Quick Guide: summer/autumn, half-hardy, sun/semi-shade, height: 45cm/18in, width: 45-60cm/18-24in

Long-lasting and excellent for cutting, dahlias are among the most popular summer flowers. The types grown from tubers are called border dahlias, which are divided into groups, namely: Single-flowered; Anemone-flowered; Collerctte (with a collar of smaller florets); Peony-flowered; Decorative (large ray florets, reminiscent of chrysanthemums); Ball; Pompon; Cactus and Semi-cactus (pointed petals). Decorative, Ball and Cactus dahlias arc further subdivided by size. The colour range is wide, excluding blue, but all shades have a characteristic clarity and brightness. Dahlias are in glorious bloom from high summer until the first frosts. The minimum height is given above - some varieties reach 1.5m/,5ft.

GROWING Dahlias are best grown in a special bed on welldrained soil previously enriched with well-rotted organic matter. Just before planting, rake in bonemeal at 100g/m'- (4oz/ sq.yd). Place a stake in each planting hole to support the stem to within 30cm/12in of its ultimate height. Plant unsprouted tubers in spring, 12.5cm/5in deep. Plant sprouted tubers in late spring or wait until summer in cold wet seasons. As the plants grow, tie the stems loosely to the stakes. For additional growing advice, see nest entry.

When dahlias are grown for exhibition purposes, a process of disbudding is carried out to produce fewer, larger flowers. This is not necessary in normal circumstances, but it is advisable to pinch out the leading shoots once, a month after planting. Lift and store the tubers annually. Raise them carefully, using a spade, a week after frost has turned the leaves black. Drain off water from the stems. Store healthy tubers only. Place them in boxes, just covered with peat, in a frostproof place. Inspect from time to time to make sure none is affected by mould.

PROPAGATION Set overwintered tubers in boxes of peat and sand in spring, with the crowns visible. Keep moist and frostfree. When the 'eyes' begin to swell, cut the tubers into pieces, each with an eve,' and pot up or plant 10cm/4in deep in a cold frame. Plant out when danger of frost is passed.

VARIETIES Single: `Sion', bronze; Anemone: `Lucy', purple, yellow centre; Collerette: 'Can-Can', pink, yellow inner ring; Decorative: `Little Tiger', red and cream, dwarf; Ball: `Gloire de Lvon', white; Pompon: `Nero', maroon; Cactus: `Bach', yellow.

POSSIBLE PROBLEMS Aphids, caterpillars, earwigs; grey mould, petal blight