Sassafras tzumu (Hemsley) Hemsley

Sassafras tzumu was first introduced to the west by E. H. Wilson in 1901 from Hupeh, China (Jacobson 1996; Bean 1981). Wilson noted it was locally known as Tzumu shu, while the more recent Flora of China gives a common name of cha mu. Growing across much of southern China, it makes a large tree to over 35 m tall in open woodlands and forest edges. In cultivation it typically is more of a medium sized tree, growing to 9–15 m in 20 years. When grown in the open it has a distinctly tiered habit much like Cornus controversa with branches emerging laterally in pseudo whorls. Flowers emerge in late winter to early spring where they are often at the mercy of late frosts. In full flower, Chinese Sassafras is as showy as any spring-flowering tree and resembles a large Cornelian Cherry (Cornus mas and C. officinalis) with clusters of terminal racemes bearing bright yellow flowers. The leaves emerge with a touch of burgundy before becoming large and green with the typical sassafras foliage shapes – ovate, mitten-like, and tri-lobed.

Unlike the North American Sassafras albidum which bears unisexual flowers, both Asian species bear bisexual protogynous flowers that are functionally unisexual especially when young (Yang et al. 2022). Fruit set is best when different clones are grown in proximity but single specimens can produce significant crops of attractive waxy blue-black fruits, at least in North America (fruit set in cool-summer regions is very unusual). Autumn colour can be spectacular, with bright gold and orange being the dominant shades. After the leaves drop, stout yellow-green branches with large, ovoid terminal buds provide some measure of winter interest.

The wood is aromatic and used for timber (Diao et al. 2022), furniture building and shipbuilding (Wang et al. 2022) while the bark and roots have been used in traditional Chinese medicine (Traditional Chinese Medicine Encyclopaedia 2024) for the treatment of pain, syphilis, arthritis and other ailments (Willard 2009; Drobnik 2016). Sassafras tzumu wood is also used as a dye for cloth and food (Liu et al. 2014). It is also a popular landscape tree in China (Chen et al. 2020). Although widespread in southern China, S. tzumu is coming under pressure from overharvesting and climate change (Sun et al. 2020).

Where summers do not provide enough heat to harden the wood off, the branches can be quite tender and often will die back in winter but will produce vigorous spring shoots with much larger than typical leaves. Sassafras tzumu is not widely grown but has been distributed by the JC Raulston Arboretum in Raleigh, NC, where there is a fine specimen, to other gardens and nurseries across the U.S. in recent years. The Sonoma Botanic Garden in California has several 2008 accessions collected in Zhejiang Province, China the largest of which is now 6.5 m tall. Pukekura Park in New Plymouth, New Zealand has grown Chinese sassafras for at least 23 years with the largest tree 10 m tall with a dbh of 1.3 m. The U.S. National Arboretum has a plant derived from 1979 seed originally from the Nanjing Botanic Garden; this tree is now over 20 m tall but with a dbh of only 0.34 m.

In the UK, a presumed Wilson original that used to grow at Wakehurst Place, West Sussex, was the largest example known for many years; it was 18 m × 31 cm dbh in 1974 but was lost in 1987. The largest UK examples now grow at Tregrehan, Cornwall, where the better of two good trees was 18 m × 113 cm girth in 2024. Another, at Holker Hall in Cumbria, is notable for being quite far north in an area with cool summers; this was 8 m × 13 cm in 2013 (The Tree Register 2024).

A cultivar, ‘Yellowberry’, is listed in the Botanic Gardens Congress International PlantSearch with no other information on this selection but presumably the fruit does not color to the typical blue-black. There are no records of gardens holding this selection however.