DAHLIA QUICK START CHECKLIST
- Pick your variety: choose from a rainbow of colours and forms - dahlias offer endless options.
- Plant in the right spot: Dahlias thrive in full sun, in a sheltered spot with well-drained soil.
- Prepare the soil well with organic matter like Tui Compost and Tui Organic Sheep Pellets. Plant into a specialty mix like Tui Rose & Shrub Mix.
- Feed regularly: keep feeding your dahlias for vibrant blooms. Choose the fertiliser option that best suits how you want to garden, for quick visible results try Tui All Purpose Liquid Superfood.
- Water and deadhead: keep soil moist and remove spent flowers regularly to extend the season.
CHOOSE YOUR DAHLIA
Dahlias are one of the most rewarding flowers to grow, offering vibrant colour and long-lasting blooms. There are two types of dahlias, bedding dahlias grown from seed and dahlia tubers - tubers are a type of bulb and are the most common way to grow dahlias.
There’s a dahlia for every garden! There are so many varieties to choose from, including pompom, dinner plate, cactus and ball flower types, that come in colours from white to blush pink to intense burgundy red, as well as bicolour options with flecks and stripes for something different. Consider the size your dahlia will grow to – most will need staking.
Some favourite varieties to look out for are Cafe au Lait, Cornel Bronze, Labrinth, Sweet Nathalie, Wizard of Oz, Petra’s Wedding, Caitlin’s Joy, Coralie, Kotare Buttermilk, Wine Eyed Jill, Break Out, Ivanetti, Rocco and Copper Boy.
When purchasing tubers check that the tuber has a body (the swollen bulb) a neck (the skinny piece) and crown with at least one eye - this is where the shoots will emerge from.
They thrive in full sun and tolerate a range of soil types, as long as it’s fertile and well-draining. If you’re in a frost-prone area, wait until the last frost has passed before planting - new growth is delicate and won’t survive cold snaps.
PREPARE THE SOIL
- Plant in spring, usually October onwards when the risk of frost has passed.
- In frost prone areas dahlia tubers can be potted up and grown on until it is safe to plant out in the garden. In frost free regions you can plant in spring as soon as the tubers are available or are starting to sprout in storage.
- Dahlias love moist, fertile, free draining soil – the tubers will rot in heavy, poorly drained soils.
- Dig in organic matter such as Tui Compost and Tui Sheep Pellets to enrich your soil. Then add a layer of Tui Rose & Shrub Mix to plant into.
GET PLANTING
Planting dahlia tubers in the garden
- If planting in the same bed, space tubers 20-30cm apart to ensure there is good air circulation around plants.
- Dig a hole 10-15cm deep and lay the tuber on its side with a growing eye pointing upwards.
- Cover with Tui Rose & Shrub Mix and firm down.
- Water well when you plant them, but don’t water again until there is at least 5-10cm of new growth. Dahlias are susceptible to soft rot, so overwatering at this stage (before they’ve grown roots) will lead to tubers rotting.
- Add stakes at the time of planting time to avoid damaging tubers later, this helps mark there the tubers are.
- Gradually increase watering as your dahlia plants grow.
Planting dahlia tubers in pots
- Choose a pot or container at least 30L in size.
- Half fill the pot with Tui Rose & Shrub Mix.
- Lay the tuber on its side with an eye facing upwards and fill the pot to approximately 3cm from the top of the pot to allow for watering.
- You shouldn’t need to water until shoots appear. Once shoots appear, mist or dampen the soil around the new growth to keep it moist, don’t drench. You can gradually start increasing watering once there is at least 5-10cm of new growth.
Planting dahlias seedlings
- Plant seedlings in the early morning or late afternoon to avoid transplant shock.
- To reduce transplant shock, soak the seedlings in Tui Organic Seaweed Plant Tonic and allow to drain.
- If you’re planting in the garden add a layer of Tui Rose & Shrub Mix.
- If you’re planting in pots and containers, make sure it is no smaller than 30L and half fill with Tui Rose & Shrub Mix.
- Dig a hole slightly bigger than the root ball, then place seedling into the planting hole and fill around it.
- Add stakes at the time of planting if required, water well and maintain regular watering.
FEED AND NOURISH
- Once plants are approximately 50-100cm high you can start watering weekly, depending upon the weather. Deep watering is better than light sprinkles of water, at least 5-10 litres per watering. If leaves start to droop you can increase watering frequency, but avoid overdoing it as dahlias are susceptible to soft rot.
- Water the soil around plants, avoiding overhead watering as this can lead to disease problems such as powdery mildew.
- Feed your dahlias and they will reward you with a gorgeous summer show. Replenishing the nutrients used by your plants ensures your plants grow to their full potential.
- Choose from a variety of different Tui fertiliser options, depending on what suits you and your garden.
- As flower buds appear, start feeding dahlias planted in garden beds with Tui Bulb Food every 4-6 weeks. This fertiliser is lower in nitrogen, to encourage flowering rather than leafy growth.
- Tui Enrich Rose, Camellia, Azalea & Gardenia controlled release fertiliser lasts up to six months, making it perfect for gardeners who prefer a ‘feed and forget’ option. It’s also suitable for pots and containers.
- Tui All Purpose Liquid Superfood is perfect for quick results as plants can absorb the nutrients immediately. Suitable for dahlias growing in pots and containers or in the garden. For best results feed weekly from spring through to autumn until flowering has finished.
- Protect new shoots from slugs and snails by applying Tui Quash.
- Mulch around your dahlia plants with Tui Mulch & Feed while there is still moisture in the soil in late spring, early summer. This will help to conserve soil moisture, prevent roots from drying out, and keep the soil free of weeds.
- Deadheading will prolong flowering. Let foliage die down naturally at the end of the season before tidying up.
- To protect tubers in frost-prone areas or poorly drained soil, dig them up in winter and store in a cool, dry place. Label them for easy replanting in spring.
FREQUENTLY ASKED QUESTIONS
When is the best time to plant dahlias in New Zealand?
- The ideal time to plant dahlias is in spring, once the danger of frost has passed - typically around Labour Day weekend (late October).
- Dahlias are frost-sensitive, so planting too early can damage young shoots.
- In frost free-regions dahlias can be planted in spring, from September onwards.
- For best results, plant tubers directly into well-drained soil in a sunny spot, or start them in pots indoors to get a head start.
Do dahlias grow well in pots?
- Dahlias can thrive in pots if given the right conditions.
- Choose a large container - at least 30 litres - to allow room for tuber growth and root development.
- Use a specialty planting mix like Tui Rose & Shrub Mix, which provides essential nutrients and good drainage.
- Place the pot in a sunny location, water regularly, and feed with a liquid fertiliser every few weeks.
- Compact varieties or dwarf dahlias are especially well-suited to container growing.
Why aren’t my dahlias flowering?
- If your dahlias aren’t blooming, there could be several causes:
- Insufficient sunlight: Dahlias need at least 6 hours of direct sun daily.
- Poor soil nutrition: Feed with a balanced fertiliser in spring and again in mid-season.
- Overcrowding: Plants spaced too closely compete for nutrients and light.
- Excess nitrogen: Too much nitrogen encourages leafy growth at the expense of flowers.
- Lack of deadheading: Removing spent blooms encourages new buds to form.
- To boost flowering, ensure your dahlias are planted in fertile, well-drained soil, spaced correctly, and fed regularly with a suitable fertiliser.
Should I dig up dahlia tubers in winter?
- In frost-prone regions or gardens with heavy, wet soil, lifting dahlia tubers in winter is recommended.
- After the first frost blackens the foliage, cut back the stems and gently dig up the tubers.
- Brush off excess soil and store them in a cool, dry, and dark place - like a garage or shed - in sawdust, newspaper, or dry potting mix.
- Label each tuber to keep track of varieties.
- In milder climates with well-drained soil, tubers can be left in the ground, but mulching for protection is recommended.
Discover more advice and inspiration for growing beautiful bulbs at the Bulb Hub >