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!
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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I live in zone 8 I would like to plant Dahlis next year, what would be a month when this can be done. It does get pretty hot in Amite, La. July, Aug.and ?September. are our hottest months. I would greatly appreciate your suggestion.
Hi,
I read that Dalias can be left in soil over the winter in zone 8, but I could not find a zone map, so here is my question. Can I leave my Dalias in in Brooklyn NY?
Thanks,
Erica
Sorry, Erica, You are not in Zone 8. See here where you are (and where 8 is): http://www.almanac.com/content/plant-hardiness-zones
I grow Dahlias in the same bed every year, and they do well, whether new tubers or replanted. We get plenty of Sun, a bit in the early morning then all the rest of the day after noon.
This year, I planted, indoors, in pots as I usually do, but a bit late.
I got good growth but few flowers, until late season.
This summer was hot: did they stop flowering because of the heat ?
I use a soaker hose on them regularly to make sure they water to the roots. Too much water?
Or is it the soil. I usually plant bulbs in the fall, for spring bloom, but also had a bad year because the mice/chipmunks found them. Is that the problem?
I usually amend the soil and have a good tilth, in what was clay soil: I've added sand, composted manure, and peat over the years, to get it to this friable state, but did not add anything this year.
It's a puzzle as the short varieties just did not bloom, the taller bigger sizes were tall, but very few flowers and small.
Lastly, I added a small amount of 10:10:10 when planting, but no more until late after I saw few flowers. Then I added a liquid 0:10:10 fertiliser
Hi
I planted a dahlia this year from seed, and when I dug it up today there were the tubers.
Is it possible to save them for next year?
Should I deal with them the same way as for dahlias that are planted from tubers?
thanks.
I planted my dahlias in pots this year (from MN). After a hard frost, I am going to cut them down to the dirt and place the pot, with roots in soil, in the garage or similar space. Then in the spring I will set them out, after frost has passed. I thought this would be a good experiment. My father used to dig them up and put them in vermiculite and store them in the garage in a tube with a cover. He had beautiful dahlias in the spring. I don't want to go through all that fuss, so introducing a new experiment. What are your thoughts? Thanks!
Experimenting can be fun, but we suggest doing so with just a few of your tubers, the rest should be taken out of the soil. You want them to be cool and dry. The soil will have moisture in it, which could cause the dahlias to rot.
when to plant dahlias for best results--Are they bulbs?
Dahlias are tubers. They should be planted in the early spring after the threat of frost has passed. In cold climates, they should be dug up in the fall and stored in a cool dry place like a garage. They can’t withstand freezing temperatures. In warm climates, they can stay in the ground year-round.
My balcony is very bright and hot almost the whole day but it recieves only filtered sunlight and no direct sunlight due to a building nearby.Does dahlia grow and bloom good in my balcony? I am from India where it is hot almost the whole year except for few days of winter and rainy seasons.
