Garden Plants - Autumn gardening - Dahlias

Dahlias are at their best in August and September, when the rest of the garden is looking tired and the early summer flowers have 'gone over'. To keep them looking good is a bit of an effort, you either have to lift tubers or take cuttings, and August, September and October are the ideal time for the latter.

For cuttings, plant tubers in a pot or tray of compost, with the old stems just above the surface and grow them indoors in a heated propagator or in a heated greenhouse. Once some green shoots appear, they can removed from the tuber when they are about two inches long and used as cuttings. The tuber from which they came than then be replanted in the garden as normal in spring. Pot up cuttings as soon as they form their own roots and continue to grow them indoors until the danger of frost has passed in late May or early June at which point its time to pot up the plants into larger containers and set them in a sheltered area free from frost. In May, harden them off and then plant them out in the garden between late May and June, depending when your last frost occurs. After planting, pinch out the growing tip of each stem to encourage plants to bush out and form more flowers.

Depending on where you live, each autumn or winter there will be a frost which blackens the foliage of the dahlias, which means its time to life them. Despite the claims that dahlias will survive if left in the ground over winter, you have to treat this as a gamble, not a certainty and if you fancy your chances, you must remember it's a gamble! Dahlia survival will be improved if the tubers are covered with straw or peat. If you thought leaving them in the ground would reduce your workload, forget it. Over-wintered dahlias form large clumps sending up a mass of new shoots in the spring, which need to be lifted and divided if you are to see a decent number of flowers.

Autumn dahlia photograph by KaCey97007, used under a creative commons attribution licence