Calycanthus - Growing Guide

Allspice, Spicebush

Three species of Calycanthus are native to California and the SE USA while one, formerly known as Sinocalycanthus chinensis (now C. chinensis), comes from China. Hybridisation between the Chinese and US species has produced some impressive new varieties with larger flowers which have featured on our last two Chelsea flower show stands and sold out on the website before the end of the show.

Calycanthus are fully hardy but they do need to be grown in deep humus-rich soil in full sun or lightly dappled shade for best results. These plants are grown for their unusual fragrant flowers which are perhaps somewhat magnolia-like in shape or perhaps shaped like a tiny water lily. The dark green leaves are 2-8in long and aromatic when crushed.

Allspice grow as freestanding woodland garden plants with us but make excellent floral specimen plants in a shrub border. We seldom prune our plants but, if they do get leggy and over mature, reducing the all over height to 3-4ft may well help initiate better flowering on the younger new growth stems.

Calycanthus chinensis grows to around 10ft with, in maturity, an equivalent spread. A particularly large specimen at Abbotsbury Subtropical Gardens grows on a bank overhanging a seat onto which its nectar falls. The flowers which appear in June are about 3in across and white with smaller inner tepals that are pale yellow with a maroon base.

C. floridus, Carolina allspice, is a dense bushier shrub growing to 6-8ft in maturity. Its flowers are 1½-2in across with numerous strap-shaped dark red petals fading to brown at the tips. The flowers appear in June or July.

The unusual C. floridus ‘Athens’ has very fragrant greenish-yellow flowers in profusion and has only grown slowly with us to 2½-3ft.

C. floridus ‘Purpureus’ has leaves which are tinged purple underneath.

C. occidentalis has leaves and flowers similar to but larger than C. floridus and is known as the California spicebush.

C. x raulstonii ‘Hartlage Wine’ is a cross between C. chinensis and C. floridus. It has striking maroon or wine-red flowers in summer with a circle of creamy white tipped tepals in the centre. This has grown with us to about 8ft with a similar spread.

C. ‘Aphrodite’ is an improved form with exceptionally large red fragrant flowers. It re-blooms right through the summer.

C. ‘Venus’ is also a cross between chinensis, floridus, and occidentalis with 4in wide white flowers and pronounced yellow and purple central markings.

Calycanthus seldom set seed in our climate. The slightly suckering American species can allow the separation of new plants. Softwood cuttings are difficult so this plant may best be propagated by layering.