Dahlias are the stars of the summer and autumn garden — bold, beautiful, and endlessly diverse. Whether you’re drawn to the dreamy pastels of café-au-laits or the structured drama of a cactus-flowered variety, dahlias bring colour, form, and joy to every garden style.
At Sharon Harris Garden Design, we work with dahlias both as a design feature and as a beloved garden staple — and we want to help you grow them successfully, from tuber to bloom.
Dahlia tubers are best planted in spring, once the risk of frost has passed. In most parts of Victoria, this is from late September to November. They need warmth to get going and won’t thrive in cold, wet soil.
To plant:
Choose a sunny, well-drained spot.
Dig a hole about 10–15 cm deep.
Lay the tuber horizontally, with any visible “eyes” or shoots facing up.
Cover with soil, but hold off watering until green growth appears above the surface (to avoid rot).
Space plants about 60 cm apart, depending on variety.
If your garden is prone to frost, you can start dahlias in pots under cover and plant them out once the weather warms.
Dahlias thrive in full sun — at least 6 hours of direct sunlight daily. Morning sun with some afternoon shade is ideal in hot inland gardens.
They prefer:
Rich, free-draining soil (a loamy mix with plenty of organic matter)
Neutral to slightly acidic pH
A position sheltered from strong winds — they can get top-heavy and snap easily if not supported
Before planting, dig in compost, well-rotted manure, or blood and bone to nourish the soil and support vigorous growth.
Dahlias are relatively low-maintenance but hungry and thirsty during their growing season.
Water deeply 2–3 times a week once they’re established
Avoid wetting the foliage to help prevent mildew
Mulch lightly to conserve moisture and reduce weed competition
For best blooms, feed every 2–3 weeks with a balanced fertiliser, switching to a low-nitrogen mix once buds appear to encourage flowers over foliage.
Many dahlia varieties grow tall and need support.
Insert stakes or frames at planting time to avoid damaging the tuber later
Tie stems loosely with soft garden ties as they grow
For bushier plants and more blooms, pinch out the growing tips when they reach about 30 cm tall
Deadheading is key to keeping dahlias blooming from mid-summer right through autumn.
Snip off spent blooms just above a leaf joint
Remove any weak or damaged stems
Check regularly for snails, earwigs, or aphids
In colder climates or heavy soils, it’s safest to lift and store tubers over winter. After the first frost:
Cut back foliage to about 10 cm.
Gently dig up the tubers and allow them to dry.
Store them in a cool, dry, frost-free place, in slightly damp sawdust, vermiculite, or coco coir.
Label them carefully!
In milder areas with good drainage, you can leave tubers in the ground, adding a thick mulch layer for protection.
Dahlias are a dream to design with. Their bold shapes and wide colour palette make them ideal for:
Seasonal feature beds
Cutting gardens
Meadow-style borders
Pairing with grasses, salvias, cosmos, rudbeckia, and perennials
We love using dahlias to create focal points and late-season colour that carries the garden through to the first frost.
Whether you’re dreaming of a statement bed of giant dinner-plates or a soft, romantic mix for your borders, Sharon can help you select varieties to suit your climate, soil, and style.
Get in touch to book a garden consultation or seasonal planting plan. Call Sharon on 0413 232 009 or email : sharon@shgardendesign.com.au
Yes — especially dwarf or medium-sized varieties. Use large pots (at least 40 cm wide), quality potting mix, and feed regularly.
With care and deadheading, dahlias will bloom from mid-summer right into late autumn.
Yes, but most dahlias are grown from tubers to preserve the flower form. Seed-grown dahlias are fun but more variable in result.
