Cestrum: Greenhouse Plants
FF – frost free only / C – cool, minimum of 7°C (45°F) / W – warm, minimum of 13°C (55°F)
The plant for the frost free house is Cestrum ‘Newellii’ which is thought to be a hybrid of unknown parentage. The tubular flowers are bright red and produced during summer and autumn. The only drawback is that it grows fast and needs some space to do well; probably best trained against a wall or trellis. However, it is redeemed by responding well to being pruned very hard back to retain its shape and vigour. This is best done by reducing the growth after flowering, allowing the plant to become semi dormant during winter and pruning hard in early March or just before growth resumes. I find that C. aurantiacum from Guatemala does better in the cool house although it will live in frost free conditions. It has lovely golden-yellow flowers from June to September but rather disarmingly sheds leaves, until one realises that it is supposed to be ‘sub-evergreen’. C. purpureum (C. elegans) from Mexico prefers it a little warmer and produces an attractive display from May to autumn of reddish-purple flowers with berries the same colour, all on the plant at the same time. These two species also grow tall if left. My favourite method of dealing with this is to train main shoots into the desired shape or size and thereafter prune back the side shoots to within a bud of these older growths. Propagation is straightforward from. Seed may also be sown. Be ever watchful for whitefly.