Dahlias are easy to grow but do need winter protection in most parts of the UK. They are tolerant of a wide range of soil types and situations but best planted in fertile, well-drained soil in full sun when danger of frost is over, usually May to early June. Planting could be carried out slightly earlier in southern counties or later in the north of England and Scotland.
- Incorporate plenty of organic matter (one or two buckets per sq m/sq yd) such as well-rotted manure into the soil prior to planting and use a general purpose fertilizer, according to the manufacturer’s instructions
- Plant tubers in their flowering position. Tubers should be planted 10-15cm (4-6in) deep
- Stake as required and pinch out shoots to promote bushiness (see pruning and training below)
- Keep well watered and once flowers appear feed with a high potash liquid feed every two weeks from July to early September
Cut plants to the ground after the first frosts have blackened the foliage. In mild regions and on well-drained soils, leave the tubers in the ground and cover with a 7.5-15cm (3-6in) deep layer of bark chips or garden compost to protect them from frost. In colder areas or on heavy soils, lift and store the tubers (see below) and replant the following spring.
Lifting and storage
- Cut down foliage and use a fork to carefully prise plants out of the soil
- Dry off naturally and then clean away any soil clinging to the tubers. Trim stems to 15-20cm (6-8in). If the tubers have been washed, position them upside down in a cool place for a few weeks to dry off
- Trim off any fine roots
- Place tubers in shallow wooden boxes or open trays and pack with a peat-free compost or dry sand, just covering the tubers but leaving the crown exposed
- Store in a dry, cool, frost-free place. If stored in a garden shed cover with newspaper if a hard frost is predicted
- Inspect tubers regularly during winter for rotting and discard any that are unhealthy