• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Never a dull dahlia

Debranching, disbudding and deadheading: by following a few basic rules, prize-winning dahlias can be yours

Summer has tailed away and many garden plants are starting to look past their best. This is the time for dahlias to shine. They'll flower with ease from midsummer until the first frosts.

Big, small, D. 'Hadrian's Sunlight'showy or dainty, there's a dahlia for everyone. Dahlias have a wide range of flower shapes: single-flowered types, doubles, pompons and many inbetween. The ginormous ones are known as ‘dinner plates’.

I look after the Dahlia trial at RHS Garden Wisley, and feel very privileged to do so. There are 80 cultivars in this trial. 20 are dwarf varieties growing in containers. It's difficult to choose a favourite. The single-flowered D. 'Hadrian's Sunlight' has a wonderful contrast between foliage and flower colour. With its warm yellow flowers and dark purple leaves, it can break up a mass of green in a leafy border.

The entries that are grown in the ground are supported by wire frames. As the plant grows, the frame is moved up to a suitable position to stop the plant rocking in the wind. Too much flexing can cause stems to snap or fall, especially if there is a big, heavy flower on top.

It's important tDahlia stakingo dead head your dahlias. This will stimulate further buds and bigger flowers to create a longer and better display. Every year, dahlia enthusiasts try to grow and exhibit their best and biggest flowers. This is done by 'debranching' - removing entire stems at an early stage of growth, and 'disbudding' - removing side buds. These procedures concentrate more of the growing energy into one magnificent flower.

disbudding dahliasDahlias are not fully hardy. You can either lift them in late autumn and store the tubers in a place where they will be free from frost, or you may decide to take your chances and leave them in situ. If you do this, mulch well over the top of the plants.

Dahlias are wonderfully rewarding plants and, in my opinion, a must-have for every gardener. Please come by the trials field this month to see the wonderful range we have on display.

Useful links

Dahlia cultivation

Trials at RHS Garden Wisley

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