Lift dahlia tubers as soon as the first frosts have blackened their stems and store them for winter.
Dig up the fat hand-like roots carefully, making sure you don't accidentally spear them with your fork. Then brush off any excess soil and trim back the foliage to leave about 10cm of stem above the top-most tubers.
Tie a label round the stem so you don't forget which variety it is, then move them indoors and stand upside down in a tray lined with newspaper so any excess moisture can drain out of the stem. Alternatively, the slats in greenhouse shelving make great drying racks.
After a day or two, turn the tubers upright again and sit them in wooden crates (avoid plastic as they may 'sweat' and rot). Cover with just-damp soil or old compost, so that just the crowns are visible, and store in a cool, frost-free place. Then in spring you can pot them up again in roomy containers to start them into growth: when you see strong, sturdy shoots emerging it's time to harden them off and move them back outside again once you're sure all danger of frost has passed, for another breathtaking display of dazzling colour next year.
