Planting, overwintering, varieties & cut flower
The dahlia is the queen of late summer. There’s no garden in Lower Austria without it — and no autumn bouquet that feels complete without it.
Anyone who has had dahlias in the garden once gets hooked. No other flower offers such a wide variety of shapes and colors — from the small pompon dahlia to the dinner-plate-sized Dinnerplate dahlia, from white to salmon to almost black. In Austria and the Netherlands, dahlias have been an integral part of garden culture for generations.
Here’s what matters most: when to plant dahlias, how to overwinter dahlias, and why they are so underrated as cut flowers.
Quick profile: Dahlia
Botanical: Dahlia (family Asteraceae)
Origin: Mexico, Central America
Varieties: over 42,000 registered varieties worldwide
Cultivation: Netherlands, Austria, Germany
Flowering time: July – first frost
Vase life: 5–7 days
Hardy: No — tubers must be dug up
Difficulty: medium
Where do dahlias come from?
The dahlia comes from the high plains of Mexico, where the Aztecs used it as a food plant — the tubers are edible. It arrived in Europe in the 18th century, initially as a botanical curiosity. The Dutch and Germans then began systematic breeding, and today there are more than 42,000 registered varieties in 14 official flower forms.
In Austria, dahlias have been popular since the 19th century. They can still be found today in many cottage gardens across Lower Austria, Styria, and Upper Austria — often varieties that have been passed down for decades.
Planting dahlias
The right time for planting dahlias in Austria is after the last frost, around mid-May. The tubers cannot tolerate frost — even a single frosty night can destroy them.
Plant the tuber about 5 cm deep in the soil, with the “eye” (the bud at the tuber neck) facing upward. Leave 50–80 cm between plants, depending on the variety. Tall varieties need a support stake from the start, otherwise they may snap in summer thunderstorms.
Tip: If you want earlier blooms, you can start the tubers indoors in pots from April. Once the last frost has passed, they can go outside — giving you a head start of four to six weeks.
Dahlia varieties
The variety is overwhelming. Here are the main flower forms most commonly found in Austria and the Netherlands:
| Flower shape | Size | Special feature |
|---|---|---|
| Decorative dahlia | Medium to large | Broad, flat petals — the classic |
| Cactus dahlia | Medium to large | Pointed, rolled petals — very elegant |
| Pompon dahlia | Small (5 cm) | Perfectly round flower balls |
| Ball dahlia | Medium | Like a pompon, but larger |
| Dinnerplate dahlia | Huge (20–30 cm) | Dinner-plate-sized blooms — spectacular in the garden |
Overwintering dahlias
Overwintering dahlias is the part that puts many people off — but it really isn’t complicated. Dahlias are not winter-hardy, so the tubers must be lifted from the ground before the first frost.
As soon as the first frost turns the foliage black (in Vienna usually late October to early November), cut the stems back to about 10 cm and carefully dig up the tubers. Shake off the soil, let them dry for a few days, then store them in a box with dry sand, sawdust, or newspaper. Temperature: 5–8°C, dark, dry — an unheated cellar is ideal.
In spring, check the tubers: cut away any rotten or dried-out parts, and replant the healthy tubers from May onward.
Dahlias in a vase
Dahlias in a vase last 5–7 days. Cut them in the morning, once the flowers are fully open (dahlias do not continue opening in the vase). Trim the stems at an angle, remove the lower leaves, and use clean water with flower food. Change the water every two days.
Pro tip: Briefly dip the cut ends of the stems in boiling water (2–3 seconds) before placing them in the vase. This seals the cut surface and noticeably extends vase life. Sounds brutal, but it works.
Dahlia meaning
The meaning of dahlias is gratitude, inner strength, and elegance. In the language of flowers, dahlias say: “I admire your strength.” They are also a symbol of change and new beginnings — fitting, since they bloom in autumn, when everything is changing.
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Frequently asked questions about dahlias
After the last spring frost, so from mid-May onward. The tubers cannot tolerate frost. If you want to get an earlier start, you can pre-sprout them indoors from April.
No. The tubers need to be dug up before the first frost and stored in a frost-free place (5–8°C). Replant them in spring.
Dahlias are considered non-toxic. The petals are even edible and are used as decoration in fine dining. Safe for households with children and pets.
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