How to grow beautiful dalhias A complete guide to growing magnificent dahlias and achieving exceptional flowering

Dahlias enchant our gardens with their spectacular flowers in a variety of shapes and colours. From spring to autumn, these plants from Mexico transform our outdoor spaces into veritable tableaux vivants. There are a few essential steps you need to take to ensure they bloom beautifully. Discover our advice on how to grow your dahlias successfully and enjoy their splendid flowers.

When and how to plant your dahlia bulbs?

The success of your dahlias starts with careful planting. Wait until mid-May in colder regions, while milder areas allow planting from the end of March. Prepare holes 15 cm deep, spaced 50 to 80 cm apart depending on the variety.

To encourage an optimum start, enrich your soil with compost before planting. Place the bulb point upwards and immediately install a stake for larger varieties. A sprinkling of wood ash around the base will protect your young shoots from slugs.

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The secrets of ideal soil for your dahlias

The success of your dahlias relies on a soil with a balanced composition. A mixture of 50% garden soil, 30% sand and 20% organic matter guarantees optimum root development.

For perfect drainage in clay soils, incorporate river sand. This aerated structure prevents water stagnation, dreaded for tubers. Special geranium potting soil can also be used, as its rich, draining composition meets the nutrient requirements of dahlias.

Watering and fertilising dahlias

Regular, controlled watering is the basis for exceptional flowering. Water deeply, at a rate of at least five litres per tuber, avoiding wetting the foliage to prevent disease.

In summer, water early in the morning or in the evening to limit evaporation. In hot weather, a natural mulch helps to keep the soil moist.

Fertilisation plays a key role in the vigour of the stems and the abundance of buds. Choose a fertiliser rich in potassium and phosphorus, applied every fortnight as soon as the first flowers appear. Organic gardeners will opt for diluted nettle purin, an excellent natural stimulant.

In a nutshell about growing dalhias

Choose rich, well-drained soil

Prepare loose soil, enriched with compost, for good growth.

Water generously but not excessively

Prefer two deep waterings a week

Prune and divide for more flowers

Pinch and cut off spent flowers and divide clumps

How to maximise the flowering of your dahlias

Regular pruning of faded flowers represents the most effective gesture for stimulating abundant flowering. Cut the stems just above a lateral bud, at 45 degrees, to encourage the birth of new shoots.

The right staking ensures strong stems capable of supporting the weight of the flowers. Install bamboo supports as soon as the plants reach 30 cm in height.

Pinching young shoots at the 3-4 leaf stage doubles flower production. This simple technique creates bushier, branchier plants.

Protect your dahlias from heavy rain with transparent cloches. This protection keeps the flowers intact and prolongs their bloom until the first frost.

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Protecting and conserving bulbs in winter

As soon as the first frosts arrive, your dahlias deserve special attention. Tubers are particularly afraid of frost and excessive humidity. In mild climate regions, a thick mulch of dead leaves or straw is enough to keep them in the ground.

For colder areas, uprooting is essential after the first frost. Gently clean the tubers and leave them to dry for 48 hours in an airy place. Optimum storage requires a crate filled with dry sand or peat, kept in a dark room at between 5 and 10°C.

Check monthly to spot and quickly eliminate any signs of mould. By spring, your tubers will be ready for another spectacular flowering season.