Oregon · Washington · Idaho
When to plant dahlias
Plant in the garden: Portland and Seattle May 15 – Jun 12; Spokane May 20 – Jun 17; Boise May 1–29; Bend Jun 9 – Jul 7.
Your dates in
Dahlias are tender perennials from the mountains of Mexico and Central America that grow from tubers, a clump of fleshy roots that sends up new stems each year. They are grown mainly as cut flowers, with blooms from small pompons to dinnerplate types wider than your hand, in nearly every color except true blue. The dahlia has been Seattle's official city flower since 1913.
Puts dahlias on your free plan, with dates for your town and a spot in your beds.
- 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
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.
Dahlia planting dates
| Towns | Plant in the garden |
|---|---|
| Portland, OR, Seattle and Tacoma, WA | May 15 – Jun 12 |
| Spokane, WA, Astoria, OR | May 20 – Jun 17 |
| Boise and Meridian, ID | May 1–29 |
| Bend and Redmond, OR | Jun 9 – Jul 7 |
Dates for six main cities. For any of the other 80 towns, type it in the box at the top of the page or browse all towns.
| Gresham, OR, Hillsboro and Beaverton, OR, Oregon City and West Linn, OR, Portland, OR, St. Helens and Scappoose, OR, Wilsonville and Canby, OR | May 15 – Jun 12 |
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| Corvallis and Albany, OR, Cottage Grove, OR, Eugene, OR, McMinnville and Newberg, OR, Salem, OR | May 15 – Jun 12 |
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| Ashland and Talent, OR, Grants Pass, OR, Medford, OR, Roseburg, OR | May 15 – Jun 12 |
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| Astoria, OR, Brookings and Gold Beach, OR, Coos Bay and North Bend, OR, Newport and Lincoln City, OR, Tillamook, OR | May 20 – Jun 17 |
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| Bend and Redmond, OR, Klamath Falls, OR | Jun 9 – Jul 7 |
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| Burns, OR | Jun 11 – Jul 9 |
| Lakeview, OR | Jun 4 – Jul 2 |
| Madras, OR | May 25 – Jun 22 |
| Prineville, OR | Jun 1–29 |
| Baker City, OR, Enterprise and Joseph, OR | May 25 – Jun 22 |
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| Hermiston, OR, Hood River, OR, Ontario, OR, Pendleton, OR, The Dalles, OR | May 1–29 |
| John Day, OR | May 28 – Jun 25 |
| La Grande, OR | May 20 – Jun 17 |
| Bremerton and Port Orchard, WA, Everett, WA, Kent, Renton and Auburn, WA, Olympia, WA, Seattle and Tacoma, WA, Shelton, WA | May 15 – Jun 12 |
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| Anacortes, WA, Bellingham, WA, Friday Harbor and the San Juans, WA, Mount Vernon and Burlington, WA, Oak Harbor and Whidbey Island, WA | May 15 – Jun 12 |
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| Aberdeen and Hoquiam, WA, Forks, WA, Long Beach and Ilwaco, WA | May 20 – Jun 17 |
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| Port Angeles, WA, Port Townsend, WA, Sequim, WA | May 15 – Jun 12 |
| Centralia and Chehalis, WA, Longview and Kelso, WA, Vancouver, WA | May 15 – Jun 12 |
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| Chelan, WA, Wenatchee, WA | May 1–29 |
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| Leavenworth, WA, Omak and Okanogan, WA, Winthrop and Twisp, WA | May 20 – Jun 17 |
| Ellensburg, WA, Goldendale, WA | May 20 – Jun 17 |
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| Ephrata and Quincy, WA, Moses Lake, WA, Sunnyside, Grandview and Prosser, WA, Tri-Cities (Pasco, Kennewick, Richland), WA, Walla Walla, WA | May 1–29 |
| Yakima, WA | May 8 – Jun 5 |
| Colville, WA, Pullman, WA, Spokane, WA | May 20 – Jun 17 |
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| Bonners Ferry, ID, Coeur d'Alene and Post Falls, ID, Sandpoint, ID | May 20 – Jun 17 |
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| Lewiston, ID | May 1–29 |
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| Moscow, ID | May 20 – Jun 17 |
| Boise and Meridian, ID, Emmett, ID, Nampa and Caldwell, ID | May 1–29 |
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| McCall, ID | Jun 22 – Jul 20 |
| Burley and Rupert, ID, Idaho Falls, ID, Pocatello, ID, Rexburg, ID, Twin Falls, ID | May 20 – Jun 17 |
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| Salmon, ID | May 25 – Jun 22 |
Dahlia year at a glance
| Task | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | May | Jun | ||||||||||
| Cut flowers | Jul | Aug | Sep | Oct |
Around Portland. Colder towns, especially east of the Cascades, run a few weeks later; the table above has your town's planting dates.
How to grow dahlias
- Pick a sunny spot with soil that drains well, and mix in an inch or two of compost.
- Plant dahlia tubers on your city's dates, 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.
Growing dahlias in your part of the Northwest
The same plant behaves differently on the wet west side, the foggy coast and the dry, colder east side.
West-side valleys
Willamette Valley, Puget Sound, southern Oregon
Many Portland and Seattle gardeners leave dahlia tubers in the ground with a thick mulch, but tubers often rot in wet clay. Lifting them in fall is safer in heavy soil. Slugs and earwigs chew new shoots.
Coast
Oregon and Washington coast
Dahlias bloom well in cool coastal summers. Stake them firmly against wind.
East of the Cascades
Columbia Basin, Yakima, Boise, Spokane, north Idaho
Dig tubers after the first frost and store them indoors, since the ground freezes too deep for them to survive. Spider mites and hot afternoon sun can stress plants; water deeply.
High desert and mountain towns
Central Oregon, high eastern Oregon valleys, McCall, Salmon
Plant after frost danger passes and dig tubers in fall. The short season means fewer blooms before frost, so start tubers in pots indoors in April.
More dahlia varieties
More widely sold picks that do well somewhere in the Northwest. The tag says which part of the Northwest suits each one best.
Café au Lait
Huge, soft cream to blush-pink blooms that are a wedding and cut-flower favorite. Tall plants need sturdy staking and protection from wind.
Both sides
Bishop of Llandaff
Bright scarlet single flowers over nearly black foliage. It doesn't need staking as much as big dahlias and is loved by bees and other pollinators.
Both sides
Cornel Brons
Tidy, rounded bronze-orange ball blooms on long stems. Very productive and long lasting in a vase, it is a florist favorite.
Both sides
Kelvin Floodlight
Enormous clear yellow blooms on tall, strong plants. It makes a big impact in a border and lasts well as a cut flower.
Both sides
Thomas Edison
Large, rich royal purple blooms on tall plants. A long-time favorite that is easy to find, productive and good for cutting.
Both sides
Wizard of Oz
Small, perfectly rounded blush-pink ball blooms on long stems. Prolific and great in bouquets, it suits gardeners who want lots of smaller flowers.
Both sides
How much to grow
How many to plant
For a cutting bed, 6 to 12 tubers give flowers for the house every week from July to frost.
In the vase
Cut dahlias last about four to six days in the vase. Recut stems and change the water often.
Key numbers
- 60°FPlant when soil is
- Once shoots appearFirst water
- 3–4 leaf pairsPinch at
- Low nitrogenFertilizer
- 40–50°FStore tubers
- DieFrozen tubers
Top care tip: Feed with a low-nitrogen fertilizer and cut flowers often, since more cutting means more blooms.
The plant science
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.
Good neighbors
Good neighbors
- Zinnias and cosmos. Same planting date and sunny needs; a mixed cutting bed.
Pests and problems
What most often goes wrong with dahlias in Northwest gardens, how to spot it and what to do.
Slugs and earwigs
Signs: Chewed shoots in spring and ragged petals in summer.
What to do: Slug bait early, and rolled-up newspaper traps for earwigs.
Powdery mildew
Signs: White coating on leaves in late summer.
What to do: Space for airflow and water at the base.
Tuber rot
Signs: Tubers turn mushy in winter.
What to do: Dig and store tubers in damp peat or wood shavings where winters are wet or cold.
Common questions about growing dahlias
When should I plant dahlias in Oregon, Washington and Idaho?
Plant in the garden: May 15 – Jun 12 in Portland and Seattle, May 20 – Jun 17 in Spokane, May 1–29 in Boise and Jun 9 – Jul 7 in Bend. Pick your town at the top of the page for your own dates.
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.
See what else to plant in May or June.
Sunflowers
Zinnias
Sweet peas
Tulips
Daffodils
Peonies
Cosmos
Nasturtiums
Marigolds
Calendula
Snapdragons
Ranunculus