Echinocereus poselgeri (Dahlia Cactus) is a shrubby cactus, initially erect, later sprawling or clambering. The stem is very tall and…
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.
Check out our video to learn more about growing dahlias in your garden.
Pinching, Disbudding, and Staking
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.
Unless you live in a warmer region, 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 the money that would otherwise go into buying new ones each year.
If you live in an area where your ground doesn’t freeze, you don’t need to dig up your tubers. The general rule is: If you live in USDA Hardiness Zone 8 or warmer, you can leave dahlias in the ground. In Zone 6 or colder, dig them up. In Zone 7, you may be able to get away with just covering the plants with a thick layer of leaf or straw mulch, but if a freeze hits, you may lose them.
When to Dig Up Tubers
Dig up dahlias before the first hard freeze. A light freeze (32°F / 0°C) will kill the foliage, but a hard freeze (28°F / -4°C) will kill the tubers, too. 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:
That’s it! Cut rotten tubers off the clump and leave the clumps outside in the sun upside down to dry naturally.
How to Store Dahlia Tubers
Re-planting Tubers in Spring
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.
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:
Image: Kidd’s Climax. Longwood Gardens
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)
With their intense color, strength, and ability to keep flowering until the first frosts, dahlias are easy to grow and bring life to your garden. Dahlias like well-balanced and composted soil, and full sun. With 42 different species and thousands of cultivars, dahlias offer plenty of variety. Variations in color, flower form, size, and foliage make it easy to find one you'll love.
Dalightful® Georgia Peach (Dahlia variabilis) Photo by: Proven Winners.
If you want to get a head start on your dahlia growing season and encourage earlier blooming, consider starting your new dahlias indoors as potted plants. The best time to do this is in early spring, about six to eight weeks before you plan to move them outside. Of course, you can wait until after the last expected frost and plant your dahlias directly in the ground or into your outdoor decorative pot, but your window of wonderful bloom time will be shortened. If you'll start your dahlias indoors, use a one-gallon pot to give the plant's roots plenty of room to grow, says Rowe. Just make sure the pot has bottom drain holes for proper drainage. Start by filling the pot with well-draining garden soil that is moist, but not wet. Then plant one tuber per pot on its side, about two to three inches deep. "You can choose to leave the eye showing out of the soil, but at least cover the tuber body," says Rowe. Lastly, place your pot in a warm, sunny spot (at least 60 degrees) and don't water until the sprout shows above the soil.
Should your indoor space allow, you can also plant your tubers directly into the decorative containers you plan to display them in once outdoors. Just make sure to keep it inside until after the last expected frost. Rowe suggests, "If you plan to grow your dahlia to full-size in a container, ensure that it's a large one, at least 15 inches across the top and at least 12 inches deep so your dahlia has space to grow a large root ball." Another must-have according to the expert? Great drainage. "Make sure the container has good drainage holes in the bottom so the water passes through the pot and doesn't collect." The tubers will rot in standing water.
Dahlias are the favorite of many gardeners – and no wonder. These exciting flowers are available in a wide range of bright colors. Actually, no other garden flower can match their range of colors and sizes!
The Dahlia’s flowering period also contributes to its great popularity: they can be adding color to your garden from the end of July until the first frost – long after other flowers are spent.
Within the dahlia group as a whole, the Cactus dahlias have the most exceptional flowers. They have beautiful ‘spiny’ petals that are rolled up along more than two-thirds of their length. Sometimes, the petals are straight from the base to the tip, but they can also curve inward or outward. The petals are often narrow and pointed, and some have deeply incised tips. These are the ones known as spider dahlias, and they make real eye-catchers!
The petals are not top-heavy because they contain little water. This means that dahlias remain standing up nice and straight even when it rains.