Douglas Justice, Associate Director of Horticulture and Collections, shares both his photographs and writing skills today. He scribes:
I had the distinct pleasure of visiting the Royal Botanic Gardens, Kew the other day. I spent most of a day wandering, familiarizing myself with many unfamiliar species, and rediscovering a number of remarkable specimens. Something I hadn’t noticed on previous visits was a stately Chinese mahogany. As mature trees of Toona sinensis are rare in Vancouver, I took a number of pictures. I thought it would be a good addition to the images we’ve already compiled for the soon-to-be-released app, Vancouver Trees. Building on that here, I’ve included an excerpt from the text on Toona sinensis.
Toona is a small mostly tropical genus in the mahogany family (Meliaceae), with species native from western Asia to Australia. All mahoganies are tall trees that have large, spirally arranged, pinnately compound leaves and tiny flowers borne in often huge, pendent inflorescences. The trees are prized for their high quality timber, but most species are now scarce because of overcutting in their native ranges.
Toona sinensis, which was previously known as Cedrela sinensis, is native to much of temperate and tropical Asia and is the northernmost species in the family. It is a large, spectacularly handsome deciduous tree, capable of growing 40 m or more tall in the wild and developing a buttressed trunk like that of large tropical hardwoods. In cultivation here [in Vancouver], Chinese toon, which is also known as Chinese cedar or Chinese mahogany, grows to about 15 m tall. Trees are famously variable–subtle variations in leaf shape, size, colour and hairiness are so common in the wild that eight named variants of this single species have been recognized by Chinese authors. The most common variant in cultivation, which is represented locally by the Australian cultivar ‘Flamingo’, displays shoots that emerge brilliant scarlet and expand to bright shrimp pink before turning green. Less flamboyant seedling plants are also cultivated, but all tend to display reddish or bronze purple new growth in late spring. Foliage generally becomes light yellow-green by mid summer and in autumn turns yellow before the leaves fall. In China and Indochina, the new shoots of Toona sinensis are used as a cooked vegetable (the redder, younger shoots being the tastiest, or at least, the most sought after) and in South Asia the mature foliage is used for animal feed. The bark and roots of trees are widely used in folk medicine. It is the only mahogany that can be successfully grown in the Vancouver area.
Toona sinensis may be confused [locally] with Ailanthus altissima on account of its large, tropical looking pinnate foliage, but tree of heaven leaves are malodorous (not the bark and wood) and the leaflets are broader and more conspicuously asymmetric, often with a basal lobe to one side. Other possible confusions are with bitter ash (Picrasma) and walnuts (Juglans), but the largest leaflets in the pinnate leaves of Picrasma are closest to the tip, and in Juglans species they are in the middle of the leaf. Like Chinese toon, walnut trees are somewhat aromatic, but the aromatic compounds in walnuts are mostly sweet smelling alkyl-aldehydes (e.g., the aldehyde hexane, which is a common constituent in Juglans tissue, smells of freshly cut grass), whereas sulphur compounds are responsible for giving Toona its peculiar aroma. In flower, Toona displays pendent, airy clusters of small, cream-coloured unisexual flowers, but these are produced only on mature specimens in mid summer. Small capsules follow, but the copiously produced winged seeds do not appear to be viable without cross pollination. The names toon and Toona are probably derived from the Chinese name, xiang chūn (literally, tree vegetable).