How to Plant, Grow, and Care for Dahlias
Dahlias are breathtakingly gorgeous flowers that come in every color of the rainbow. The tubers are planted in late spring, and the flowers will bloom continuously from midsummer through fall. Learn more about planting, growing, and caring for dazzling dahlias in our Dahlia gardening guide.
About Dahlia Flowers
Picking a favorite dahlia is like going through a button box! The flowers can range in size from petite 2-inch lollipop-style pompoms to giant 15-inch “dinner plates.” Most varieties grow 4 to 5 feet tall. Dahlias grow in a wide range of beautiful colors, including white, yellow, orange, pink, dark pink, red, dark red, lavender, purple and black, light blend, bronze, flame, dark blend, variegated and bicolor!
Dahlia is a genus of tuberous plants that are members of the Asteraceae family. The tubers are planted in the ground in late spring (around the month of May) and generally flower from July to the first autumn frosts. Dahlias are perfect for a border garden and make lovely cut flowers. Growing vegetables? Put a row of dahlias on the border, where they will not shade your edibles.
Are Dahlias Perennials or Annuals?
Dahlias are tender perennials in their native warm climate of Mexico. In the U.S., they are considered a perennial in hardiness zones 8 and higher. See the USDA hardiness zone page.
However, in colder regions (zones 7 and lower), dahlias are treated as annuals. That said, some gardeners have had luck keeping the dahlias in the ground in zones 6 and 7.
Luckily, cold-weather gardeners can also just dig up the tubers after the first fall frost and store them in their garage until spring. Learn how to dig up dahlias in the guide below.
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Dahlias thrive in 6 to 8 hours of direct sun, especially morning sunlight, and they benefit from protection from wind. Consider their size at maturity when planting. They grow best in rich, well-draining soil with a pH of 6.0 to 7.5. Amend heavy clay soil with aged manure or compost to lighten and loosen the soil texture for better drainage.
When to Plant Dahlias
- Dahlias will not tolerate cold soil. Plant when the soil reaches 60ºF (15°C) and any danger of frost has passed.
- Planting dahlias a few days after tomatoes are planted in the ground is a good rule of thumb.
- Some gardeners start tubers indoors in containers a month ahead to get a jump on the season. Medium to dwarf-size dahlias will do well in containers.
How to Plant Dahlias
Avoid planting dahlia tubers that appear wrinkled or rotten. Pink “eyes” (buds) or a little green growth are good signs.
- Plant large dahlias and those grown solely as cut flowers in a dedicated plot where they will be free from competition from other plants. Set tubers in rows spaced 3 feet apart. If you plant dahlias about 1 foot apart, they make an excellent flowering hedge and will support each other.
- Plant medium- to low-height dahlias, usually in the 3-foot tall range, among other summer flowers. Set them 2 feet apart.
- Plant the smallest bedding dahlias, grown from seed, 9 to 12 inches apart.
Start by digging a 6- to 8-inch deep hole to plant the tubers. It also helps to mix some compost and a handful of bonemeal into the planting hole. Otherwise, do not fertilize at planting.
- Set a tuber into the hole with the growing points, or “eyes,” facing up.
- Do not break or cut individual dahlia tubers (as you would with potatoes).
- Cover the tuber with 2 to 3 inches of soil. (Some say 1 inch is adequate.)
- As the stem sprouts, fill in with soil until it is at ground level.
- Do not water the tubers right after planting. This encourages rot. Wait until the sprouts have appeared above the soil, then water.
- Do not spread mulch. Dahlias prefer sun on their roots, plus mulch harbors slugs.
- Tall, large-flower cultivars require support. Place 5- to 6-foot stakes around plants and tie stems to them as the plants grow.
- Dahlias begin blooming about 8 weeks after planting.
Growing Dahlias in Containers
Medium- to dwarf-size dahlias do well in containers that have drainage and are big enough to support the plant at maturity. Generally, a 12x12-inch container will suffice.
- Use a soilless mix and co-polymer moisture-retaining crystals, per the package’s guidance.
- Follow the depth requirements.
- Cover the tuber with a few inches of soil-crystal mix.
- Spray water on the tuber, if necessary, until growth starts.
- Do not water if the soil is damp 1 inch below the surface.
- Fertilize through summer as directed.
- Add soil if the roots become exposed.
Check out our video to learn more about growing dahlias in your garden:
When dahlias are established, water 2 or 3 times a week and more in hot, dry climates. Be prepared to tend to plants before or after rain, when open blooms (especially large ones) fill up with water or take a beating from the wind.
- After sprouting, dahlias benefit from a low-nitrogen, liquid fertilizer, such as 5-10-10 or 10-20-20. Fertilize every 3 to 4 weeks from sprouting in midsummer until early autumn. Do not over-fertilize, especially with nitrogen, or you risk small or no blooms, weak tubers, or rot.
- When plants are about 1 foot tall, pinch out 3 to 4 inches of the center branch to encourage bushier plants and increase stem count and stem length.
- For large flowers, try disbudding: Remove the two smaller buds next to the central one in a flower cluster. The plant will put all its energy into fewer but considerably larger flowers.
- Bedding dahlias need no staking or disbudding. Simply pinch the center shoot just above the third set of leaves to encourage bushiness.
- For more blooms, deadhead as flowers fade; deadheading keeps the flowers blooming for months!
There are about 60,000 named varieties and 18 official flower forms, including cactus, peony, anemone, stellar, collarette, and waterlily. Here are some popular choices:
- ‘Bishop of Llandaff’: small, scarlet, intense flowers; handsome, dark-burgundy foliage; 3 feet tall
- ‘Miss Rose Fletcher’: an elegant, spiky, pink cactus plant with 6-inch globes of long, quilled, shell-pink petals; 4 feet tall
- ‘Bonne Esperance’, aka ‘Good Hope’: dwarf variety that bears 1-1/2-inch, rosy-pink flowers all summer that are reminiscent of Victorian bedding dahlias; 1-foot tall
- ‘Kidd’s Climax’: the ultimate in irrational beauty with 10-inch “dinnerplate” flowers with hundreds of pink petals suffused with gold; 3-1/2 feet tall
- ‘Jersey’s Beauty’: 4- to 6-inch hand-size pink flowers in fall; 4 to 6 feet tall
We recommend checking out the National Dahlia Society for more information about specific varieties.
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When do you plant dahilia seeds? I'm in zone 8.
Hi Courtney,
While dahlias are typically grown from tubers, you can certainly be grown from seed. The only thing to know is that if you collected the seeds from a dahlia you grew, it will not grow true to what you had in the garden. Only tubers will stay true to type. Growing dahlias from seed is how new varieties have been created.
With that being said, you will want to check your last spring frost date for your Zone 8 location and plant the seeds indoors 4 to 6 weeks before that date. Once the threat of frost has passed, you can start by hardening them off (slowly introducing them to outdoor conditions) before planting in your garden or in a container.
In the fall, you can collect the tubers from your dahlia plants and store them over winter to be planted the following spring, as the tubers do not do well in cold winter conditions.
Is there a dahlia for zone 4. I live in Michigan
Hi Katherine,
Dahlias can most certainly be grown in Zone 4, but must be treated as an annual as the tubers will not survive your winters. Plant tubers after the threat of frost has passed in the spring and then lift the tubers to store for the winter following the first frost in the fall.
In terms of what dahlias to plant, you should discuss this with your local garden center to see what is available and/or contact your local cooperative extension to learn what varieties of dahlias thrive in your specific area.
I live in SE PA. Since I've been living here our planting zone has gone from 6 to 7. Usually by the beginning of June we have temperatures in the mid 80's into the 90's. The nights average 60 degrees F. This year we have had highly variable temperatures. Three days of 70's to the 80's with 45 degree nights. Then we got a run of 50–60-degree days with high 30's to mid 40's at night, Only in the last week of June did the temperatures even out. I just planted my dahlia tubers and it is July 1st. Will I get anything close to a bloom this year? This is the first time I have planted dahlias.
Your article shows the most beautiful flowers but I wish you added the name of the variety to the description. I’d love to have the one at the top of the article but have no idea what it’s called. This goes for all your articles showing various plants.
Thanks for your feedback, Jenny! We recommend referring to the National Dahlia Society for more information about specific varieties.
I live near Portland, OR. Do I need to lift my dalias?
Check your hardiness zone. If you are in 7 or above, you should be alright leaving them in the ground.
Six years ago, I bought a package of seed dahlias and planted them in an area in front of our house which is somewhat protected from the weather. The first year they bloomed and were about six inches high. Since then, they have spread over the area and bloomed on their own producing beautiful variety of colors. I have never dug them up after blooming but left them alone. The plants are 12 inches to 3 feet high. I didn't think dahlias spreads. What type of dahlias are these?
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