HOW TO GROW DAHLIAS

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Who can resist growing Dahlias in your garden when there are so many varieties and colours to choose from. They are a firm favourite of mine, and add impact to any garden. They make excellent cut flowers and some blooms are as big as your head. 

Dahlias come in a variety of forms, having been cultivated for hundreds of years. Dahlias originated as species types and single blooms, but then were cultivated to produce hybrids such as double and semi double forms. These were then followed by pompon, collerette and cactus style blooms. Today there are 14 recognised Dahlia groups; singled flowered, anemone flowered, collerette, waterlily, decorative, ball, pompon, cacti, semi-cacti, miscellaneous, fimbricated, star, double orchid and paeony flowered dahlias. 

Favourite varieties of mine include 'Bishop of Llandaff' for its zingy pillar box red semi double flowers on dark black-red foliage and stems. 'Claire de Lune' is a pale yellow collerette form which has two rows of petals; an outside row of large rounded petals and an internal row of shorter petals, and fresh green foliage. 'Moonfire' has bronze foliage and single yellow flowers that are red around the central disc. 'Honka' is a yellow star flowering type with petals rolled inwards along their length. The rich orange double blooms of 'David Howard' contrast with its dark purple foliage.

You can plant out Dahlia tubers directly into the soil after the risk of frosts have passed, usually from April onwards. Alternatively you can pot tubers up from February onwards and keep the emerging plants in a frost free location until they are ready to plant out in the garden in late spring. 

It is recommended to pinch out the growing tops of the plant as it grows to encourage bushy plants. In addition you need to remove all but five shoots from the tuber to ensure strong and vigorous growth. I find that some varieties are more prone to bush out themselves then others. My much loved Dahlia Bishop of Llandaff is never pinched out or staked and is naturally bushy with prolific flowers, although it is planted in a sheltered position. 

Feed regularly during the growing season with a liquid feed fortnightly. Water well especially during dry spells, about once a week should be sufficient. Your Dahlias may require stalking, especially if you are growing stems for cut flowers of the taller blooms. Use a bamboo cane to secure the stems and tie in every few weeks to prevent your Dahlias from breaking at the base in windy or rainy weather. 

Dead head blooms monthly to prolong flowering. Check regularly for pests and disease. Earwigs like Dahlias especially, so you can either use an insecticide or hang pots filled with straw on canes amongst your dahlias. This will encourage earwigs to seek out the cool pots in the heat of the day so that you can remove them. Slugs can also cause problems especially on new growth so protect with slug pellets or use an organic control such as beer traps. 

Dahlias are tender plants and so will die if hit by frosts. In order to prevent this damage tubers are dug up in the autumn and stored ready to be planted out again in the spring. Wait until the Dahlia foliage has blackened from the frost (usually November) and trim the foliage to 15 cm high. Dig up your tubers and remove any loose soil but do not clean them too vigorously as you require some soil to keep the tubers together. 

It is essential that the tubers are kept dry or they will rot so do not get the tubers wet. However, it is also important not to let the tubers dry out completely. Hang them upside down for three weeks. You can dust the tubers with yellow sulphur to prevent mildew and fungus. Transfer the tubers to a box covered in a shallow layer of moist sand or peat, sitting the tubers on top of the soil. Cover with a layer of compost until just the stems showing and store in a cool frost free place. In late winter you can place the box in a light place and new shoots will emerge a few weeks later. 

I live on the milder south coast of the UK and so experience milder winters than the rest of the UK. I do not dig up my tuber each year but instead apply a thick layer of mulch (often leaf mould) over the bed. I also plant the tubers slightly deeper to add some protection. This method will see the new Dahlia plants emerge in the spring successfully in all but the hardest of winters, and the plants will establish much quicker than pot grown or bed sown tubers. But each year I accept the risk that my Dahlias may not survive if the weather is too cold but that’s the price I pay for low maintenance gardening.

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