In this article you can find easy steps how to grow dahlias in your garden.
In colder zones, lift your dahlias after the first frost! See our full guide on how to plant, grow, and care for these stunningly gorgeous, colorful flowers that bloom from midsummer through autumn, when many plants are past their best!
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.
Dahlias love moist, moderate climates. Though not well suited to extremely hot climates (such as southern Florida or Texas), dahlias brighten up any sunny garden with a growing season that’s at least 120 days long.
The tubers are planted in the ground in late spring. They are considered a tender perennial in cold regions of North America. They are reliably winter hardy in hardiness zones 8 to 11, though gardeners in zones 6 and 7 may have luck keeping them in the ground as well. In more northern zones, dahlias can either be treated as annuals or dug up after the first frost and stored indoors for winter.
How to grow dahlias
Dahlias require a fertile, moist but well-drained soil, and a sunny, sheltered spot. The taller varieties need staking. In autumn, dig up the tubers and overwinter them in a frost-free place, such as a greenhouse or a shed. Bring them back into growth in early April, then plant out in the garden from May onwards.
Where to grow dahlias
Dahlias like a sheltered spot, with as much sun as possible – a south or west facing border is ideal. Dahlias are not fussy when it comes to soil. For best results grow in any fertile, moist but well-drained soil. Enrich the soil with some organic matter, such as well rotted manure. If you’re growing on heavy clay, add some grit to the planting hole. If you’re growing dahlias in pots, use a good quality, peat-free multi-purpose compost.
How to Grow dahlias from tubers
Dahlia tubers are available to buy from February. Most garden centers have a good selection but for the best range, buy online.
In early April, you can put all of your tubers in a large, shallow tray, lightly covered with compost, for potting up a little later. Alternatively, pot each tuber up individually, in a large plastic pot filled with multi-purpose potting compost. Position the tuber the right way up (look for the old stem, or a new shoot – this is the top) and position it so that it sits just below the soil surface. Water in well, allowing any excess water to drain away.
Put the tubers in a light, frost-free place (such as a greenhouse, cold frame, porch or windowsill) and keep the compost moist. New shoots should start to form about five weeks after planting. They will have formed bushy plants by the time the frosts have ended in May.
How to plant dahlias
In mid to late May, once no more frosts are forecast, dahlias can be planted out into the garden. Before you do this, you may need to remove some shoots from the tuber, leaving around five remaining. It feels harsh, but it will encourage bushy plants that will produce lots of flowers. You can use any extra shoots to make basal cuttings – see below.
Harden off the plants before planting your dahlias outside – put them outside during the day but bring them back inside at night for a week or so.
Dig a planting hole that’s around 30cm across, and add a bucket full of well-rotted organic matter to increase soil fertility. If your soil is heavy clay, you could add some horticultural grit to the base of the planting hole, for drainage. Protect the new shoots from slugs and snails. If you’re planting a dahlia bought at the garden center, plant at the same depth they were in the pot.
Dahlias like plenty of room to grow – grow them around 60cm apart.
Once you’ve planted your dahlia, you will need to provide it with some support, unless its a dwarf variety. Dahlias grow fast and have a tendency to flop, especially if the flower heads are large. Add a stout stake or bamboo canes at all four corners (these will be hidden as the plant grows). Tie the new growth in every couple of weeks.
If you’re planting dahlias in a pot, choose a large container that’s at least 30cm wide and deep, and fill with multipurpose compost, mixed with organic matter such as well rotted manure. You could add some slow-release plant food at the same time. Plant at the same depth as they were in their original pot.