Dahlias: expert tips on cultivation & care
Dahlias are lush and beautiful flowering summer plants. But for a successful flowering, there are a few things to keep in mind when dealing with dahlias.
Dahlias – usually bought as tubers and found in many gardens – have long been one of the most popular ornamental plants. Originally native to Mexico, the exotic dahlia (Dahlia) found its way to Europe via sailors in the 18th century and has been a hit in gardens and parks ever since. The perennial, which belongs to the composite family (Asteraceae), can also be easily grown in your garden with a few tips and tricks. We put together all the important info for you.
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Dahlias: importance and flowering time
The genus of dahlias includes about 35 species, some of which are very different from each other visually. Curiously, the name dahlia does not come from the discoverer of the plant in the New World, but was dedicated to the Swedish botanist Andreas Dahl when it was first cultivated in Europe. Dahlias fill our gardens with their brilliant blooms every year starting in July and can continue to bloom into the autumn.
Buying dahlias: as a tuber or grown plant
The most proven method of growing dahlias is through tubers, which are placed directly into the soil. But first, the question arises: how and where to buy dahlia tubers and what to look for?
Buying dahlia tubers
Dahlia tubers can be easily purchased at any garden centre, often they are sold directly to several. There are a variety of different shapes and colours to choose from. In any case, be sure to take only healthy tubers without any rotten areas.
Buying dahlias in a pot: What to look for
Much more difficult than buying in bulb form is to buy dahlias as a whole plant. If you decide to buy a plant directly, the time of flowering can be advanced by several weeks. By the way, the same applies to dahlias grown in pots.
The most beautiful and abundantly flowering varieties
Few ornamental plants have such a great variety as the dahlia. In total, there are 13 different flower shapes, each with a different colour. We present the most attractive and popular varieties:
- Ball dahlia: Around and relatively small flowers; very dense petals; among the most popular dahlia varieties.
Popular varieties: Peter, Marble Ball - Pompom dahlia: Around and flat flower with fully rolled petals; very decorative.
Popular varieties: Barbara, Rocco - Cactus Dahlia: Around flower head with pointed petals; colourful marbling.
Popular varieties: Cheerio, Spassmacher - Water lily dahlia: Flat flower with petals leading outward; water lily appearance.
Popular varieties: Paso Doble, Creme de Cassis. - Deer Antler Dahlia: Fringed and protruding petals; somewhat “wild” look.
Popular varieties: Galaxie, Alauna Clair-Obscur
More interesting dahlia varieties can be found here.
Planting dahlias: instructions and procedure
Spring to early summer is the time and dahlias can be planted in the garden either as a plant or a bulb. This step requires some info, to ensure the dahlias have a good start in the bed and the striking flowers in all their shapes and colours really sprout.
The perfect location
As a subtropical plant, the dahlia certainly has higher requirements than one would initially assume. When planting, make sure the dahlia is in a full-sun spot where the soil is nutrient-rich and well-drained. To do this, always work compost into the soil before planting. Good water drainage is essential, as dahlias are sensitive to waterlogging.
When is the right time to plant dahlias?
An important point for success when planting dahlias is the right time to plant the bulbs or perennials. Dahlias do not tolerate frost and should therefore be planted out in May at the earliest, as soon as the last late frosts have passed. Starting too early can cause your plants to die due to the risk of cold.
Planting dahlias: Instructions on how to do it
- Select a suitable location. The site should be sunny and the soil well-drained and rich in nutrients.
- First loosen the soil and work in plenty of compost, so that the plant has enough nutrients as it grows. If the soil is very rich in clay or loam, it is worth mixing in a little sand.
- Dig a hole in which to place the tuber. The planting hole should be deep enough so that the tuber is completely covered with soil, and the upper part is a few centimetres below the surface of the soil.
- Leave the dahlia bulb in water for a night before planting so that it can reabsorb enough moisture after storage.
- Then place the tubers in the planting hole with a planting distance of 30 to 100 cm – the size of the plant differs depending on the variety. When inserting, it is important that the thicker part of the tuber faces down and the root neck faces up.
Propagating, dividing and forcing dahlias
If you are reluctant to go back to the shop to increase your dahlia stock, there are several alternatives for propagating the magnificent flowering plants. We present all the options.
Propagating dahlias by cuttings
A very quick method of propagating dahlias is to grow cuttings. This technique works by forcing the dahlia tubers in late winter at elevated temperatures. Lightly embedded in soil, the bulbs sprout so that you can break off cuttings with a few pairs of leaves after a short time. After that, the dahlia cuttings are put in growing medium and sprout anew.
Successfully dividing dahlias
A proven method of propagation of dahlias is the division of tubers. Cut the bulb in the spring before planting with a sharp and clean knife so that each part still has at least two buds. As a rule, larger tubers are divided into two smaller ones. The new shoots subsequently develop from the buds when planted.
Forcing dahlias
Similar to the cultivation of cuttings, the early cultivation of dahlias indoors is done from March, with the difference that the plants are left on their tuber.
The perfect dahlia care
Dahlias do not require a great deal of care, but certain aspects should not be ignored, even with this exotic plant. We show what needs to be considered.
Fertilising and watering dahlias correctly
Basically, the level of fertilisation required for dahlias is manageable. Before planting, it is always a good idea to work compost into the soil. Fertiliser containing nitrogen leads to increased leaf growth in dahlias, but also lowers the plant’s willingness to bloom. Therefore, a flower fertiliser that is not too nitrogenous is a good choice. Our Plantura Flower Food meets these requirements and also promotes a healthy and active soil life. This can be worked in regularly and superficially until August.
- Perfect for flowering plants in the garden & on the balcony
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Watering should also be moderate, as dahlias do not tolerate waterlogging well. Water the plant as needed every few days when the soil has dried out. On the other hand, during more intense periods of heat in the summer, you should water more, because the sprawling plant evaporates a lot of water at high temperatures.
Pruning dahlias
For dahlias, pruning in appropriate places can provide a greater abundance of flowers and affect the shape of the plant. It is therefore advisable to cut the shoot tips sporadically, especially in the young stage, in order to increase branching and thus flower formation. Withered flowers should also be cut off so that new shoots are formed.
As a general rule: If you leave a few shoots on the plant, the larger the respective flowers will be.
Caring for dahlias in a pot
Dahlias in pots are very easy to care for and require comparatively little attention. Since the soil naturally dries out faster in pots than outdoors, you should still always keep an eye on the moisture of the substrate and avoid complete drying out. Just as in the open ground, withered flowers should be removed regularly.
Controlling common diseases and pests
The most common diseases and pests of dahlias are presented below:
- Snails: Particularly troublesome, as they can eat much of the greenery in a very short time. Remedies are snail traps and fences as well as collecting the animals in the early morning.
- Aphids: Small black or white insects that feed on the plant. Dabbing the affected areas with dish soap helps. Ladybirds act as a biological control.
- Grey mould: The Botrytis fungus can be recognised by the grey coating. Do not plant too densely and avoid high humidity, do not wet the plant with water and avoid nitrogen fertilisation.
- Mildew: Can be recognised by the whitish coating. The risk can be reduced by the same measures as for grey mould.
- Mosaic virus: Recognisable by yellowish spots on the leaves. The best countermeasure is to remove the plant to prevent further infection.
You can find more about caring for your dahlias here.
Overwintering dahlias: are dahlias hardy?
Due to their warm origins from Mexico, dahlias are not frost resistant and therefore not hardy. Leaving the tubers in the ground is at your own risk and can only succeed in very mild regions if adequate winter protection of brushwood, straw and leaves is spread over them. However, as a rule, the tubers should be dug up immediately after the first frost. To do this, first cut the plant to 10 cm above the ground and gently dig up the bulb. In a dry and cool, but frost-free place, the individual tubers can now be stored until spring. Before storing, remove the soil and spread the tubers out to air with a little space between them.
Further tips on the ideal overwintering of dahlias can be found here.
