Montag, 25. März 2013

Plant of the Day (March 25th, 2013) - Thujopsis dolabrata (Thunb. ex. L. F.) Sieb. & Zucc.

After I have already shown you two of the five ”Holy trees of Kinose”, it's now time for another tree from this group. This tree is Thujopsis dolabrata (Thunb. ex. L. F.) Sieb. & Zucc. from the Cupressaceae family (Cypresses). In English, this plant is known as “false arborvitae” or
“hiba arborvitae”, while in German, it's called “Hiba-Lebensbaum”. In Japan, the tree is known as
asunaro (あすなろ).

Thujopsis dolabrata - habitus (sort "nana")

T. dolabrata is a medium high, evergreen tree, which can reach a maximum height of nearly 15 metres (feet). However, dwarf sorts are also very common. For example, my picture shows the sort “nana”, which reaches a maximum height of only 60 centimetres. 
The colour of the thin bark varies between reddish brown and grey. The small, scale-like leaves are bright green to yellowish green. As with the most members of the Cupressaceae, there are two morphological kinds of leaves: lateral leaves and central (or facial) leaves, which lie flat on the branch.

T. dolabrata - branches and leaves (dorsal site)

The central leaves are inverted egg-shaped (obovate) and appressed, while the lateral leaves are more keeled and lanceolate. They are also a little bit curved and protruding. However, the most distinctive feature of the lateral leaves are the bright and broad ligaments of stomata, which can be found on their ventral side. Both types of leaves are overlapping each other and are between 4 and 7 millimetres long and 2 millimetres broad.

T. dolabrata - branches and leaves (ventral site) -
you can see the bright stomata

T. dolbarata is monoecious, so we have male and female cones on each plant. The male cones are very inconspicuous. They are green and cylindrical. The female cones are spherical and are built of eight fertile seed scales. Female cones are green at first but they lignify with their ripening and get a greyish colour. The pollen fly between March and April.

 T. dolabrata - branches and leaves (dorsal site) - 
closer look: l = lateral leaves; f = facial leaves; s = stomata

At the first glance, T. dolabrata looks very similar to an arborvitae (Genus: Thuja) and the species also belonged to this Genus for a long time. The high similarity to an arborvitae is also the reason for the Latin name “Thujopsis” (what means something like “Thuja like”) and the English name “false arborvitae”. In German, the species is still known as a “Lebensbaum” (German translation of arborvitae).

Thuja occidentalis - brances and leaves; as you can see
the leaves are much smaller and the stomatas aren't so bright
(d = dorsal site; v = ventral site) 

However, there are some differences between the Genera Thujopsis and Thuja. The leaves of T. dolabrata are broader and the female cones are spherical, while the ripe, female cones of a Thuja are more cup-like. So today, T. dolabrata is the only known species of the Genus Thujopsis (a monophylum).

T. dolabrata - habitus

T. dolabrata is endemic to Japan. It grows in cool and moist conifer forests and groves. Its areal reaches from the lower coast to the mountainous regions. As one of the five “Holy trees of Kinose”, this species is also a very popular ornamental plant for temples and shrines. In Europe, small sorts like “nana” and "variegata” can be found in parks, gardens or on cemeteries.

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