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Growing Dahlias
How to Plant, Grow, and Care for Dahlias
How to Plant, Grow, and Care for Dahlias
Grow dahlias for gorgeous, colorful flowers that bloom from midsummer through autumn, when many plants are past their best! The tubers are planted in the ground in late spring. In colder zones, you do need to dig up and store the tubers in the fall if you wish to grow them as perennials (or, treat as annuals). Here’s how to plant, grow, and store dahlias.
Dahlia is a genus of tuberous plants that are members of the Asteraceae family; related species include the sunflower, daisy, chrysanthemum, and zinnia. They grow from small tubers planted in the spring. Picking a favorite dahlia is like going through a button box. As well as coming in a rainbow of colors, dahlia flowers can range in size from petite 2-inch lollipop-style pompoms to giant 15-inch “dinner plate” blooms. Most varieties grow 4 to 5 feet tall.
They are considered a tender perennial in cold regions of North America. They are only winter hardy in planting zones 8 to 11. Gardeners in zones 2 to 7 can simply plant dahlia tubers in the spring and either treat them as annuals or dig them up and store for winter. Dahlias love moist, moderate climates. Though not well suited to extremely hot climates (southern Florida or Texas), dahlias brighten up any sunny garden with a growing season that’s at least 120 days long.
Planting
When to Plant Dahlias
- Don’t be in a hurry to plant; dahlias will struggle in cold soil. Ground temperature should reach 60°F. Wait until all danger of spring frost is past before planting. (We plant them a little after the tomato plants go in.)
- 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.
- Order dahlia tubers in early spring. This gives gardeners in colder zones time to get them growing in a sunny window. Or, skip the potting and simply plant the tubers in the ground after the spring weather has settled and the soil has warmed.
Choosing and Preparing a Planting Site
- Select a planting site with full sun. Dahlias grow more blooms with 6 to 8 hours of direct sunlight. They love the morning sunlight best. Choose a location with a bit of protection from the wind.
- Dahlias thrive in rich, well-drained soil. The pH level of your soil should be 6.5-7.0, slightly acidic.
- If you have a heavier (clay) soil, add in sand, peat moss, or aged manure to lighten and loosen the soil texture for better drainage.
- Large dahlias and those grown solely for cut flowers are best grown in a dedicated plot in rows on their own, free from competition from other plants. Dahlias of medium to low height mix well with other summer flowers. If you only have a vegetable garden, it’s the perfect place to put a row of dahlias for cutting (and something to look at while you’re weeding!).
How to Plant Dahlias
- Avoid dahlia tubers that appear wrinkled or rotten. Pink “eyes” (buds) or a little bit of green growth are good signs. Don’t break or cut individual dahlia tubers as you would potatoes.
- Bedding dahlias can be planted 9 to 12 inches apart. The smaller flowering types, which are usually about 3 feet tall, should be spaced 2 feet apart. The taller, larger-flowered dahlias should be spaced 3 feet apart. If you plant dahlias about 1 foot apart, they make a nice flowering hedge and will support each other.
- The planting hole should be slightly larger than the root ball of the plant and incorporate some compost or sphagnum peat moss into the soil. It also helps to mix a handful of bonemeal into the planting hole. Otherwise, do not fertilize at planting.
- Dig a hole that’s about 6 to 8 inches deep. Set the tubers into it, with the growing points, or “eyes,” facing up, and cover 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.
- Tall, large-flowered cultivars will require support. Place stakes (five to six feet tall) around plants at planting time and tie stems to them as the plants grow.
- Dahlias start blooming about 8 weeks after planting, starting in mid-July.
- Do not water the tubers right after planting; this encourages rot. Wait until the sprouts have appeared above the soil to water.
- Do not bother mulching the plants. The mulch harbors slugs and dahlias like the sun on their roots.
Care
How to Grow Dahlias
Watering
- There’s no need to water the soil until the dahlia plants appear; in fact, overwatering can cause tubers to rot. After dahlias are established, provide a deep watering 2 to 3 times a week for at least 30 minutes with a sprinkler (and more in dry, hot climates).
- Like many large-flower hybrid plants, the big dahlias may need extra attention before or after rain, when open blooms tend to fill up with water or take a beating from the wind.
Fertilizing
- Dahlias benefit from a low-nitrogen liquid fertilizer (similar to what you would use for vegetables) such as a 5-10-10 or 10-20-20. Fertilize after sprouting and then every 3 to 4 weeks from mid-summer until early Autumn. Do NOT overfertilize, especially with nitrogen, or you risk small/no blooms, weak tubers, or rot.
Pinching, Disbudding, and Staking
- When plants are about 1 foot tall, pinch out 3-4 inches of the growing center branch to encourage bushier plants and to increase stem count and stem length.
- If you want to grow large flowers try disbudding—removing the 2 smaller buds next to the central one in the flower cluster. This allows the plant to put all of its energy into fewer but considerably larger flowers.
- Bedding dahlias need no staking or disbudding; simply pinch out the growing point to encourage bushiness, and deadhead as the flowers fade. Pinch the center shoot just above the third set of leaves.
- For the taller dahlias, insert stakes at planting time. Moderately pinch, disbranch, and disbud, and deadhead to produce a showy display for 3 months or more.
Winter Care
- Dahlia foliage blackens with the first frost.
- Dahlias are hardy to Zone 8 and can be cut back and left in the ground to overwinter; cover with a deep, dry mulch. Further north, the tuberous roots should be lifted and stored during the winter. (Some readers find, however, that dahlias will survive in Zone 7 if the winter isn’t too severe.)
- See Harvest/Storage (below) for more information.
Pests/Diseases
- Slugs and snails: Bait 2 weeks after planting and continue to bait throughout the season.
- Mites: To avoid spider mites, spray beginning in late July and continue to spray through September. Speak to your garden center about recommended sprays for your area.
- Earwigs and Cucumber Beetle: They can eat the petals though they do not hurt the plant itself.
- Aphids
- Deer: Find a list of deer-resistant plants to grow around your dahlias.
- Powdery Mildew: This commonly shows up in the fall. You can preventatively spray before this issue arises from late July to August.
Harvest/Storage
Dahlia Bouquets
Dahlias are beautiful in a vase. Plus, the more you cut them the more they will bloom. To gather flowers for a bouquet, cut the stems in the morning before the heat of the day and put them into a bucket with cool water. Remove bottom leaves from the stems and place the dahlias in a vase. Put the vase in a cool spot and check the water daily. The bouquet should last about a week.
Digging and Storing Dahlias for Winter
Unless you live in a warmer region of the USA, you have to dig up dahlias in late fall before there is a hard frost in your area. Native to Mexico, Dahlias won’t survive freezing temperatures. Digging and storing dahlias is extremely easy and simple, and will save you a lot of money.
If you live in an area where your ground doesn’t freeze (such as California and Florida), you don’t need to dig up your tubers. The general rule is: If you live in USDA Zone 8 or warmer, you can leave dahlias in the ground.
When to Dig Up Tubers
Dig up your dahlias before your hard frost. See your fall frost dates.
A good indication of when to dig your tubers up is when the plant starts to turn brown and die back.
How to Dig Up Tubers
Digging up tubers is easy.
- After fall frost has blackened the foliage, cut off all but 2 to 4 inches of top growth.
- Carefully dig around tubers with a pitchfork (or shovel) without damaging them.
- Lift and gently shake the soil off the tubers.
That’s it! Cut rotten tubers off the clump and leave the clumps outside in the sun upside down to dry naturally.
Storing dahlia tubers
- Pack in a loose, fluffy material (vermiculite, dry sand, Styrofoam peanuts).
- Store in a well-ventilated, frost-free place—40 to 45º F is ideal, 35 to 50º F is acceptable.
Re-planting tubers in spring
- Take out the tubers in the spring, separate healthy tubers from the parent clump, and plant in the garden. Each tuber must have at least one “eye” or a piece of the crown attached or it will not develop into a blooming plant. The eyes are located at the base of the stem and look like little pink bumps.
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 digging and storing, and just start over by buying new tubers in the spring.
Recommended Varieties
There are about 60,000 named varieties and 18 official flower forms including cactus, peony, anemone, stellar, collarette, and waterlily. The American Dahlia Society recognizes 15 different colors and color combinations. Here are some popular choices:
- ‘Bishop of Llandaff’: small, scarlet, intense flowers with handsome, dark-burgundy foliage
- ‘Miss Rose Fletcher’: an elegant, spiky, pink cactus plant with 6-inch globes of long, quilled, shell-pink petals
- ‘Bonne Esperance’, aka ‘Good Hope’: a foot-tall dwarf that bears 1-½-inch, rosy-pink flowers all summer that are reminiscent of Victorian bedding dahlias (though it debuted in 1948)
- ‘Kidd’s Climax’: the ultimate in irrational beauty with 10-inch “dinnerplate” flowers with hundreds of pink petals suffused with gold
- ‘Jersey’s Beauty’: a 7-foot tall pink plant with hand-size flowers that brings great energy to the fall garden.
Image: Kidd’s Climax. Longwood Gardens
Wit & Wisdom
- The dahlia was named for Anders Dahl (Swedish botanist), born on March 17, 1751.
- In the 16th century, dahlias grew wild on the hillsides in parts of Mexico. There, they were “discovered” by the Spanish, who remarked on the plant’s beauty.
- Both dahlia flowers and tubers are edible. The tubers taste like a cross between a potato and a radish.
The Dahlia you brought to our isle
Your praises forever shall speak
‘Mid gardens as sweet as your smile
And colour as bright as your cheek.
–Lord Holland (1773–1840)
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Reader Comments
Leave a Comment
Novice Dahlia Grower
I live in zone 6a. I would like to create a dense collection of dahlias to grow next to my fence - more of a bush type of look rather than individual stems. I don’t want it too short because I have some 1-11/2 foot allums along the boarder. Any suggestions?
Dahlias
Try planting a few different varieties with differing heights, staggering them in such a way that they still have room for themselves, but give the appearance of a dense hedge of dahlias.
Check out Burpee’s selection of dahlias here—you can sort by height to see which would work best for you!
Dahlias
Just printed up some infor on the care of Dahlias for a neighbor of mine.
Storing Dahlias
Ive bought a dahlia in a pot. Its probably to late to plant it in the garden. So can i just leave it in the pot and store it in my none heated greenhouse over winter and plant it in the spring.
Overwintering Dahlias
Hi Patricia,
If you live in USDA Zone 8 or higher, you can leave the dahlia in the pot or in the ground over the winter. In regions that experience freezing or below freezing temperatures, follow the instructions under Harvest/Storage and Taking Up the Tubers, which can be found above on this page. We hope this helps!
Save the Dahlia bulbs
Hi The Editors,
I live in zone 10, my Dahlias were planted in the large container. The blooming season is ending soon and I will cut the plants down to the base. Please teach me:
- Can I keep the tuber in the container until next year?
- It's very warm here, do I need to cover them with mulch?
- Can I put some small containers with planted flowers on top of the tubers? It means the tubers will be watered.
Thank you for your help.
Question about planting dates
I purchased some dahlia bulbs. Can I plant them in the summer or must I wait until the spring after the last frost? I’m in northern Ontario, Zone 3B, according to planthardiness website. Would putting down mulch before the winter help? Would the snow provide enough insulation? Would it be better for me to plant these bulbs in pots and take them inside during the winter? Thanks for your help.
too late to plant dahlias?
Dahlia bulbs are planted in the spring once risk of frost has passed. They will grow quickly and the plants will be blooming by mid to late summer.
In your region, dahlias also need to be lifted out of the ground for winter storage if you want them to bloom next year. Many gardeners treat dahlias as annuals.
So, given where you live, you could try storing the tubers over the winter. If properly stored (usually in a vermiculite or peat moss), they should be fine.
First buds
I just wanted to comment that it takes alot longer than 8 weeks to show the first buds. I started my dahlias from tubers in late February and today July 13th I've finally had my first flower (after removing the first buds as recommended). These dahlias had better be worth the wait because the enormous amount of work that has gone into babying them(constant fertilizing, adding micronutrients, soil amendments, water, insect treatments, staking, etc.) has been utterly frustrating. I live in zone 7 and at this rate I will be lucky to have 3 months of growth. I'm just not sure it's worth the effort.
Dahlias
When dahlias bloom has a lot to do with the soil warmth and how deeply they are planted (ensure an eye is present on each tuber clump). We would suggest early blooming variety if possible. We have had late varieties that never bloomed before the first frost in the fall! Also: Once the leaves begin forming and the plants are 3 to 4 inches tall, pinch the terminal bud just above the second pair of leaves. This will produce two main stems. Remove the buds when the flower buds are visible. This will increase the bloom size of the leader bud and improve the flower stem formation. Flower buds come in sets of three. The central leader bud will produce the largest bloom. There will be a smaller flower bud on each side of the leader bud. Remove these side buds by pinching. Further down the same stem, two more buds will be found in the leaf axils and these, too, should be removed.
I have new Dahlia plants.
They have started growing, but something is eating the leaves and stripping the stem. What can I use to spray them, to kill whatever is eating the plants?
Pests on Dahlias
Monitor the plants for any beetles, caterpillars, or slugs that could be munching on the foliage. If you don’t see any culprits, try using a pesticide like neem oil or an insecticidal soap.
after I cut the flower I find
after I cut the flower I find that there are insects in the flower , how do I get rid of the few insects before I bring the cut flowers in the vase inside?
bugs away!
You can also cut the flowers in the morning and place the stems in a bucket of water outdoors in the shade. The insects should leave without your doing anything else. Before you bring the flowers into the house, inspect them and, if necessary, shake them gently. Remove any bugs by hand or with a small soft paintbrush.
Dahlias from seed.
I'm a little confused because the article (and every other article I've read on the subject) refers to tubers and I've only ever grown dahlias from seed. The first time I grew them from seed I assumed that tubers would form and I could dig them up in the autumn and store them for the following year. However, I was disappointed to find nothing but a mass of roots which hardly seemed worth saving so, since then, I've just continued to sow them every spring and let them die off naturally when the frost comes. Can you explain why my dahlias don't form tubers?
Height of Dahlias
Hi I've had my beautiful Dahlias about 3 years now. I leave them in the bed in the winter and they're as thick as a forearm now!! My issue is I'd like the bed to be a cushion of flower heads at about 3 foot. Last year most of them grew to 5/6 foot so there was just a wall of green next to the patio. They're tall varieties but is there any way to keep them shorter but still full of flowers??
Thanks
Dahlias
I've been completely in love with Dahlias ever since my husband got me some for our Thanksgiving centerpiece, and now I want to add them to my garden. It's really good to know they don't do well in cold soil; I'll definitely wait until later spring before planting any. Checking the soil pH is a good idea, as well, because I really want these to thrive, so I'll be sure to look into that.
lifting Dahlias early before frost
It's November and I have not had a hard frost. Can I lift the Dahlias and store for next winter before a frost?
I live in zone 7, outside Washington DC
Accidentally pulled bulbs while planing in pot
Hi!
I just bought a Dahlia and when I went to transfer the plant to a pot the bottom of the soil got stuck and the bulbs were disconnected from the plant. Will this kill the plant?
re plant a fully grown plant
I noticed one of my dahlia plants is not growing very tall, i think because the water is not getting to it, i would like to uproot the plant and put in a large pot. thoughts please....
replanting the dahlia
I bought a dahlia a large one with big flower do I need to re pot the plant, the flowers are hanging down
Dahlias not producing buds
I have 3 Dahlia plants. Only one is producing buds and flowers. All three were planted at the same time. The other 2 plants looks healthy, but no buds or flowers. What's up with this?
Dahlias
Is it recommended to cut down the first shoots to encourage more shoots to grow,Ihavebrought the tubers on prior to planting out.
Pinching Dahlias
If you haven’t planted the tubers yet, then yes, you should trim the shoots down to 1 inch before planting. It’s recommended to pinch back stems only slightly once they have developed 3 to 4 sets of leaves. This will encourage the plant to branch out from the stems, giving you a fuller plant.
Potted Dahlias
What is the care for potted dahlias?
dahlias in pots
Growing in a pot/container is essentially the same as in the ground. Make sure that the pot is large enough to give the tubers room to spread out, and if staking/support is needed, arrange it in the pot when you plant the tuber (as if you were planting in the ground). Staking later risks injury to the tuber and potentially loss of it or the bloom.
Growing in pots
Can l over winter dahlias in pots in a garage or greenhouse l live in the uk
Dahlias in pots??
I live inOlive Branch ,Mississippi. ( right by Memphis Tennessee ). Can I grow Dinner plate Dalias in Large pots?( I’ve already planted & they are starting to come up....3 inches tall) my pots sre 24 inched wiwide & 3ft tall.
Dahlias
I planted 6 tubers and now I have 30 plants. What do I do?
from 6 plants to 30
It’s not entirely clear: If you now have 30 plants in the ground, you can lift the tubers and divide them. This is best done in spring or fall. Use a sharp knife to cut the tubers apart. Note that only those with an eye (a dormant bud) will grow stems, so you can cut large clumps of tubers instead of discarding single ones without eyes. Let the roots dry for a day or so before storing (see above) or planting elsewhere.
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