Common Name:

General Information

Thuja sutchuenensis is an evergreen shrub or a tree with a pyramidal crown of spreading, ascending branches; it can grow up to 20 metres tall[]. The straight, cylindrical bole can be up to 30cm in diameter[].
The tree produces a valuable wood, but has become too rare in the wild for commercial utilization - though it is still exploited on a local basis. It is sometimes grown as an ornamental.
Thuja sutchuenensis was listed as Extinct in the Wild in 1998, but was rediscovered in October 1999 by a regional team of botanists who found individual trees growing scattered on cliffs and ridges of the deeply cleft mountain. There were no large trees, with most being small or even shrub-like because of their locations at higher altitudes and on exposed ridges. Seedlings are scarce. The more accessible trees have mostly been felled for use in home building and for making various household products. The species may also have gone through a genetic bottleneck and be facing problems of inbreeding depression. Following its rediscovery in 1999 it was re-assessed as Critically Endangered. Further surveys since that assessment have produced more information so that a new assessment is required. Decline over the last three generations is estimated to be 80%. Its known area of occupancy is less than 100 km2 and there is no longer any evidence of continuing decline. The total population is estimated to be between 5,000 and 7,000 mature individuals. On the basis of this information, this species no longer meets the criteria for listing as Critically Endangered. The plant is classified as 'Endangered' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The essential oil in this plant contains thujone. Thujone is a GABA receptor antagonist which allows neurons to fire more easily. In larger doses this can cause muscle spasms and convulsions, and can also be toxic to brain, kidney, and liver cells.
There has been a lot of negative press regarding thujone, particularly in the mid 19th century when thujone was reported to be more dangerous than alcohol - since shown to be exaggerated; and reports in the 1970’s that it might have a similar effect on the brain to THC (found in cannabis) – since found to be incorrect.
Thujone is probably best known for its use in the alcoholic drink ‘Absinthe’. It is also found in the essential oils of many other plants that are used in herbal medicines and foods, including Arborvitae (Thuja species), some Junipers (Juniperus species), Wormwoods (especially Artemisia absinthium) and Sage (Salvia officinalis). There are some legal restrictions in various countries on the quantity of thujone that can be added to foods and drinks and these vary between countries.
Side effects from consuming thujone can include sleeplessness and anxiety but, unless the pure essential oil is used, the quantity of thujone found in plants is well within safety levels. Pregnant women, however, may be advised to restrict their use of thujone-containing plants.

Botanical References

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Range

E. Asia - China (northeastern Sichuan, Chongqing)

Habitat

Mixed angiosperm shrubland and forest, growing on steep slopes and ridges of limestone mountain sides; at elevations from 800 - 2,100 metres[].

Properties

Conservation Status	Endangered
Other Uses Rating
Habit	Evergreen Tree
Height	15.00 m
Pollinators	Wind
Cultivation Status	Ornamental, Wild

Cultivation Details

Thuja sutchuenensis is found in a warm temperate and humid climate with a mean annual precipitation around 1,400mm[]. The climate is humid warm temperate, with a January mean of 2.4°c, a July mean of 24.8°c, and a mean annual precipitation of 1,418mm[].
The tree grows in the wild in mountain yellow-brown earth that has developed from limestone - it is rich in organic matter (2 . 3-3%); with a thick humus layer (around 20cm deep); and a pH in the range 6.2 - 7[].
Plants are tolerant of regular trimming, so long as this does not go back into the old wood[].
The crushed foliage has a pleasant aroma[].

Edible Uses

None known

Medicinal

None known

Agroforestry Uses:

The tree is tolerant of regular light trimming, though should not be cut back into the old wood. It can be grown as a hedge[].

Other Uses

The wood of this species is soft, light, easily worked and durable. It is used for applications requiring decay resistance by local people, e.g. home construction, production of shingles, application for funeral services, etc. It is too rare to possess much commercial value[, ].

Propagation

Seed - best sown when ripe in the autumn in a cold frame[]. Stored seed germinates best if given a short cold stratification[]. It can be sown in a cold frame in late winter. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts.
If growing large quantities of plants, the seed can be sown in an outdoor seed bed in mid spring[]. Grow the plants on for two years and then plant them out into their permanent positions in late autumn or early spring.
Cuttings of half-ripe wood, 5 - 8cm with a heel, mid summer in a shaded frame. Forms roots by the end of September but it should be overwintered in a frame[].
Cuttings of almost ripe wood, 5 - 10cm with a heel, September in a cold frame. Forms roots in the following summer. Plant out in autumn or spring[].