How to Plant Dahlias: A Simple Guide for Beginners

 I started growing Dahlias last year for the first time. I was always worried about the level of maintenance required by Dahlias thanks to my Grandmother - she was always rushing home to 'deadhead the Dahlias'. That seemed high maintenance to me. I was so wrong, the rewards are worth the little maintenance required.

Dahila - Gambia Jane. My first Dahlia. It was early to bloom and prolific

If you want bold, beautiful blooms in your garden, dahlias are an excellent choice! Known for their vibrant colours and stunning shapes, these flowers are surprisingly easy to grow. Below is a quick overview to get you started, followed by more detailed steps. 

How to Plant Dahlia Tubers

- Choose the right time: Plant in spring, after the last frost. 

- Pick a sunny spot: Dahlias love full sun (6-8 hours daily). 

- Prepare the soil: Loose, well-draining soil enriched with compost works best. 

- Plant tubers correctly: Place them 10-15 cm deep with the ‘eye’ or bud facing upwards. 

- Space them apart: Give each tuber about 30-60 cm of space, depending on the variety. 

- Water carefully: Water sparingly at first to prevent rot, increasing as growth appears. 

- Support tall varieties: Add stakes or cages when planting if needed. 

Now, let’s explore each of these steps in more detail to set you up for success. 

Dahlia - Helena

Step 1: Choose the Right Time 

Dahlias are sensitive to cold, so plant them after the last frost date in your area. In Australia, this means mid to late spring is perfect. And in my area in Victoria's Macedon Ranges I wait until last weekend of October (known as 'Cup Day', thanks to the Melbourne Cup holiday).

Professional growers often plant them earlier and utilise frost cloths etc, but I prefer to delaying until the soil is warm enough to encourage healthy growth (its also less work and there is no great difference in time to flower). 

Step 2: Pick the Perfect Spot 

Dahlias thrive in full sun—6 to 8 hours of direct light daily is ideal. If planted in partial shade, they might produce fewer blooms. I also found that those in shadier areas were the first to develop powdery mildew.

Choose a location protected from strong winds to keep the stems from breaking. (See tip 7) My beds are very exposed to wind, so I like to place a stake next to the dahlia tuber at planting. this doubles up as an opportunity to label the tuber (you'll thank me later).

Step 3: Prepare the Soil 

Well-draining soil is essential to avoid tuber rot. If your garden has heavy or clay soil, mix in compost, sand, or aged manure to loosen it up. (also see step 6) 

You may be interested in my easy no-dig video on planting Dahlia tubers

Step 4: Plant the Tubers  

- Dig a hole: 10-15 cm deep. 

- Place the tuber horizontally: Make sure the eye or bud (a small bump) is facing up. If there’s no visible bud, don’t worry—it will sprout soon. Although I tend to wait until I can definately see a sprout, that way I know that the tuber is viable.

- Backfill gently: Cover the tuber with soil, but avoid compacting it too tightly. 

Step 5: Give Them Space 

Different varieties need different spacing: 

- Small dahlias (up to 50 cm tall): Space 30 cm apart. 

- Large varieties (over 1 m tall): Space 50-60 cm apart. 

Proper spacing ensures airflow, reducing the risk of diseases like powdery mildew. 

With deadheading and flower harvesting, your Dahlias will branch out and take up a lot of space.

Dahlia - Juliette

Step 6: Water Sparingly at First 

After planting, water lightly to settle the soil. Don’t overwater initially—too much moisture can cause tubers to rot before they sprout. Once you see leaves emerge, you can water more deeply about once a week. 

Step 7: Support Tall Varieties Early 

Some dahlia varieties grow quite tall and may need support to stay upright. Adding stakes or plant cages when planting will help you avoid disturbing the roots later. Simply tie the stems loosely to the stake as the plant grows. 

Cafe au Lait Dahlia

That's it!

Bonus Tips 

Pinch the tips: Once your dahlias reach about 30 cm tall, pinch off the top leaves to encourage bushier growth and more blooms. 

And like my grandmother, make sure you:

Deadhead spent flowers: This helps redirect energy into producing new blooms, keeping your plants vibrant throughout the season. 

or cut flowers as they are opening and bring them inside to enjoy

Conclusion 

Planting dahlias may seem intimidating at first, but by following these simple steps, you’ll set yourself up for a garden full of gorgeous

flowers. With the right care, dahlias will reward you with vibrant blooms from midsummer to autumn.

Happy planting! 

Sarah