Dahlia – planting and care

Scientific name (Latin): Dahlia

Family: Asteraceae

The dahlia originally comes from the mountains of Mexico and Guatemala. The Aztecs discovered it as early as the 16th century and cultivated it then for its edible roots. A couple of hundred years later, the flower made its way to Europe by sea, and now there are about 50,000 beautiful varieties. The tubers are certainly good, but today few people prefer to eat them rather than experience the magnificent flowering.

You can grow Dahlias both from seeds and tubers, with tubers being the fastest and easiest option. For the blooms to last a long time, it's best to pre-cultivate the dahlia tubers indoors in the spring. Most varieties can be started as early as the period from March to May (earlier in the warmest parts of the country, and later in the coldest). The tuber must have so-called eyes to grow; these look like small knots or buds.

If you want to grow Dahlias from seed, you should start with pre-cultivation indoors in the spring, in April or May.

1. Take out your newly purchased or overwintered tubers. Cut off any rotten or damaged parts, as well as thin and tangled roots.
2. Let the tuber soak in water for 15–30 minutes if it feels dry and shriveled.
3. Plant your tubers in smaller pots or plastic bags. There should be a few centimeters of soil around the tuber, and the shoot on the tuber should stick up. In the beginning, the tuber only needs a very small splash of water. If the tuber gets too much water in the beginning, it can easily rot, so be careful. It is also possible to wait a little with watering, but after a couple of weeks, when it starts to grow green, it must get its first sip.
4. Place the pot or the open plastic bag in a bright and cool place, but above 15 degrees Celsius.
5. If you want, you can take cuttings from the plant when it has reached about 20 cm in height. Then cut off half of it and place the cutting in moist soil. In addition to getting an extra plant, you get a bushier and branched mother plant – but be aware that this can also delay flowering somewhat.
6. If you have plenty of space inside, you can repot to slightly larger pots when the plants have reached about 30 cm in height, but it is also fine to let them stand in the same pot until they are to be planted out.

Always harden off the plants before planting them out – that is, slowly acclimate them to outdoor life by moving them outside during the day and in at night for a week or two. Dahlias are sensitive to cold and cannot tolerate frost, so wait until the risk of night frost is over. Plant in sun and in a sheltered spot away from the wind, and prepare a support for tall and heavy flowers.

Should the fine weather change and the weather forecast warn of temperatures that creep down towards 0, you can to some extent protect the planted dahlias with a fleece fabric through the night.

Dahlias need a lot of soil; it should be both deep and airy. The plants also benefit from being watered with nutrients about every three weeks, preferably with fertilizer that has a low nitrogen content.

Established dahlias are thirsty and will need plenty of water. However, while they are young, you should water more carefully so that the tuber does not rot.

If you're going to have Dahlias in a pot, it's important to choose a large pot. Dahlias need a lot of soil to thrive; the lower varieties need around 20 liters, while the tall ones need 30 liters. With drainage holes in the bottom of the pot, excess water can drain out.

If you're only going to plant one Dahlia in the pot, we recommend going for one of the more eye-catching varieties, for example, the plate-sized 'Otto's Thrill', which hovers a meter above the ground like a pale pink dream.

• In the autumn, just before the frost arrives, you cut off the flower stalk and take the dahlia tubers out of the ground.
• Rinse off the soil and let the tubers dry for about 24 hours.
• Remove rotten and damaged parts, as well as long root threads.
• Store the tubers cool, but frost-free, throughout the winter. You can wrap the tubers in newspaper, bury them in dry sand, or place them in a box with sawdust.
• Take a look at them now and then, and check that they are not about to mold or dry out. If they look very dry, you can spray them with a little water, but usually, they manage fine on their own until next spring.

TIP! If the tubers have several "eyes" (knots/buds), you can divide them in the spring and get more fantastic flowers.

There are several varieties of the dahlia flower, each one more beautiful than the other. Many choose to have a bed with several varieties in different colors and shapes to highlight the floral splendor. The flowers are usually divided into groups. Here are some examples:

• Decorative dahlias:
• • Produce large flowers and offer a rich bloom throughout the summer.
• Pompom dahlias:
• • Round, ball-shaped flowers in many different colors.
• Ball dahlias:
• • This dahlia is also round in shape, but slightly larger than the pompom dahlias.
• Cactus dahlias:
• • A wildly growing plant that resembles a sea plant more than a cactus, with petals that can resemble corals.
• Water lily dahlias:
• • The largest dahlia resembles water lilies in shape, with a more open flower than the rounder varieties.

Which dahlia fascinates you more than the others? Express yourself in the garden among the many different varieties, or choose one or more that give your garden the color splendor you want.

With the right conditions, dahlias are actually a fairly easy-care plant that provides abundant blooms throughout the summer. The more flowers you pick, the more the plant will produce. This is a delightful characteristic of dahlias, so take the opportunity to create many lovely bouquets and enjoy the summer season.

You are here:

• Tips and tricks - Plant guides