Dahlias are beautiful flowers that bloom from midsummer to fall. They bloom in a rainbow of colors and range in size from delicate 2-inch pom-poms to giant 15-inch “dinner plates.” Most varieties reach a height of 4 to 5 feet.
Check out our full guide on how to grow Dahlias and care for these gorgeous, colorful blooms that bloom from midsummer to fall, when many are past their prime.
Table of Contents
About Dahlias
Dahlias belong to the Asteraceae family, which also includes sunflowers, daisies, chrysanthemums, zinnias and, of course, aster.
Dahlias inspire awe and a good mood. Growing vegetables? Put a row of dahlias on the border and they won’t cover your food. They make beautiful cut flowers.
Dahlias like humid, temperate climates. While dahlias are less suited to extremely hot climates (like South Florida or Texas), they will brighten any sunny garden with at least 120 days of the growing season.
Tubers are planted underground in late spring. In cooler regions of North America, they are considered a tender perennial. They are indeed hardy in hardiness zones 8 through 11, although gardeners in zones 6 and 7 may also be lucky enough to keep them in the ground. In cooler regions, dahlias can either be treated as annuals or dug up after the first frost and stored indoors for the winter. (See which hardiness zone you are in!)
Picking your favorite dahlia is like browsing a box of buttons. Not only do dahlias come in a rainbow of colors, but they range in size from delicate 2-inch lollipop-style pom-poms to giant 15-inch “dish” flowers. Most varieties grow to be 4 to 5 feet tall.
Planting Dahlias
Dahlias thrive in 6 to 8 hours of direct sunlight, especially the morning sun. They benefit from windbreaks because strong winds can blow over tall dahlias without support. When planting, consider the size at maturity.
Dahlias grow best in rich, well-drained soil with a pH of 6.0 to 7.5. Amend heavy clay with old manure or compost to lighten and loosen the soil texture for better drainage.
When to Plant Dahlias
Dahlias are not hardy soil. Plant when soil reaches 15°C and all danger of frost has passed.
Planting dahlias a few days after tomatoes are in the ground is a good rule of thumb.
Some gardeners start growing tubers in containers a month early to get into the season. Medium to dwarf dahlias do well in containers.
How to Grow Dahlias
You can grow these shrubs from seeds, but you will get a random result. For flowers that meet your color and shape needs, buy and plant bulbs.
Sowing Dahlia Seeds
Dahlias are often grown as bulbs, as this is a faster and generally more reliable way to grow, but dahlias can also be grown from seed.
Dahlia seeds should be sown covertly between February and April. Sow seeds 0.5 cm deep in moist compost trays. Keep in a warm place, about 15-20°C (60-68°F). Keep moist.
When large enough to handle, transplant seedlings into deeper trays or separate small pots.
Continue planting in cool but frost-free conditions. After the risk of frost in May and June has passed, gradually harden the seedlings before planting.
Growing Dahlia Bulbs in Pots
Dahlia bulbs can be started in covered pots in March or April and then transplanted into the garden in late May and June.
Start by filling a 2- or 3-quart pot half-full with all-purpose peat-free compost. Place the bulbs in the pot, center up, and cover with more soil. Don’t forget to label and water the pots lightly, then place them in a warm and frost-free spot – a greenhouse is ideal. Do not water again until they start shooting, then water lightly.
After 2-3 weeks, new shoots will begin to appear – some varieties may take longer. As these shoots grow, pinch the top of the main branch (you can use a sharp knife or pinch with your thumb and forefinger) onto the top pair of leaves.
As the plant continues to grow, remove all but the five shoots that sprout from the bulb. This can feel harsh, but if you only have five stalks, each can develop and thrive, and the result is a lot of shoots!
Growing Dahlia Bulbs In The Ground
If you don’t have room to plant the bulbs in pots first, you can plant them directly in the ground in the spring—just make sure the frost is over soon.
Plant the tubers below the soil surface, making sure they are about 75 cm (30 inches) apart, depending on the variety.
Use sturdy wood stakes as stakes when planting, as they can grow quite large plants when fully grown. Cover or protect with bells or garden wool. This is especially important if the leaves emerge before the frost has passed.
Whether you’re growing dahlia bulbs outside the garden or under cover, you’ll need to pinch off the top of the main stem once three pairs of leaves have grown. You can use a sharp knife or squeeze and push out the top pair of leaves between your thumb and index finger.
Growing Dahlia Plants
If you are growing a dahlia grown from a tuber or purchased as a plant in a 2- or 3-liter pot, you can plant it outdoors after the danger of spring frost has passed. Dig a planting hole for each plant in a sunny, shaded location.
The holes need to be at least 30 cm (1 ft) square and 30 cm (1 ft) deep, and the plants should be about 75 cm (30 in) apart, depending on the variety. Add plenty of organics to the wells. For heavy clay, add gravel to the planting hole. Place the dahlia in the hole with the bulb just below the soil surface and fill in around the root ball.
Use stakes when planting, as they can grow into fairly large plants when fully grown. You’ll need a sturdy stake (not just a bamboo pole) to support each plant, and it’s best to hammer it in first and then set the plant aside.
As they grow, pinch off the growing tips once three pairs of leaves have emerged to encourage branching.
If the stakes are in place when planting, you can continue to tie them up every few weeks. Dahlias grow very quickly once they start to grow and can easily break in the wind and rain if not securely fastened.
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Growing Dahlias in Pots
Dahlias are usually planted face down in pots and then transplanted into the garden, but dahlias can also be grown in pots.
Make sure to choose a slightly compact dahlia variety, as some dahlias can grow to over 1.5m. Then choose a container that is at least 30 cm (1 ft) in diameter and 40 cm (15 in) deep for optimal growth. Use an all-purpose peat-free compost and add a slow-release fertilizer to encourage growth.
Plant the dahlia tubers as you would and plant them in the soil, just below the surface of the compost. Then add a stake, tag and well.
If you’re starting your dahlias in March or April, place the pots in a bright, warm, frost-free spot. If you are starting in early summer, keep the pot outside.
How to care for dahlias
Irrigation
Dahlias like moist soil. In times of drought, water them once a week with plenty of flood water rather than light sprinkling. If your dahlias are in pots, water them often—every day during droughts. They are thirsty plants.
Fertilize
If your dahlias are in pots, either use a slow-release fertilizer or fertilize every two weeks with a liquid comfrey or algae fertilizer. Start after the first month.
Indicate
All dahlias should be planted next to stakes. Make sure to keep adding dahlias every few weeks. Dahlias grow very quickly once they start to grow and can easily break in the wind and rain if not securely fastened.
Dead
Unless you’re picking every dahlia for the house, they need to die on a regular basis, which encourages blooming. To die, go down the stem and cut just above the first pair of leaves you hit.
Spread
Dahlias are easily propagated from basal cuttings. In the spring, once the bulbs begin to sprout, choose strong, healthy shoots that are about 3 inches long. Using a clean, sharp knife, remove them along with a small portion of the mother bulb.
Remove all leaves except the top pair of leaves and pinch out the top.
Prepare a 1-quart pot and mix the compost and grit (3 parts compost to 1 part grit). Place each cut on the edge of the pot, with the leaves just above the top of the compost, and spaced so they don’t touch each other.
Water from above to settle the compost. Then place them in a bright but out of direct sunlight, warm place or heated greenhouse. Label the pot.
After about 3-4 weeks, the cuttings will take root, carefully plant each cutting at a time in a 7.5 cm (3 in) pot and continue to grow, after all danger of frost has passed.
With regular fertilization and watering, plants grown from cuttings will bloom and form bulbs later in the same summer.
Through the above article, Answer The Question hopes that you will know how to plant trees to make your garden more beautiful.
