Dahlia
The dahlia is a very lovable flower that comes in many varieties of colours and shapes. It made its grand entrance in the early 1800s and is now found in every other garden around the world. The dahlia belongs to the Asteraceae family and today there are more than 50,000 registered varieties. In recent years, the popularity of dahlias has increased significantly and this number is expected to double in the coming years.
Besides being known for its fabulous appearance, the dahlia is especially popular as a cut flower. It’s a stunning showpiece flower that can enhance any summer bouquet with its varied appearance. It’s not for nothing that the dahlia is called the crown jewel of summer flowers! In this guide, you’ll find everything you need to know about growing dahlias and how to care for them.
How do i grow dahlias?
There are two ways to go when it comes to growing dahlia tubers, either you pre-cultivate them or you plant them directly on the site.
1. Pre-cultivation of dahlia tubers
If you want earlier flowering, we recommend pre-cultivating them sometime around March-April, depending on where you live. Start by spraying the tuber lightly with water/ or dip it quickly in water and then place it in a cultivation pot with a hole in the bottom. It is also possible to grow dahlias in plastic bags/freezer bags, which has become very popular as it takes up less space. The tuber should be planted about 10 cm below the soil surface in nutrient-rich potting soil and once planted, it wants to be in a bright and cool place.
Make sure to water very sparingly at first, until you see that the tuber has formed white suckers and green shoots have started to peek out of the soil. Dahlias are planted out after they have hardened off and when the risk of frost is completely over. A little tip is to also use a fibre cloth if there are slightly cooler nights to be on the safe side.
Step by step:
- Plant the tubers about 10 cm deep in a large pot of potting soil in March-April.
- Place in a warm spot and water sparingly until green shoots appear.
- When shoots appear, place in a bright and cool location
- After the last spring frost, acclimatise the plants to the outdoor climate by sheltering them during the day and bringing them inside at night.
TIP – Top your dahlias!
Dahlias can be topped when they are about 20 cm high. The stems will then branch out into dense, bushy plants. As a bonus, the cut off tops can be put in soil, and you will have even more dahlias. It is not certain that these cuttings will have time to form tubers during the summer. But there is a good chance that they will flower.
2. Direct planting
They can also be planted directly on the site, but it is important to keep an eye out for pests such as slugs, which can quickly munch on the small plants.
Step by step:
- Plant in a bed or pot outside in May-June when the risk of frost is low.
- Protect with fibre cloth or leaves on chilly nights.
Caring for dahlias – Watering and nutrition
Dahlias thrive best in a sunny position but can also thrive in partial shade. The most important thing is that they have plenty of room for their roots to grow and that the soil is nutritious. If the dahlia is to be planted in a pot, we recommend that it is at least 30 litres and preferably larger than that. Tall-growing varieties need plant support or tying up to prevent the stems from breaking Dahlias are very thirsty flowers that dry out easily and therefore require abundant but, most importantly, consistent watering. They also need a nutritional boost a few times during the season in order to continue to thrive and flower magnificently until the frost comes.
Dahlias are sumptuously beautiful in bouquets, so pick and enjoy. You can also cut off wilted flowers, known as deadheading. This stimulates the formation of new buds and prolongs flowering.
Deadheading
Regularly remove all faded dahlias to encourage the growth of new buds. This is also called deadheading and is essential if you want healthy plants with plenty of flowers.
Does the size and condition of the tuber matter?
Each dahlia tuber is unique, just like us humans. The appearance and characteristics of tubers can vary greatly between different varieties—in shape, size, and even traits such as growth time and productivity. Some have long, slender tubers, while others are short and thick. Certain varieties produce many tubers per plant, which can be divided multiple times, while others need to be propagated through cuttings as their tubers barely grow. Some dahlia varieties are also easy to store, whereas others are prone to rotting or drying out.
The appearance of dahlia tubers after winter storage can vary greatly between different varieties. Some shrivel significantly, while others retain more firmness, but in the end, they all produce large, beautiful plants with flowers. A tuber may look unappealing to the naked eye, but with the right conditions, the final result will still be the same. In other words, there is no standard condition or specific shape when it comes to dahlia tubers.
That’s why we always recommend planting the tuber before deciding that it’s unusable.
What can I plant together with dahlias?
Coriander, dill, giant verbena, and various types of poppies pair beautifully with dahlias. These plants bloom gracefully against the green foliage before the dahlias themselves start flowering.
What kind of nutrients do dahlias need?
Since dahlias require a lot of nutrients, it’s important to give them the best possible start by enriching the soil with slow-release chicken manure when planting. Another option is to mix cow manure into the soil.
During the growing season, dahlias need a few nutrient boosts in the form of liquid fertilizers to keep producing plenty of flowers. There are several options, such as nettle water, “golden water” (diluted urine), or soaking a handful of chicken manure in a watering can for a day or more.
For those who don’t prefer these methods or live in an apartment without space for such preparations, store-bought liquid flower fertilizer is also a great alternative.
Can you take cuttings from dahlias?
Answer: Yes! It is absolutely possible to take dahlia cuttings, but just like with many other flowers, there is never a guarantee that it will work. Once you have taken the cutting, make sure to plant it in a small pot with soil. Then, place a freezer bag over the cutting and the rim of the pot to create optimal conditions for recovery and root formation. The bag can be removed after 2-3 days.
If roots start to emerge from the bottom of the pot, it’s time to transplant the dahlia into a slightly larger pot or to its final growing location—if the weather allows and the risk of frost has passed.
How do I store my dahlias for the winter?
Dahlias bloom faithfully from mid-summer until the first heavy frost finally takes them. At that point, it’s time to lift the tubers from the soil and prepare them for dormancy and winter storage. The easiest way to do this is by using a spade or garden fork to gently pry them up.
Once the tubers are out of the ground, cut the stems down to about 10 cm (4 inches) above the plant base. Often, a stronger tool like a lopper or large pruning shears is needed, as dahlia stems tend to become quite thick over the season. Shake off most of the soil and trim away any long roots. Discard any tubers that have started to rot, as they can cause others to rot as well. Let the tubers dry for a day or two before storing them for winter—this reduces the risk of rot or mold developing during storage.
Tubers can be stored in plastic crates without lids, paper bags, or cardboard boxes. It’s important not to overcrowd them—placing fewer tubers per storage container increases their survival rate.
Don’t forget to label your tubers if you want to keep track of different varieties! A great tip is to attach masking tape to the remaining stem and write the variety name on it.
Store the tubers in a dark, dry, and cool place. The ideal winter storage temperature for dahlias is around 5°C (41°F), though a few degrees warmer is usually fine.
Now, all that’s left to do is enjoy the winter and count down the days until the next eagerly awaited dahlia season.
Good luck! 🌿✨
Author: Johanna Damm
Fact-checked by Erik Hoekstra
Last updated: 2025-03-03