How To Look After Dahlias Over Winter
Dig up and dry out dahlias at the end of autumn
Bronze leaved dahlias at Levens Hall, Cumbria (pictured above)
Dahlias are one of the best garden plants as they will flower well into autumn, until the first frosts, just keep picking them and they will keep producing more flowers. They provide a splash of colour in the garden when all other herbaceous plants are starting to fade. They are originally from the mountainous regions of Guatemala and Mexico, where it is the national flower. The plants typically grow to heights of 30 – 90cm (12 – 36”), although the Tree Dahlia (Dahlia imperialis) can reach a height of 6m (20’). The individual flower heads can vary between 5 – 25cm (2 – 10”), they’re not all huge and brash however, there are a lot of small, dainty single varieties. There are now approximately 57,000 named cultivars. The tubers are tender and as such must be either mulched or brought into a frost free environment. If you live in an area with frost free, mild winter weather and have good free draining soil it is possible to leave them in the ground; cut them off to within 5cm (2”) of the crown and cover with good garden compost or chipped bark to a thickness of about 10cm (4”).
- When the first frost has blackened the foliage, gently prise up the tubers with a garden fork. Take care not to damage any tubers as they won’t survive the winter.
- Cut off the tops to within 10cm (4”) of the crown.
- Stand upside-down somewhere cool and dry and allow them to dry off naturally. Do not wash them otherwise any trapped damp will rot the tubers.
- Brush off the soil as it dries and trim off any fine roots.
- Place them in shallow boxes and cover up to the crowns with barely damp peat-free compost or sand and store them in a cool, dry, frost free spot. Make sure the mice cannot reach them.
- Keep checking regularly over the winter and if you find any mouldy or soft tubers discard them.
- If you grow them in pots take them out and dry them as above. There is no point in leaving them to dry out in the pot as they will need re-potting into fresh compost in the spring.
In spring the tubers will start to shoot and you can take cuttings or else just plant the tubers when the soil conditions are favourable.