dahlia 'Knockout'

Grow in full sun, in fertile, humus-rich, well-drained soil enriched with organic matter and general-purpose fertiliser. Pinch out growing tips to encourage bushy plants, and stake. Water freely in dry periods. Lift and store tubers in autumn to replant, or use as a source of cuttings, in spring. See dahlia cultivation

Deadhead to prolong flowering. Cut back to near ground level in autumn, once frost has damaged foliage, before lifting and storing for the winter

Propagate by softwood cuttings taken in spring from shoots from stored tubers, or divide the tubers, ensuring each section has at least one viable bud

May be susceptible to aphids, capsid bugs, caterpillars, earwigs nibbling flowers, glasshouse red spider mite and slugs

May be susceptible to powdery mildews in dry conditions, fungal rots including grey mould in wet conditions and in storage, and a virus that causes stunting, leaf markings and distortion