How to Grow Dahlias - Growing Dahlias From Seed or Tubers

Dahlias come in a huge range of colours from bright whites and yellows to deep pinks, purples, reds, and more. With shapes aplenty, you can enjoy everything from cactus to anemone, single, collarette, decorative, ball and even Dahlia Pompon. 

Sizes are also bountiful and dahlias range from dwarf dahlias of 35cm high to trees towering well over 2 metres. Their flowers can reach the size of dinner plates and go all the way down to small delicate balls, so there are plenty of options available.

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

One of the most popular and spectacular perennial flower seeds you can grow at home, dahlias are easy to grow and reward you with abundant flowers throughout the warmer months. In this guide, we’ll discuss when to plant dahlias in Australia, how to grow dahlias from seed, and how to plant dahlia tubers, giving you everything you need to know to grow these show-stoppers in your garden!

• Growing Dahlias from Seed vs Tubers
• Cost
• True to Type
• Flowering Performance
• Where and When to Grow Dahlias in Australia
• Climate
• Position
• Soil 
• Water
• How to Grow Dahlias from Seed
• Soil Preparation 
• Sowing
• Planting
• Plant Care
• Harvesting
• How to Grow Dahlias from Tubers
• Ground Preparation 
• Planting
• Plant Care
• Harvesting
• Harvesting Dahlia Flowers
• Buy Dahlia Flowers

Growing Dahlias from Seed vs Tubers

Dahlias are commonly grown from tubers (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 an average of $5 for 50 seeds whereas a dahlia bulb will cost you around $9-17 per bulb. So, if you’re watching the pennies, it’s a bit of a no-brainer. 

True to Type

As you might expect, growing dahlias from seed is very different to growing from a tuber. 

To start, a dahlia tuber is harvested from a parent plant so will be identical to its parent. Because of this, you’ll know the exact colour and style you’ll end up with when planting dahlias from tubers. Propagating from seed, however, results in a random specimen based on the genetics of the seed and insect pollination, which modifies its genetic makeup. As a result, you won’t know the colour or size of your dahlias until they flower. 

This may be exciting for people who love surprises, but if you want a specific variety or have a purpose for your dahlias, you’re better off growing from tubers.

Flowering Performance

Dahlias grown from seed or tubers result in a flowering plant in their first year. However, as tubers store more energy than seeds, you’re more likely to see longer and better flowering in year one. Seed-grown dahlias, on the other hand, will develop tubers as they grow and become stronger as the years go on.

Where and When to Plant Dahlias in Australia

Whether growing dahlias from seed or learning how to grow dahlias from tubers, it’s important to understand where and when to plant dahlias in Australia. Let’s explore some of the key factors that play a part. 

Climate

Dahlias can grow in most climates within Australia but prefer warmer areas because they don’t handle frost well. So, you should plant dahlia seeds after the risk of frost has passed. 

Dahlia tubers handle living in well-draining soil throughout their dormancy, but if you experience cold winters or your soil is prone to waterlogging, you may be better off digging up your tubers at the end of the growing season and storing them in a cool, dry place until next year.

Position

Dahlias are sun lovers, so they will flower best when 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 is ideal for growing dahlias from seed and you should mulch to keep weeds at bay and keep soil cool in summer. Dahlias are resilient and will grow in suboptimal soils such as heavy clay, but don't expect a strong performance.

Water

Dahlias are quite drought-resistant once established, but keep them well-watered and fed regularly throughout the flowering season for best performance.

How to Grow Dahlias From Seed

Growing dahlias from seed is easy if you know what you’re doing, so let’s lay the groundwork. 

Soil Preparation

Dahlia seedlings are best planted in the garden after the last frost date and can be started early indoors. This gives you lots of options compared to many other flowers.

Sowing Your Dahlias From Seed

Ready, set, sow! Specifically, sow seeds 5mm deep in seed-raising mix and keep them nice and moist. If you are sowing in spring or summer, you can do so directly into their final growing position in the garden if preferred. If you’ve played your cards right, your dahlia seedlings should appear in 10-14 days.

Planting Dahlias From Seed

Transplant your dahlias into a sunny part of the garden when they’re large enough to handle and the danger of frost has passed. But don’t just put them anywhere! Instead, plant them in well-draining soil enriched with organic matter and rotted manure.

Caring for Dahlias when Growing From Seed

Start your care routine by mulching around the dahlia seedlings. This keeps weeds at bay and keeps the soil cool in summer. You should feed your dahlias with a liquid fertiliser when buds appear, then stake them as required. Oh, and don’t forget to protect them from the wind to avoid stem damage!

If you follow these steps, your flowers should appear about 3-4 months after germination.

Harvesting your Dahlias From Seed

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 the ones you’ve just grown, so essentially, you will create your own unique variety of Dahlia! 

At the end of the growing season let your dahlia plants die back before cutting them off at ground level. This will allow energy to return to the tuber, energising it for a bigger and better flowering season next year.

How to Plant Dahlia Tubers

Wondering how to plant dahlia tubers as opposed to growing dahlias from seed? We’ve got you covered with four easy-to-follow steps. 

Soil Preparation

Before you begin, prepare a wide planting hole at least 30cm deep. Half-fill your hole with rich organic matter and rotted manure, and dig in some blood and bone. 

Planting Your Dahlias from Tubers

Next, plant your tuber about 10-15cm deep and 30cm apart. Dahlias are big-time sun worshippers so let them sunbathe in full sun instead of in shady conditions. 

Caring for Your Dahlias from Tubers

Mulch around the base to keep weeds at bay and to keep the soil cool in summer. In addition, feed them with a liquid fertiliser when their buds appear, and regularly throughout the growing season. You should also stake as required and protect them from wind as this may damage their stems. Dahlias will bloom all summer when regularly fed and watered.

 

How to Harvest Dahlia Tubers

Regular harvesting of flowers and deadheading will result in more flower growth. At the end of the growing season let your dahlia plants die back before cutting off at ground level, this allows energy to return to the tuber, energising it for a bigger and better flowering season the next year!

If you wish to divide your tubers, you can lift them during dormancy and split them for planting the next year. Find out how to divide bulbs in our handy guide.

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?

Buy Dahlia Flower Seeds & Tubers at Mr Fothergill’s Seeds

Mr Fothergill's stocks a huge range of dahlia seeds and dahlia tubers with seeds available all year round and dahlia tubers available from August to September each year. For more information about what you can and can’t plant throughout the Australian calendar, head to our garden advice blog which is full to the brim with top tips and handy advice.