Can you smell your Katsura tree?

Bright red autumn colour on a bonsai Katsura tree

One of the most remarkable aspects of this tree, the Katsura is around now for all to smell, it is the wonderful onset of autumn colour and smell which sets the taste buds alight. The leaves as they go into senescence (autumn colour) emit a fabulous scent which is described as that of

candy floss or burnt sugar. It is a sweet fragrance that lingers in the air and you know when there is Katsura around even if you cannot see it.

Leaves of a mature Katsura tree

Mature Katsura tree at Heal Gardens in Wiltshire

The Cercidiphyllum japonicum is the one most commonly used in bonsai and originates from Japan and China. The Katsura is deciduous and can grow into a medium to large tree and there are some very good examples to see for example at Westonbirt Arboreutm, Heal Gardens in Wiltshire and Kew Gardens.

Branch structure of mature Katsura tree

They are a very attractive tree, when mature or kept as a bonsai and have a similar leaf shape to that of the Judas tree (Cercis siliquastrum). However, the heart shaped leaves are smaller on the Katsura and opposite as opposed to alternate in pattern. The autumn colour is stunning, as the leaves turn a vibrant red from a pink hue or they may go from green to yellow too.

Yellow autumn colour of a Katsura at Westonbirt Arboretum

Bonsai Katsura autumn colour

Katsura trees have male and female flowers on separate trees so are dioecious. The Male trees have small tufts which are in fact tiny red flowers on the spur shoots in late winter prior to the leaves. The trees female tree goes on to produce clusters of pea pod winged shaped seeds from the small bunches of dark red twists at the nodes. The genus Cercidiphyllum from the Cercidiphyllaceae family contains only 2 species within it, that of C. Japonicum and C. Magnificum, however there are cultivars of C. Japonicum which include var. Magnificum, ‘Pendulum’, ‘Rotfuchs’ and var. Sinense.

Opposite buds of the Katsura tree

The natural form of the Katsura is usually that of a conical form with graceful narrow branches and opposite bud formation. They tend to have evenly spaced branches and sub laterals that become pendulous at the tips. They prefer a slightly acidic soil which provides the best conditions for good autumn colour. They are fully hardy but prefer sheltered shaded locations and prefer a moist as opposed to dry soil. Optimum pruning time is around autumn to late winter when the tree is dormant and they will withstand pruning well. They can be propagated from seed, layering, air layering and stem cutting.

Heart shaped leaf of a bonsai Katsura tree

Few bonsai books make reference to the Katsura tree as a bonsai, one or two do make mention that is it a suitable species for bonsai but with limited guidance. However it is suggested that it does make a good informal upright, upright, slanting, semi cascade, cascade, broom, twin trunk, clump, multiple trunk and saikei styles. In terms of size small to extra large have been tried and all appear to work well. I have found some good examples on line and one in particular that caught my eye was that of a Katsura from yamadori. http://snsyamadori.co.uk/gallery

They are generally trouble free from pests and diseases, and require fertilising throughout April to September once the leaves appear up until just prior to leaf fall. If you need to wire do this in the summer as required but beware that the younger branches are fairly delicate and they do scar with wire. If you are looking to leaf prune, July is the time and keep the foliage trimmed in spring and summer but do the structural pruning during the dormant period and remove deadwood in spring. Re-potting either annually or every two years in spring before bud burst and they grow prolific roots if kept overly moist and tolerate heavy root pruning when re-potting.

This is a species of tree that is great for the smell, leaf shape and colour, I have not yet created a fully successful bonsai out of the ones I have but I am keen to continue to try as they do look and smell great at this time of year.

References

  • Bricknell, C & Joyce, D (1996) Pruning and training. A fully illustrated plant by plant manual. Royal Horticultural Society
  • Gianfranco Giorgi (1990) Guide to Bonsai. Simon & Schuster Inc
  • Hillier, J & Coombes, A (2002) The Hiller Manual of Trees and Shrubs. David & Charles
  • Levy-Yamamori, R & Taaffe, G (2004) Garden plants of Japan. Timber Press
  • Mitchell, A (1974) Collins Field Guide Trees of Britain and Northern Europe. Harper Collins Publishers
  • Moore,D & White, J (2003) Trees of Britain and Northern Europe. Cassell
  • Page, M (2001) Name that plant. An illustrated guide to plant and botanical Latin names. Worth Press
  • Tomlinson, H (1990) Bonsai pocket encyclopaedia. Dorling Kindersley Limited London.

Other sources of information