover or a frost blanket handy for the first couple of weeks, since a late frost is still possible.

Columbia Basin and low eastern valleys. Hot, dry summers and quick spring warm-up. Warm crops go in earlier than west of the Cascades, and irrigation matters more than rain.

Difficulty
Moderate
Sun
Full sun
Spacing
18 to 24 inches apart
Planting depth
4 to 6 inches deep, eye pointing up
Frost
Killed by frost
Flowers
Blooms from midsummer until the first frost

Step by step

  1. Pick a sunny spot with soil that drains well, and mix in an inch or two of compost.
  2. Plant dahlia tubers May 1–29, 18 to 24 inches apart. 4 to 6 inches deep, eye pointing up.
  3. Don't water tubers until shoots appear, then water deeply once a week. Stake tall varieties when you plant so you don't spear the tuber later.
  4. Harvest: Cut flowers when they're almost fully open, early in the morning. The more you cut, the more they bloom.

Varieties that do well here

  • Café au Lait
  • Bishop of Llandaff
  • Cornel Brons

Watch out for

Slugs and earwigs chew young shoots and petals. Use iron phosphate slug bait early in the season.

Tubers rot in cold, wet soil, so wait until it warms. West of the Cascades many gardeners leave them in the ground over winter under thick mulch; east of the mountains, dig and store them after the first frost.

Common questions

When is the last frost in Tri-Cities (Pasco, Kennewick, Richland), WA?

Typically April 27. In 9 years out of 10, frost is over by May 10. These are 1991–2020 NOAA climate normals for Pasco Tri-Cities Airport.

Is it too late to plant dahlias in Tri-Cities (Pasco, Kennewick, Richland)?

The spring planting window runs through May 29. Later plantings may not have time to bloom well before the first fall frost, which usually arrives around October 11.

When do dahlias bloom?

Blooms from midsummer until the first frost. Cut flowers when they're almost fully open, early in the morning. The more you cut, the more they bloom.

Also plant in Tri-Cities (Pasco, Kennewick, Richland) around the same time

Planting dates for dahlias in nearby areas

Full planting calendar for Tri-Cities (Pasco, Kennewick, Richland) · Dahlias in every city