Chinese Trees Flower in Cambridge

Carrierea calycina and Firmiana simplex have flowered in Cambridge University Botanic Garden for the first time

Two rare and unusual trees have flowered in Cambridge University Botanic Garden for the first time. In early June 2007, a few creamy-white flowers were spotted on a specimen of Carrierea calycina, one of the hardy members of the family Flacourtiaceae. Planted in 1986 on the main lawn, it has now formed a small tree about 4 m high with spreading branches. The heart-shaped sepals form a cup-like flower about 3 cm long, containing numerous stamens and contrasting nicely with the reddish petioles of the leaves. A native of western China, it was introduced in 1908 by Ernest Wilson, but remains very rare in cultivation. The first flowering in the UK was recorded in 1929.

The second tree is Firmiana simplex in the Sterculiaceae and also from China, where it is widely cultivated as a street tree; it is also popular in Japan and Taiwan. It was introduced in 1757, but has always been considered suitable only for the mildest localities or as a glasshouse specimen. Our specimen, planted in 1990, is growing in the shelter of our glasshouse bays, where its large 3–5-lobed leaves add a touch of exotic foliage. It is now nearly 6 m tall and it was a surprise to find it covered with numerous inflorescences in mid June; we expect the small yellow flowers to open in mid July. Could this be the first flowering outdoors in the UK?

I am inclined to speculate that these two unusual flowerings could be down to the very high summer temperatures we have experienced in previous years. This is perhaps supported by the spectacular and profuse flowering of Aesculus californica and Cladrastis kentukea this year, both from the south-west USA. If this is the case, we might expect other gardens to have unusual flowerings and we would be interested to hear from them.

Tim Upson, Superintendent, Cambridge University Botanic Garden