How to Grow Dahlias: The Complete Dahlia Flower Guide (2024)

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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.

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 betterdrainage.

When to PlantDahlias

• Dahlias will not tolerate cold soil. Plant when the soil reaches 60ºF (15°C) and any danger of frost haspassed.
• Planting dahlias a few days after tomatoes are planted in the ground is a good rule ofthumb.
• 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 incontainers.

How to PlantDahlias

Avoid planting dahlia tubers that appear wrinkled or rotten. Pink “eyes” (buds) or a little green growth are goodsigns.

• 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 eachother.
• Plant medium- to low-height dahlias, usually in the 3-foot tall range, among other summer flowers. Set them 2 feetapart.
• Plant the smallest bedding dahlias, grown from seed, 9 to 12 inchesapart.

Start by digging a 6- to 8-inch deep hole to plant the tubers. It also helps to mix some compost and a handful ofbonemeal into the planting hole. Otherwise, do not fertilize atplanting.

• Set a tuber into the hole with the growing points, or “eyes,” facingup.
• Do not break or cut individual dahlia tubers (as you would withpotatoes).
• Cover the tuber with 2 to 3 inches of soil. (Some say 1 inch isadequate.)
• As the stem sprouts, fill in with soil until it is at groundlevel.
• Do not water the tubers right after planting. This encourages rot. Wait until the sprouts have appeared above the soil, thenwater.
• Do not spread mulch. Dahlias prefer sun on their roots, plus mulch harborsslugs.
• Tall, large-flower cultivars require support. Place 5- to 6-foot stakes around plants and tie stems to them as the plantsgrow.
• Dahlias begin blooming about 8 weeks afterplanting.

Growing Dahlias inContainers

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 willsuffice.

• Use a soilless mix and co-polymer moisture-retaining crystals, per the package’sguidance.
• Follow the depthrequirements.
• Cover the tuber with a few inches of soil-crystalmix.
• Spray water on the tuber, if necessary, until growthstarts.
• Do not water if the soil is damp 1 inch below thesurface.
• Fertilize through summer asdirected.
• Add soil if the roots becomeexposed.

Check out our video to learn more about growing dahlias in yourgarden:

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 thewind.

Dahlia GrowingTips

• 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, orrot.
• 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 stemlength.
• 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 largerflowers.
• Bedding dahlias need no staking or disbudding. Simply pinch the center shoot just above the third set of leaves to encouragebushiness.
• For more blooms, deadhead as flowers fade; deadheading keeps the flowers blooming formonths!

There are about 60,000 named varieties and 18 official flower forms, including cactus, peony, anemone, stellar, collarette, and waterlily. Here are some popularchoices:

• ‘Bishop of Llandaff’: small, scarlet, intense flowers; handsome, dark-burgundy foliage; 3 feettall
• ‘Miss Rose Fletcher’: an elegant, spiky, pink cactus plant with 6-inch globes of long, quilled, shell-pink petals; 4 feettall
• ‘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-foottall
• ‘Kidd’s Climax’: the ultimate in irrational beauty with 10-inch “dinnerplate” flowers with hundreds of pink petals suffused with gold; 3-1/2 feettall
• ‘Jersey’s Beauty’: 4- to 6-inch hand-size pinkflowers in fall; 4 to 6 feettall

We recommend checking out the National Dahlia Society for more information about specificvarieties.

The more you cut dahlias, the more they’ll bloom! For a bouquet, cut stems in the morning before the heat of the day and put them into a bucket of cool water. Remove the stems’ bottom leaves and place the flowers into a vase of water. Place the vase in a cool spot and out of direct sun. Check the water daily. Vase life is about 7days.

Digging Up and Storing DahliaTubers

Dahlias are hardy to Zone 8; in these more temperate regions, dahlias can simply be cut back and their tubers left in the ground through winter, covered with several inches of dry mulch.In Zone 7, some gardeners claim their tubers survive winter in the ground; others have had varied results. It all depends on the severity of winter; native to Mexico, dahlias won’t survive freezing temperatures.→Find your USDA Hardiness Zone here.

In Zones 8 and north, dig up (lift) and store tuberous roots in latefall; tubers can be expensive, and this willsave you the money that would otherwise gointo buying new ones each year.See your fall frost dates

• Dahlia foliage blackens with the first frost. Take it as a warning to begin digging up the tubers. Complete the task before a hardfrost.
• Cut off blackened foliage, leaving 2 to 4 inches of topgrowth.
• Carefully dig around tubers with a pitchfork, garden fork, or shovel. Avoid damagingthem.
• Lift the clump and gently shake off thesoil.
• Cut off rottentubers.
• Leave clumps outside in the sun upside down to dry naturally for a fewdays.
• Pack them in loose, fluffy material (e.g., vermiculite, drysand).
• Store in a well-ventilated, frost-free space: 40º to 45ºF is ideal,35º to 50ºF isacceptable.
• Check on the Dahlia tubers occasionally over the winter. Remove any tubers that have started to rot before the decay spreads to healthytubers.

Readying forSummer

In spring, separate healthy tubers from the parent clump and discard wrinkled or rotten ones. Plan to plant the survivors. Each tuber must have at least one “eye” or piece of the crown attached, or it will not develop into a blooming plant. The eyes are little pink bumps at the base of the stem. →See our gardener’s article on how to unpack and divide your stored dahlia tubers!

If this all seems like too much bother or you do not have the right storage place, skip it all and treat dahlias as annuals, buying newtubers in thespring.

Catherine Boeckmann