How to grow Dahlias from seed or tubers

July 28, 2022

How to grow Dahlias from seed or bulbs

Dahlias are one of the most popular and spectacular perennial Summer flowers you can grow at home. They are easy to grow and will reward you with an abundant show of flowers throughout the warmer months. Here are our tips on how to grow Dahlias from seed or tubers.

Dahlias come in a huge range of colours from bright whites and yellows to deep pinks, purples, reds, and everything in between. Their shapes and sizes are equally as varied with bloom shapes such as cactus, anemone, single, collarette, decorative, ball and pompon (pompom). Sizes also range from compact dwarf shrubs 35cm high to trees towering well over 2 metres.  Their flowers can reach the size of dinner plates right down to small delicate balls.

The various types of Dahlias

Dahlias come in a huge range of colours, shapes, and sizes


Seeds vs Tubers


Dahlias are most commonly grown from tubers (also known as bulbs) but can also be grown from seed. When deciding whether to grow Dahlias from seeds or tubers there are a few things to take into consideration:

Cost: A packet of Dahlia seeds will set you back on average $5 for 50 seeds meaning you get great bang for your buck. A Dahlia bulb will cost you around $9-17 per bulb depending on the variety.

True to type: Growing Dahlias from seed is very different from growing from a tuber. A Dahlia tuber is harvested off a parent plant meaning what you grow will be identical to that of the parent it was harvested from, this allows you to know exactly what colour and style you will end up with. Whereas propagating from seed results in a random specimen based on the genetics within the seed and pollination from insects which modify the genetic makeup of the seed. This means you won’t know what colour or size your dahlias will end up being until they have flowered, whilst this may be exciting for some, if you are wanting a specific variety, you are better off growing from tubers.

Flowering performance: Dahlia’s grown from seed or tubers will both result in a flowering plant in the first year. However, as tubers store more energy than seeds, in the first year you are most likely to see longer and better flowering from a Dahlia grown from a tuber than that grown from seed. Seed-grown Dahlias will develop tubers as they grow and establish and will become stronger as the years go on.

 

How to Grow Dahlias from seed

Dahlia seedlings are best planted out in the garden after the last frost date but can be started early indoors.

  1. Sow seeds 5mm deep in seed raising mix and keep moist. If you are sowing in Spring or Summer, you can sow direct into their final growing position in the garden if preferred.
  2. Seedlings should appear in 10-14 days.
  3. Transplant into a sunny part of the garden when large enough to handle and the danger of frost has passed. Plant into well-draining soil enriched with organic matter and rotted manure.
  4. Mulch around your seedlings to keep weeds at bay and keep the soil cool in Summer.
  5. Feed with a liquid fertiliser when buds appear.
  6. Stake as required and protect from wind as this may damage their stems.
  7. Flowers should appear approximately 3-4 months after germination.
  8. At the end of the growing season allow your Dahlia plants to die back before cutting off at ground level, this will allow energy to return to the tuber, energising it for a bigger and better flowering season the next year!
  9. Your Dahlia plants grown from seed will produce tubers, which once mature can be lifted and separated at the end of the growing season. These tubers will grow identical flowers to what that plant produced. Essentially, you have just created your own unique variety of Dahlia!

 

How to grow Dahlias from tubers/bulbs

  1. Prepare a wide planting hole at least 30cm deep, half fill with rich organic matter and rotted manure, dig in some blood and bone prior to planting. Plant your tuber around 10-15cm deep and 30cm apart in full sun.
  2. Mulch to keep weeds at bay and keep the soil cool in Summer.
  3. Feed with a liquid fertiliser when buds appear and regularly throughout the growing season.
  4. Stake as required and protect from wind as this may damage their stems.
  5. Dahlias will bloom all Summer when regularly fed and watered.
  6. Regular harvesting of flowers and deadheading will result in more flower growth.
  7. At the end of the growing season allow your Dahlia plants to die back before cutting off at ground level, this will allow energy to return to the tuber, energising it for a bigger and better flowering season the next year!
  8. If you wish to divide your tubers, you can lift them up during dormancy and split them ready for planting the next year.

Where can you grow Dahlias?


Climate
: Dahlias can grow in most climates within Australia but prefer warm areas. They do not handle frost well so plant after the risk of frost has passed. Dahlia tubers can handle living in well-draining soil throughout their dormancy. If your Winters are particularly cold or your soil is prone to getting waterlogged, you may be better off digging up your tubers at the end of the growing season and storing them in a cool, dry place for the next year.

Position: Dahlias are sun lovers, so they will flower best where they receive at least 6 hours of sun. Morning sun is best, and a sheltered position away from strong winds will help protect their stems from breakages.

Soil: Well-draining, rich, fertile soil will see your Dahlias thrive. Mulch to keep weeds at bay and to keep the soil cool in Summer. Dahlias are pretty resilient so will also grow in suboptimal soils such as heavy clay, but don't expect as good a performance.

Water: Dahlias are quite drought resistant once established. Keep well-watered and feed regularly throughout the flowering season for best performance.

 

How to harvest Dahlia flowers?


Dahlias are best cut as soon as the blossoms open and preferably in the cool of the early morning. Cut using secateurs and place straight into a vase of tepid water.

Dahlias make excellent cut flowers and last well in vases. They are also very popular competition flowers, so why not look at entering your blooms in your local agricultural or flower show?

 

Mr Fothergill's stocks a huge range of Dahlia seeds and Dahlia tubers. Dahlia seeds are available all year round, whilst Dahlia Tubers are available August to September each year.

Shop the range here.

 

Dahlia colours and varieties

More Dahlia colours and varieties