The Ultimate Guide to Planting Dahlia Tubers in New Zealand

Welcome to the ultimate guide on planting dahlia Tubers in New Zealand! Whether you're a seasoned gardener or a beginner with a green thumb, this comprehensive guide will equip you with everything you need to know to plant and grow these stunning flowers successfully.

Dahlias are popular with many garden enthusiasts because of their vibrant colours and intricate petal formations. However, to ensure a thriving garden, it's important to understand the specific requirements for growing dahlias in New Zealand's unique climate.

This guide will cover all the essential steps, from choosing the right dahlia Tubers to preparing the soil for planting. We'll delve into the ideal planting time, spacing, and watering techniques to maximise growth and blooming. Additionally, we'll share expert tips on preventing common pests and diseases that may affect your dahlia plants.

Whether you're planning to add dahlias to your existing garden or create a dedicated dahlia bed, this guide has got you covered. So, grab your gardening gloves and get ready to unleash the beauty of dahlias in your garden!

The History of Dahlia Tubers

In the distant past, precisely in the year 1789, a collection of Dahlia's journeyed from their native soil of Mexico to the esteemed botanical gardens of Madrid. Accompanying them was a suggestion to cultivate them for culinary purposes. However, this idea did not catch on at the time.

The Dahlia’s fate took a dramatic turn when Joséphine de Beauharnais, the esteemed spouse of Napoleon, took a fancy to these florals, deciding to adorn her entire garden with their presence. Her influence set a trend, and soon, Dahlias were the coveted addition to every garden. Their allure spread rapidly, making them accessible and affordable to all, shifting their status from rare luxuries to common favourites. For an extended period, the Dahlia endured this humble classification. But as time would have it, the Dahlia experienced a renaissance, regaining its esteemed position in the horticultural world. Once again, this floral gem has become a sought-after treasure in gardens everywhere!

Understanding Dahlia Tubers and their characteristics

Dahlia tubers are the underground storage structures that give rise to the beautiful dahlia plants we love. These tubers store nutrients and energy during the dormant period, allowing the plant to survive adverse conditions and bloom year after year.

When choosing Dahlia tubers, it's important to look for healthy specimens. Select Tubers that are firm, plump, and free from any signs of rot or damage. The size of the Tubers can vary depending on the variety, but larger tubers tend to produce more robust plants and blooms. Unlike the varieties you'll find in-store, our tubers at Bulbs Direct are never pre-packaged. Once we're ready to pack your order, we select the varieties you've chosen, bag them, and post them directly out to you.

Dahlia tubers come in a wide range of colours, sizes, and forms. From small pompon dahlias to dinner-plate-sized blooms, a dahlia variety suits every taste. When selecting your Tubers, consider the desired height, colour palette, and flower shape to create a well-balanced and visually appealing garden.

We're proud to be a reputable supplier and have been nuts about dahlias for yonks. We have a wide selection of varieties suited to New Zealand's climate - check out our gardener's guide for expert advice on cultivation and care for all the Tubers we stock.

Choosing the right location for planting Dahlia Tubers

Selecting the right location for planting your dahlia Tubers is crucial for their growth and overall health. Dahlias thrive in full sun, so choose a spot in your garden that receives at least 4 hours of direct sunlight each day.

Dahlias also require well-draining soil to prevent waterlogged roots, which can lead to rot and other diseases. If your garden soil is heavy or clay-like, consider amending it with organic matter such as compost or well-rotted manure to improve drainage.

When it comes to spacing, dahlias appreciate some elbow room. Give each dahlia plant enough space to spread out and grow to its full potential. The exact spacing will depend on the variety and mature size, so refer to our grower's guide for instructions on planting your dahlia Tubers.

Additionally, consider the height of your dahlia plants when choosing their location. Taller varieties may require staking or support structures to prevent them from toppling over in strong winds. Take this into account when planning your garden layout to ensure the best results.

Preparing the soil for Dahlia Tuber planting

Proper soil preparation before planting dahlia Tubers is essential for their long-term health and growth. Begin by clearing the area of any weeds, rocks, or debris that may hinder root development or cause competition for nutrients.

Next, use a garden fork or tiller to loosen the soil to a 20-30cm depth. This will create a well-aerated environment and allow the dahlia roots to penetrate easily.

Incorporate organic matter such as compost or well-rotted manure to improve soil fertility and drainage. Spread a layer of organic matter over the planting area and mix it into the soil using a rake or garden fork. Our Dahlia Fertiliser  has been specifically formulated for NZ soils - with all the goodness needed to get those Dahlias reaching their full potential

When and how to plant Dahlia Tubers in New Zealand

Now that you've chosen the perfect location and prepared the soil, it's time to plant your dahlia tubers. The best time to plant Dahlias here in NZ is October or November, but they can be planted anytime from mid-August through late December.

Dig a hole that's slightly larger than the tubers and deep enough to accommodate the entire root system. Generally, a hole depth of around 5-10cm should be sufficient. Place the Tubers in the hole with the concave side facing up and the eye, or bud, pointing upwards.

Cover the Tubers with soil, making sure they are completely buried, and gently firm the soil around them to provide support. Be careful not to damage the Tubers during this process, as any injuries can leave them vulnerable to disease or rot.

Space the Dahlia tubers around 50cm apart. This will ensure that each plant has enough room to grow and receive adequate sunlight and nutrients. Water well and keep moist, being careful not to over-water.

Caring for Dahlia Tubers during the growing season

Once your dahlia Tubers are planted, proper care during the growing season is crucial for their development and blooming. Here are some key considerations to keep in mind:

Watering: Dahlias require regular watering, especially during dry periods. Aim to keep the soil evenly moist but not waterlogged, as excessive moisture can lead to root rot. Water deeply to encourage deep root growth, and avoid watering the foliage to minimise the risk of fungal diseases.

Fertilisation: Dahlias are heavy feeders and benefit from regular fertilisation. Apply our Dahlia Fertiliser when planting, and follow up with additional applications every 4 to 6 weeks throughout the growing season. This will ensure a steady supply of nutrients for healthy growth and abundant flowering.

Shoot Removal: It's often recommended to remove all but five shoots sprouting from the tuber. There may be several more shoots, some of them spindly, but all but five should go. This will encourage bushy, vigorous plant growth with masses of blooms.

Weeding: Keep the area around your dahlia plants free from weeds, as they can compete for nutrients and water. Regularly remove any weeds by hand or use a shallow hoe to prevent them from taking hold and impacting the health of your dahlias.

Support: As your dahlia plants grow, taller varieties may require support to prevent them from toppling over in strong winds or heavy rain. Install stakes or a suitable support structure when the plants are young to avoid damaging the roots later on.

Deadheading: Deadheading prolongs the flowering season. To encourage abundant blooms in your Dahlias, pinch out the tops of your Dahlia plants after the second set of leaves has developed. It might sound ruthless, but the results are worth it! By doing this, your Dahlia plant will produce four flower stalks instead of one. This ensures a delightful display of blooms for weeks, even months to come! You can either cut off the tops with a sharp knife or squeeze between your thumb and forefinger, removing the main shoot down to the top two pairs of leaves

Mulching: Applying a layer of organic mulch around your dahlia plants can help conserve moisture, suppress weeds, and regulate soil temperature. Use a nice layer of mulch, such as straw or wood chips, being careful to keep it away from the plant's stem to prevent rot.

Following these care guidelines will give your dahlia Tubers the best conditions for healthy growth and a stunning display of blooms.

Common pests and diseases affecting Dahlia Tubers

While dahlias are generally hardy and resilient plants, they can still fall victim to a few common pests and diseases. Here are some of the most prevalent issues you may encounter and how to address them:

Aphids: These small, soft-bodied insects can cluster on the undersides of leaves, causing stunted growth and distorted foliage. Control aphids by spraying the affected plants with a strong stream of water or using our amazing Natural Insecticide, taking care to target the insects directly.

Slugs and Snails: These slimy creatures can chew on the leaves and stems of dahlia plants, leaving ragged holes and causing cosmetic damage. Reduce slug and snail populations by removing hiding places like garden debris and employing organic controls like copper tape or beer traps.

Powdery Mildew: Powdery mildew appears as a white, powdery coating on the leaves and stems of dahlia plants, often in humid conditions. Improve air circulation by providing adequate spacing between plants and avoiding overhead watering. Fungicides may be necessary in severe cases.

Botrytis Blight: Also known as grey mould, botrytis blight can cause wilting, rotting, and browning of dahlia flowers and foliage.

Root Rot: Excessive moisture or poorly draining soil can lead to root rot, causing yellowing leaves, wilting, and plant death. Improve drainage by amending the soil with organic matter and avoiding overwatering. Fungicides may be necessary in severe cases, but prevention is key.

Regular monitoring and prompt action are key to managing pests and diseases in your dahlia garden. By staying vigilant and implementing appropriate control measures, you can minimise the impact of these common issues and ensure the health and vitality of your plants.

Picking Dahlias

Unlike many flowering tubers, Dahlia flowers do not continue to open after they’ve been cut. Therefore, selecting blooms that are fully open when picking them is crucial.

If you can’t gather every bloom for your vase, consider having an occasional deadheading session. This practice not only keeps the plant tidy but also significantly extends its flowering period, ensuring that more nutrients are directed toward the production of healthy tubers.

Harvesting and storing Dahlia Tubers

As the end of the growing season approaches, it's time to prepare your dahlia Tubers for winter storage. Dahlias are not winter-hardy, so lifting the Tubers before the first frost is important if you live in some of New Zealand’s colder climates is important.

To harvest your dahlia Tubers:

  1. Carefully dig around the plant using a garden fork or shovel, taking care not to damage the tubers.
  2. Lift the plant from the ground and gently shake off excess soil
  3. Trim the foliage back to about 6 inches
  4. Allow the Tubers to air dry in a well-ventilated area for a few days or until the soil has completely dried
  5. Once dry, gently brush off any remaining soil and inspect the Tubers for any signs of damage or disease
  6. Discard any Tubers that are soft, mushy, or show signs of rot
  7. Choose a cool, dark, and dry location such as a basement or garage to store your Dahlia Tubers over winter. 
  8. Place the Tubers in a shallow container or crate filled with dry peat moss, vermiculite, or sawdust. Tip: To prevent the spread of disease, make sure the tubers do not touch each other.
  9. Check on the Tubers periodically during storage to ensure they remain firm and free from rot. If any Tubers show signs of deterioration, remove them immediately to prevent further spread.
  10. In early spring, as the risk of frost subsides and the soil warms up, you can replant your stored dahlia Tubers following the same guidelines outlined earlier in this guide. 

With proper care and storage, your dahlia Tubers will be ready to dazzle your garden once again.

Tips for successful Dahlia Tubers planting in New Zealand

To recap, here are some additional tips to ensure successful dahlia Tubers planting in New Zealand:

  1. Choose healthy dahlia tubers from reputable suppliers or nurseries specialising in dahlias.
  2. Select a sunny location with well-draining soil for optimal growth and blooming.
  3. Prepare the soil by removing weeds and incorporating organic matter to improve fertility and drainage.
  4. Plant dahlia tubers in early spring, once all risk of frost has passed and the soil has warmed up.
  5. Provide regular watering, fertilisation, and support for your dahlia plants during the growing season.
  6. Stay vigilant for common pests and diseases, and take appropriate measures to control and prevent them.
  7. If you live in a cold climate, harvest and store dahlia Tubers before the first frost, keeping them in a cool, dark, and dry location.
  8. Replant stored dahlia Tubers in early spring for another season of beautiful blooms.

By following these tips and guidelines, you'll be well on your way to a thriving dahlia garden in New Zealand.


Dahlias are a stunning addition to any garden, and with the right knowledge and care, you can enjoy their vibrant colours and intricate blooms year after year. From understanding the characteristics of dahlia tubers to choosing the right location, preparing the soil, and caring for your plants throughout the growing season, this guide has provided you with all the information you need to plant dahlia tubers successfully.

Remember to stay vigilant for common pests and diseases and take appropriate measures to address them promptly. When the growing season ends and you live in a cold climate, be sure to harvest and store your dahlia tubers properly to ensure their survival through the winter months.

So, grab your gardening gloves, prepare your soil, and get ready to unleash the beauty of Dahlias in your New Zealand garden. With a little bit of effort and a lot of love, you'll be rewarded with stunning blooms that will brighten your days and bring joy to your garden. 

Happy planting!

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