When to plant dahlias in Brookings and Gold Beach, OR

Plant dahlia tubers in Brookings and Gold Beach May 20 – Jun 17.

Moderate Plant tubers

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

Why these dates

Brookings and Gold Beach's typical last spring frost is January 31. Frost kills dahlias, and warm-season crops also need warm soil. Soil here stays cold for weeks after the last frost, so planting waits until about May 20.

Coast. Mild winters but cool, foggy summers. Frost is rarely the problem; warmth is. Pick early, cool-tolerant varieties of tomatoes and squash.

How to grow dahlias in Brookings and Gold Beach

Pick a sunny spot with soil that drains well, and mix in an inch or two of compost.
Plant dahlia tubers May 20 – Jun 17, 18 to 24 inches apart. 4 to 6 inches deep, eye pointing up.
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.
Harvest: Cut flowers when they're almost fully open, early in the morning. The more you cut, the more they bloom.

Key numbers

60°FPlant when soil is
Once shoots appearFirst water
3–4 leaf pairsPinch at
Low nitrogenFertilizer
40–50°FStore tubers
DieFrozen tubers

How it works

The plant biology behind the advice above, in plain language.

What you're planting

Dahlias grow from tuberous roots, native to the highlands of Mexico. New shoots come only from the crown, the old stem where the tubers attach, so a tuber with no piece of crown and no eye will never sprout. Look for firm tubers with a visible eye or a bit of crown tissue.

Warm soil and dry feet

Tubers rot in cold, wet soil, so plant once the soil has warmed to about 60°F, usually late April or May in the Northwest. Don't water after planting until shoots appear; the tuber has all the moisture it needs, and extra water just invites rot. Once plants are growing, water deeply about once a week.

Pinching for more flowers

When a young plant has three or four pairs of leaves, pinch out the central growing tip. The plant then branches into several stems, giving more flowers on longer stems. Deadhead regularly: spent blooms are cone-shaped and pointed, while buds are round. Removing spent flowers keeps the plant from setting seed, so it keeps blooming until frost.

Feeding

Use a fertilizer that's low in nitrogen and higher in phosphorus and potassium. Too much nitrogen grows lush leaves, weak stems, fewer flowers, and tubers that store poorly over winter.

Winter: dig or leave?

Frozen tubers die. West of the Cascades, dahlias in well-drained soil often survive winter in the ground under a thick layer of mulch. In heavy, wet clay or in colder areas, dig them after frost blackens the leaves. Let the clumps dry a few days, then store them at 40 to 50°F in barely damp wood shavings, peat or vermiculite. Check them monthly for rot or shriveling.

Pests and problems

Slugs and earwigs chew young shoots and petals. Powdery mildew shows up late in the season. Plants with mottled, streaked or crinkled leaves and stunted growth may have a virus. There's no cure, so discard them to keep it from spreading. Dahlias grown from seed don't come true, which is why named varieties are sold as tubers.

Common questions

When is the last frost in Brookings and Gold Beach, OR?

Typically January 31. In 9 years out of 10, frost is over by March 21. These are 1991–2020 NOAA climate normals for Brookings.

Is it too late to plant dahlias in Brookings and Gold Beach?

The spring planting window runs through June 17. Later plantings may not have time to bloom well before the first fall frost, which usually arrives around December 27.

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.

Do I have to dig up dahlias every fall?

Not always. West of the Cascades, dahlias in well-drained soil often survive under a thick mulch. In heavy, wet clay or colder areas, dig them after the first frost and store them at 40 to 50°F.

Why aren't my dahlia tubers sprouting?

Either the tuber has no eye or piece of crown, or it rotted in cold, wet soil. Plant firm tubers with a visible eye once the soil reaches about 60°F, and don't water until shoots appear.

Why are my dahlias blooming so late?

Tubers planted in cold soil grow slowly, and plants given too much nitrogen put on leaves first. Start tubers in pots indoors in April to get ahead, and use a low-nitrogen fertilizer.

Also plant in Brookings and Gold Beach around the same time

Planting dates for dahlias in nearby areas

Astoria, OR May 20 – Jun 17
Coos Bay and North Bend, OR May 20 – Jun 17
Tillamook, OR May 20 – Jun 17
Newport and Lincoln City, OR May 20 – Jun 17
Aberdeen and Hoquiam, WA May 20 – Jun 17
Forks, WA May 20 – Jun 17

Full planting calendar for Brookings and Gold Beach · Dahlias in every city