I have been inspired by the amazing show of Dahlias at the Christchurch Botanic Gardens to grow them for the first time. When is the perfect time to plant tubers and what soil preparation do you recommend?

Dahlias are herbaceous (non-woody stems), perennial plants that grow from tubers. Perennial means the plant lives up to three years or more. They bloom from around December (depending on the region eg: later in colder climates), through till autumn and there is a wide selection of gorgeous colours and bloom shapes to choose from. 

Spring till early summer is the recommended time for planting new dahlia tubers. Choose a well-drained site, in full sun, and sheltered from strong winds as some Dahlias can grow up to 1.5 meters. 

Dahlias thrive in fertile soil so prepare your site a month or so before planting by adding plenty of compost to the existing soil, especially if it is heavy clay. Check the packet or with your supplier as the depth and spacing you plant tubers depends on the variety you are growing e.g., bedding, medium or tall growing. Always plant tubers with their shoots facing upwards. You can also grow dahlias in pots – use Daltons Premium Bulb Mix.

With tall-growing varieties, place stakes in the ground before planting the new tubers. As the plant grows, tie them to the stakes regularly to avoid wind damage. 

Once the dahlias have sprouted their first set of leaves, give your plants a deep watering 3-4 times per week. To encourage side shoots, pinch out the central growing tip two or three weeks after planting or when the plant has four sets of two leaves. When plants are around 15 cm high, mulch them with Daltons Premium Much and Grow to reduce weeds and conserve water. Apply a light side dressing of Daltons Garden Time Complete Garden Fertiliser as the plants are growing in summer.

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