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How to Grow Dahlias in Australia | Ultimate Growing Guide

Dahlias are a great species of flowering plant that need little work but offer a lot of rewards. Part of the Asteraceae family, these extravagant flowering plants grow quickly and produce big, bulbous blooms that range in colour from pastels to bright and brilliant shades.

If you’re wondering how to grow dahlias, here is everything you need to know to cultivate, care for and grow dahlias at home. 

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What are Dahlias

How to Grow Dahlias

Dahlias are a great growing option for many growers because if offered the right conditions, they’ll produce incredible blooms year after year. 

Originating from central American regions like Mexico, Columbia and Guatemala, dahlias are fantastic pollinators, garden vocals points and can fit into a variety of different spaces. 

With over a thousand different dahlia species, it’s also pretty easy to find a species that will suit your needs. Smaller dwarf varieties are great for bedding.

Compact, smaller-growing dahlias are perfect for pots. If you’re looking for a real statement piece, larger growing species like the imperialis can grow as much as 5 metres tall. 

What Types of Dahlias Are The Best to Grow? 

Types of Dahlias to Grow
  • Single Dahlias. This variety has a simple, single petal ring that forms in a circle. The most popular versions include ‘Joe Swifil’ or the ‘Bishop of York’.
  • Cactus Dahlias. This variety has a double petal bloom and is known to be bright and long-lasting. Popular varieties include ‘Doris Day’ or ‘Ryecroft Pixie’. 
  • Ball Dahlias. This dahlia variety has curved petals, which grow into a round sphere. Popular varieties ‘Jamanda’ or ‘Aurora’s Kiss’. 
  • Pompom Dahlia. Pompom Dahlias grow into perfectly round spheres. Popular varieties include the ‘Franz Kafka’ or ‘Moor Place’. 
  • Waterlily Dahlia. Much like the name, this variety produces saucer-like blooms. Popular varieties include ‘Kilburn Rose’ or ‘Taratahi Ruby’. 
  • Annemarie Dahlia. This variety has an unusual floral pattern. The most popular variety is the ‘Lambada’.
  • Decorative Dahlia. This variety has the largest growing blooms, with very intricate petals. The most common include the ‘Checkers’ or ‘David Howard’ variety. 
  • Colette Dahlia. This variety has a range of larger petals, which circle around a range of smaller petals. Popular varieties include ‘Chimborazo’ or ‘Yankee Doodle Dandy’.

How to Grow Dahlias

Caring for Dahlias

Dahlias are best grown from tubers, which many gardeners keep during the winter, to be replanted during the spring. However, these tubers can also be bought from your local garden centre at the start of spring. 

Dahlias are a plant that enjoy warm and sunny conditions, which is why it’s so important to remove them from your garden to over-winter them. Luckily, they can be replanted year after year if over-wintered correctly. 

When planting, it’s important to choose a sheltered, sunny spot with plenty of moist but well-draining soil. A south or west-facing spot is ideal. Soil can also be supplemented with a little bit of manure of organic matter to support your young dahlia plants. 

Before planting, it’s a good idea to acclimate your plants first. Keep your tubers near the spot of planting for one or two days prior. 

How Do You Plant Dahlias?

Dahlias need lots of space to grow. While the tubers may initially look quite small, they grow exponentially once they really get going. 

When growing in the ground: 

  • Dig a 30 centimetres wide hole into the ground. 
  • Using a garden fork, loosen the soil around the hole to make it easier for roots to expand. 
  • Pour a bucket of water mixed with compost into the hole, and then place it in your tubers. 

Be sure to grow tubers a minimum of 60 centimetres apart. 

When growing in a pot: 

  • Be sure to choose a big enough pot that is a minimum of 30 centimetres wide and deep. 
  • Choose a rich potting medium that is supported with some compost or manure.
Dahlias are a plant that enjoy warm and sunny conditions, which is why it’s so important to remove them from your garden to over-winter them

How Quickly Do Dahlias Multiply? 

Dahlia tubers begin to produce 5 to 6 new, strong shoots within the first two to three weeks of planting. 

You then have the option to leave each stem to grow into a large dahlia plant or to use a method of tubular division to propagate new plants. Division should be done using a sharp, sterilized knife. Take extreme care to divide each of the shoots, keep some of the tubes intact, and have as many roots per shoot as possible. 

The divisions can then be planted into some shallow compost to root. Once new growth appears, they can be replanted as above.

Caring for Dahlias

Dahlias grow incredibly fast and may sometimes need a little extra support. For larger growing varieties, it may be a good idea to stake weaker shoots, especially as they begin to produce large and heavy bulbs. 

Unless it’s a very rainy season, Dahlias will require a lot of additional water. They like the soil moist but not water-logged. So, take the time to regularly check your soil, especially growing in the ground. 

Although not always necessary, it can be beneficial to feed your dahlias every other week. Most gardeners recommend using a high potassium fertilizer, like tomato feed. 

Deadheading your dahlias is also recommended to promote more flowers. When deadheading, take extreme care to only cut back spent flowers and not new buds. These can be quite easily mistaken. 

How to Plant Dahlias

What About Overwintering? 

Unfortunately, dahlias rarely survive the winter if left outdoors, even in areas like Australia, where the winters can be slightly milder. Any form of frost may kill off your bulb and result in stunted growth for the following year. 

This is why many gardeners recommend removing your dahlias during the winter. You will need to: 

  • Cut the stems to approximately 12 cm tall.
  • Using a gardening fork, loosen the soil around the base of your dahlias. 
  • Using your hands, gently pull the tubular from the soil and dust off gently. 
  • Cover your tubulars in some newspaper and allow them to dry out for a few days.

You can keep your tubulars in some soil or compost, or even just a bag over winter. It is important, however, that you keep your tubulars away from any light or soil over the winter. 

A dark room shed, or dark spot in your greenhouse can work well.

Potential Dahlia Problems

The biggest issue many growers have are with slugs and snails. Snails and slugs absolutely love to feast on young dahlia plants. Luckily, you can control the presence of snails with slug pellets or a large copper ring around the base of your dahlia plant. 

Earwigs are another common issue, who tend to feast on the foliage of dahlia plants. To control earwigs, simply plant a stick or garden cane into the ground and place an upside-down garden pot on top. Earwigs will assemble inside the pot during the day, which enables you to quickly and easily dispose of them. 

How to Grow Dahlias Aussie Growing Guide

Final Dahlia Growing Tips

  • With so many varieties, it’s always a good idea to check the size and growing habits before purchasing your dahlia tubulars. 
  • If purchasing your tubulars from a garden centre, be sure to check the health first. Keep an eye out for any mould or rot. 

Wrapping Up Dalhia Growing Guide

So, there you have it. Everything you need to know about growing your very own dahlias at home: always be sure to give your dahlias as much sunlight as possible while keeping them in a semi-sheltered spot. 

Wherever you decide to grow your dahlias, whether in a pot, near your patio, by a pond or as a focal point in your garden, with just a little bit of work, you’ll be able to enjoy glorious blooms throughout the summer. 

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Gary Clarke

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