How to Grow Dahlias
Despite originating from the warmer climate of Mexico, dahlias are surprisingly easy to grow in the UK. They are very tolerant of a number of soil types and conditions, but like most plants, they will do much better in fertile, well drained soil which gets plenty of sun during the day.
Generally, dahlias will flower from May to June, but this will vary across Britain according to the climate and light conditions. Dahlias can be planted out as soon as there is no longer a risk of frost, so they could probably be started earlier in southern areas and a few weeks later in the north. If overwintering dahlias, make sure that they are well protected.
When planting, make sure that plenty of organic material and an all purpose fertilizer is mixed in to the soil. Plant the tubers into the positions where you would like them to flower. For the best results, make sure that they are planted about 6 inches deep (15 cm).
Dahlias can become very tall, so be prepared to support them as they emerge and grow. Pinch out any shoots to encourage a stronger bloom and always make sure that the dahlias are kept well watered, dosing with a high potash plant feed as soon as the flowers heads appear. Continue to feed every two weeks during July to September. Always remember to read the manufacturer’s instructions when using fertilisers and plant food.
Deadhead the dahlias as soon as the blooms have faded.