Planting, Growing, and Caring for Dahlias
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Dahlias are breathtakingly gorgeous flowers that come in every color of the rainbow. The tubers are planted in late spring. Learn more about planting, growing, and caring for dazzling dahlia flowers.
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 United States, they are considered perennials 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 the garage until spring. Learn how to dig up dahlias in the guide below.
Planting
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:
Growing
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.
Dahlia Growing Tips
- 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!
Types
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.
Catherine Boeckmann
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My dahlia is in a container. It is loaded with buds but they don’t make flowers. What is the problem?
Hi Eva,
There could be a few reasons why your dahlia buds are not opening. The first thing would be to examine your watering practices. Waterlogged roots from excessive water can affect the buds’ ability to open. Also, if your dahlia was planted in poorly draining potting mix or a container that holds water it can lead to too much water that will hinder your buds from turning into flowers. A lack of water can also be an issue, as container planted dahlias need consistent watering because the potting mix dries out a lot faster than those planted in the ground.
If your watering schedule is consistent, it could be an underlying pest issue. If the stems and leaves appear normal but buds are not opening, check them for small holes to determine if thrips or earwigs have punctured or chewed them. Buds that have been repeatedly affected by these pests might not open properly.
Another issue could be excess fertilization in the form of too much nitrogen. If the plant is overfertilized, it will grow luscious foliage at the expense of flowers.
Hope this helps!
I bought two medium size dahlias and repotted in a medium size pot each in April. I live in Gibraltar where we have a hot climate. they were beautiful and blooming, I have always kept dahlias, I now have them on my balcony. Suddenly they have started to die down and all the foilage has dried up. I have removed all the dead stalks and foilage and now only have the tuber. Not sure what has happened here, will they survive. I am watering and feeding once a week, but its been 3 weeks now and I see no sign of life. Appreciate any feedback. thanks
Hi, Subia. We are sorry to hear about your dahlias. They can be fickle plants in hot climates, as they prefer warm days and cooler nights. Here are a few things to try to revive your plants: Add organic matter to your containers. Keep watering (do not soak), and try adding some mulch on top to cool them down. Also, if your dahlias are in full sun, move them so that they get some shade. If all else fails, we highly recommend looking into getting a heat-tolerant variety. They may perform better in your climate.
June 11, 2024 - I just bought a "potted" Dahlia that has the most beautiful blooms. I live in zone 6 and want to keep it in a container so I don't have to dig the tubers and can move it inside to winter. Can I move it to a larger pot/container? If so, can I re-pot it now or wait until it finishes blooming? Thank you.
Hi Dollie,
Dahlias certainly are beautiful. You definitely want to wait until it has finished blooming, but it is best to wait until the first frost has hit or the leaves have turned brown. At that point, you could transplant your tuber to a new container with fresh potting mix and store indoors in a cool, dark room for the winter. But it would probably make more sense to simply remove the tuber from the current container and store it as outlined above for the winter before then putting the tuber in a new container in the spring. That way you don’t have to lug the new, larger container (which will be heavier) in this fall and out again next spring.
Good luck!
I live in NE Indiana. Last fall a friend surprised me with a beautiful bouquet of Dahlias and I fell in love with them. I am a new at gardener. I want to add Dahlias to my gardens but am overwhelmed by all of the information below. Is growing Dahlias as difficult as it appears? Perhaps I should get a few more years of gardening experience before attempting them? What are your thoughts please?
Growing dahlias is so easy and the sprout up pretty quickly. I planted mine well after Easter and several are over 3 feet high and have beautiful blooms. I do try to cut back and leave just one bloom per stem, making the ones you keep larger. Enjoy!
Hi Marleene,
It’s not hard to see why you fell in love with dahlias!
Gardening is all about trying new things, so if you want to grow dahlias in your garden you should try it. Growing dahlias will be easier if you plant tubers and not start from seed. For the first year, you can start small and plant only a couple tubers to see how it goes.
There are a few things you want to remember: Don’t plant your tubers until after all threat of frost has passed. Plant them in an area that gets lots of sunlight (6 to 8 hours). When you do plant, make sure to follow the steps outlined above.
Since your location is in growing zone 6a, you will want to treat your dahlias as an annual, meaning you want to lift them from the garden in the fall and store indoors during the winter months and then plant again in the spring.
And to get an idea of what dahlia varieties grow best in your area, check with your local gardening center or reach out to your local cooperative extension for guidance.
Hope this helps. Good luck!
What about Dahlia seeds? I would also love some guidance on beachside gardening. Thanks
