How to Grow and Care for Dahlias

Dahlias produce colourful blooms throughout summer and well into autumn in Australia. Their flowers can be big and blousy or small and dainty - there are many different varieties to choose from with different colours, shapes and styles of flowers.

You can also choose dahlias based on their mature plant height. Compact or bedding varieties will only grow to around 30cm tall and are perfect for pots. While tall growing varieties can reach up to 2 metres and they’ll need stakes for support.

Dahlias prefer to grow in warm temperate climates but will grow in most areas so long as the risk of frost has passed.

Each year dahlia plants produce a cluster of new tubers - lifting and dividing these tuber clumps each year will improve the size and quality of your dahlia blooms. It’s also an easy way to increase the number of dahlia plants in your garden or share excess tubers with friends.

5 Steps to Growing Dahlias

Dahlias need a full sun spot, with some protection from hot afternoon sun and wind on extreme heat days
Dahlias love growing in Scotts Osmocote Premium Plus Superior Potting Mix or a free draining soil with plenty of Scotts Osmocote Compost Premium Soil Improver added
Dahlias are most commonly grown from dormant tubers or seeds but you can also find potted plants at your local nursery or garden centre
Many dahlia varieties grow tall - tall growing varieties will need staking or supports
Dig up dahlia tubers and divide them between Autumn or Winter. Store divided tubers in a dark and dry place ready for re-planting in Spring

Preparation & Planting in the Garden

Dahlias need to be planted in a full sun spot, with free draining soil. Dahlias will appreciate protection from extremely hot afternoon sun and strong winds.

Prepare the soil before planting by mixing Scotts Osmocote Compost Premium Soil Improver through the top 10-20cm of soil.

Planting dahlia tubers

Dahlia tubers should be planted out in Spring once the risk of frost has passed. Plant tubers 10cm deep with any sprouting eyes facing up. Add a tall stake with the variety of name written on the stake at the time of planting if needed.

Protect the young sprouting dahlia leaves from slugs and snails by using beer traps (saucers filled with beer placed on the ground) or sprinkle some Defender Slug & Snail Pellets around each plant.

Planting potted dahlias

Plant potted dahlias into Scotts Osmocote Bulb Potting Mix or in prepared free-draining soil with compost Remove the dahlia from the nursery pot and gently tease the roots if they are really compact. Plant dahlias into the prepared soil and backfill around the plant. Water in well and protect new shoots from slugs and snails with beer traps or Defender Slug & Snail pellets.

Planting dahlia seeds

Plant dahlia seeds 1cm deep into pots filled with Scotts Osmocote Premium Plus Superior Potting Mix, lightly cover the seeds and keep them lightly moist while they germinate.

Once the seedlings have 2-3 sets of leaves they can be transplanted into larger pots. If planting into the garden follow the steps above for planting potted dahlias.

Planting in Pots

If you want to grow dahlias in pots, look for medium to large pots or planters with good drainage - choose a pot that is at least 30cm deep and about the same width.

Fill your pot or planter with Scotts Osmocote Premium Plus Superior Potting Mix and plant a dahlia tuber, potted plant or seeds following the instructions above.

The best dahlias for pots are the bedding varieties or more compact varieties - look for this information on the label.

Fertilising & Plant Care

Once new shoots appear on young dahlia plants fertilise them with a dose of a potassium-rich fertiliser, like Scotts Osmocote All Purpose Controlled Release Fertiliser to encourage healthy growth and more blooms.

Dahlia tubers should be lifted and divided at the end of autumn or early winter each year. Cut down any foliage as it dies back at the end of Autumn. Carefully dig up the tuber clump and divide it into individual tubers making sure each tuber has a growth “eye”. Store these tubers in a dark and dry place over winter (a cardboard box filled with sawdust or shredded paper is ideal), ready for re-planting in Spring.

If your soil is very free draining you can lift, divide and immediately replant dahlia tubers in early spring each year.

Pests & Diseases

Keep slugs and snails from eating young dahlia foliage and flower buds by placing beer traps around plants or sprinkling Defender Slug & Snail pellets at the base of each plant.

Whitefly, aphids and scale can sometimes cause a problem on dahlias too - spray any infestations with Defender Pyrethrum Insect Spray if needed.