A new discovery in the Harris Garden
Wednesday, 04 August 2010
Picrasma quassioides discovered in the Harris Garden: image Trevor Pitman
A tree, popularly known as Nigaki, Quassia or Shurni has been discovered recently in the Harris Garden. This tree is very rare in cultivation. Other specimens are known only in the UK's most prestigious gardens and arboretums such as Kew, Wakehurst Place and Westonbirt.
The tree, more formally known as Picrasma quassioides was discovered by Ronald Rutherford, ex member of staff from the University's Herbarium and Rupert Taylor, the University's Assistant Grounds Manager with specific responsibilities for arboriculture. Although rare in the UK, it is widespread in the wild, occurring in Northern India, Nepal, Bhutan, China, Korea and Japan.
The genus belongs to the Simaroubaceae (perhaps best known for Ailanthus altissima, the suckering Tree of Heaven) and contains eight species. The related Picrasma excels is the source of quassia chips, formerly used in bitters and insecticide. Thus, our tree has been much studied chemically as it also contains many interesting compounds, including quassinoids and β-caroline alkaloids, the latter with known anti-viral properties.
The tree itself is upright and has attractive alternate, pinnate leaves, each with a terminal leaflet. Umbels of small bowl-shaped green flowers are followed by pea-sized succulent fruits which turn red when ripe. However, the glory of the tree lies in its autumn colour when the leaves turn yellow, orange and then scarlet, resulting in the botanist Sargent declaring: "Few Japanese plants I saw are as beautiful as this small tree".
The drawback appears to come in the Flora of China account that describes the tree as dioecious, ie. trees are either male or female. Our specimen is a female, so perhaps we need to try and acquire a male one to keep it company and enable it to set seed!
Why not spend a lunch break discovering 25 of the rarest trees on campus with the University's tree walk guide?
http://www.reading.ac.uk/fmd/Grounds/FMDGrounds_Tree_Walk.aspx