Clematis 'Walter Pennell'

Clematis 'Walter Pennell' was raised in 1961 by the English breeder Walter Pennell from a cross between 'Vyvyan Pennell' and 'Daniel Deronda' and named in 1974 – a cultivar from the planned breeding programme of the long-established Pennell nursery. The flowers are exceptionally large at 10–20 cm, double to semi-double in early summer, and coloured purple-violet. A carmine-red central bar on each sepal and cream-coloured stamens give them depth and definition.

The first flush opens on last year's shoots in May and June, followed in September by a second flush of smaller, single flowers. At 250 to 400 cm tall, 'Walter Pennell' climbs trellises, obelisks and climbing frames and needs some room to do so. Choose a sunny to semi-shaded, sheltered position with moist but well-drained soil.

'Walter Pennell' is hardy (zone 6, -23.3 to -17.8 °C). Because the double flowers appear on last year's wood, do not prune hard in spring. Instead, cut the plant back to about 150 cm in June – after the first flush; this encourages strong new growth and the September flowers.