Types of dahlias: flower groups, balcony dahlias and growing

In short: Dahlias are divided by flower shape into groups ranging from single-flowered through decorative, ball and pompon to cactus types. Breeding has produced over 2,000 varieties today. They bloom from summer until the first frosts and do best in a sunny position, in medium-heavy, slightly alkaline soil with moderate watering.

Dahlias are the queens of late summer and autumn. They bloom until the first frosts and come in hundreds of shapes and colours. Say "dahlia" and everyone pictures something different, because the groups differ from one another in both flower shape and size.

In this article you will find an overview of the groups, tips on choosing, and instructions for planting and overwintering the tubers.

What dahlias are

The dahlia (Dahlia) is a genus of plants in the daisy family. It includes about 38 botanical species and originates from tropical America, where it grows from Mexico to Colombia. Through gradual breeding, over 2,000 varieties now exist. Dahlias are propagated by seed, cuttings and division of tubers.

Types of dahlias by flower shape

Among the cactus types, a distinction is made between spiky ones (the tips of the petals curl forward) and fimbriated ones (the petals are frayed at the ends). Orchid-flowered, or "safari", dahlias have bicoloured, cross-striped flowers with petals rolled downwards.

How to choose a dahlia

• For cutting and vases: pompon, ball and decorative types.
• For beds and shrub plantings: decorative, cactus and waterlily types.
• For bees and pollinators: single-flowered types, where the yellow centre is easy to see.
• For balconies and planters: lower-growing varieties.

Dahlias from seeds and from tubers

Dahlias are grown from tubers, which are lifted from the ground every year and stored over winter, or from seeds. Seeds are practical for low-growing varieties. From our range, these are worth a look: garden dahlia double mix and garden dahlia single mix. Plants grown from seed flower in the first year, and the colours may vary.

Low-growing varieties are grown from seed; varieties with an exact colour and shape are propagated by tubers or cuttings. If you want a specific variety, buy tubers from a specialist nursery.

When and how to plant dahlias

1. Choose a sunny spot and improve the soil with compost.
2. For tall varieties, drive in a support stake before planting.
3. Place the tuber in the hole so that the root crown is about 8–10 cm below the surface.
4. Cover it over and water only lightly for the first few days; the tuber must not rot.
5. Once shoots appear, water more regularly, especially in dry spells.

Caring for dahlias

• Watering: moderate but regular. In hot weather, water at ground level.
• Feeding: during the season, compost or a fertiliser with a higher potassium content, see Feed, but don't overfeed!.
• Pinching out: shortening the main shoot above the fifth pair of leaves encourages branching and more flowers.
• Removing spent flowers: the plant then flowers for longer.
• Support: support tall varieties with a stake.

Balcony dahlias

Lower-growing varieties, often grown from seed, are suited to balconies and terraces. Choose a container with a volume of at least 10 litres, with drainage holes and a good substrate. They dry out quickly in a container, so water even daily in hot weather and feed regularly. Place the pots in a sunny spot.

Overwintering the tubers

Dahlias are not frost-hardy. According to sources, the tubers are lifted after the above-ground part has been killed by frost, usually at the end of September:

1. Carefully lift the tubers out of the soil with a spade or fork.
2. Cut the stems back to about 10 cm.
3. Remove excess soil and let the tubers dry off.
4. Store them in a dry cellar at 5–8 °C and an air humidity of 85–90 %.
5. In a dry store, cover them with dry peat, sand or sawdust.

In spring, check the tubers and remove any damaged or rotten ones.

Dahlia diseases and pests

The biggest enemies of dahlias are slugs, which nibble the young shoots in spring. Collecting them in damp weather and barriers around the plants help. Aphids and spider mites suck on the leaves and buds, so check the plants regularly. In muggy weather, powdery mildew appears. Tubers may be attacked by rot in winter, so store them dry and remove rotten parts when checking them.

Dahlias in a vase

Cut dahlias in the morning, when the flowers are fully open. Put the stems into water immediately and cut the bottom end at an angle. Change the water every two days. Dahlias do not ripen further once cut, so do not cut them at the tight-bud stage. With proper handling, the flowers last several days in a vase. Pompon and ball dahlias are the best suited to a vase.

The most common growing mistakes

• Planting before the last frosts: tubers and shoots die in the frost.
• Wet soil: tubers rot.
• Too little sun: plants grow leggy and flower poorly.
• Too much nitrogen: plants grow leaves at the expense of flowers.
• Poor storage of tubers: too much damp or dryness harms them.

Dahlias and zinnias: not to be confused

In everyday speech, zinnias, which have similar flowers, are sometimes also called dahlias. They do not belong to the dahlias; they are a different genus and are grown from seed every year. Examples on offer include zinnia elegans dahlia-flowered and zinnia dahlia-flowered Caroussel. They do not need overwintering, because they die off for the winter.

Frequently asked questions

What types of dahlias are there?

Single, anemone-flowered, collarette, decorative, waterlily, ball, pompon, cactus, semi-cactus and others, depending on flower shape.

When are dahlia tubers planted?

In early May, after the last frosts. Tubers can be pre-grown in a pot in April.

How do you overwinter dahlias?

After the above-ground part is killed by frost, lift the tubers, cut back the stems, let them dry off and store them dry at 5–8 °C.

How many varieties of dahlia are there?

Over 2,000.

Are dahlias suitable for a balcony?

Yes, lower-growing varieties in a container in a sunny spot with regular watering.

Sources

• Dahlia (flower) – Wikipedia
• Dahlia pinnata Cav. – Botany.cz

Updated: 5 October 2026