Cercidiphyllaceae

 

This monogeneric Family survives from fairly early in the evolutionary tree of the Angiosperms and is named for the Cercis-shaped leaves.

 

Cercidiphyllum

 

The genus, of highly ornamental trees or shrubs, contains only two species – both of which have an oriental distribution in chiefly temperate areas. C. japonicum occurs in China and Japan and can grow into a substantially sized tree while C. magnificum is a narrow endemic in Japan - it is a much smaller tree but with larger leaves. Both are called the Katsura tree. They are elegant trees or large shrubs and are often multi-stemmed.

 

The plants are dioecious and the flowers are produced in the spring - the female flowers are red and the males are green – and are wind pollinated.

 

The fruits are not often (if ever) seen in the UK because of the need for both sexes to be present and adjacent. Thus imported seed is the norm.

 

The fruit is a follicle and is produced in a cluster of two to four small, dehiscent pods - each between one and two centimetres long. The pods are initially green but mature to a coppery colour. Each pod contains numerous, small, flat, compressed, oily, winged seeds which are released over the autumn and winter. Viability is often low (as little as 20%). The pods should be harvested before they split and then dried to release the seeds. The seeds have thin seed coats and are susceptible to water loss – which can cause a serious loss of viability - so that drying should be limited to causing the pods to open just so that the seeds can be shaken free.

 

The seeds are sown, in a tray, without delay and watered in so that they imbibe and so maintain viability. The whole can then be kept moist through processing and germination. Chilling is not essential for germination but a chill for 14 days at 3˚C will unify and speed germination. Successful chilling can be achieved by enclosing the tray in a polythene bag and then refrigerating before transfer to the germination environment at 20˚C - when emergence will occur in 14 days.