Growing Dahlias

Dahlias give a full-on display of flowers from July until the first frost of the autumn.  They are perfect for providing masses of colourful cut flowers.  They are available in a huge range of colours and flower forms to suit all tastes.  Some have dark, almost burgundy foliage which can add extra interest to a border.  The smaller varieties grow well in pots.


Dahlias grow from tubers; you can either buy them as the dry tubers or as leafy plants in pots.  They are frost sensitive.  In Patrick’s Patch we are able to plant the tubers in early May.  The shoots emerge about two weeks later.

Choose a sunny site, enrich the soil with organic matter and general fertiliser (such as blood, fish and bone).  Plant the tubers where they are to flower about 15cm deep and mark with a cane.  You can also start the tubers growing in pots in the greenhouse in March.

Patrick’s Patch Tip – we notice that the emerging dahlia shoots are very attractive to slugs.  At first signs of the shoot put out some method of slug control such as ferrous sulphate based slug pellets.

Some varieties will need staking with string and canes.   This is best done before the plants get too big.

Through the growing season dead-head and pinch back the tips to promote bushiness.


Once the first frost has blackened the foliage you can lift the dahlia tubers.  Cut the foliage down and lift the tubers.  Allow them to dry off in the sun and then gently rub off most of the soil.  Do not wash as this can promote rotting.  Store in dry, dark shed.  Small tubers are best half covered with dry compost.  Tie labels on the tubers ready for the next year’s planting. Alternatively, you can leave the tubers in the ground.  In Patrick’s Patch we leave some of our dahlias in the flower border.  They are cut down and a mound of bark chippings put over the crown to keep the frost off.

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