Toona (Endl.) M. Roem.

Toona belongs to the mahogany family, Meliaceae, but, unlike most species in that usually tropical family, it is deciduous. Few Meliaceae are familiar to temperate gardeners, Melia azedarach L. being a notable exception, but their timber is, or has been, of great importance in global commerce. Mahogany, from Swietenia in the neotropics, and khaya or sapele from the African Entandrophragma, are good examples. A few have edible fruits valued in tropical Asia, such as langsat and duku (apomictic cultivars of Lansium domesticum Corrêa) and santol (Sandoricum koetjape (Burm.f.) Merr.).

The family Meliaceae is allied to Sapindaceae, Rutaceae, Anacardiaceae and Simaroubaceae (which includes Ailanthus, with which members of the genus have often been confused), many or most of which, like Meliaceae, are tropical trees with pinnate leaves. Meliaceae differ in having a very distinctive set of chemical defences against insects, azadirachtin from the Neem tree (Azadirachta indica A. Juss.) of Asia being the most potent of known natural pesticides – even locusts are deterred. Slightly worryingly, neem extract is also used in some commercial toothpastes, while many other Meliaceae extracts are important in local medicine.

Toona comprises some five or six species from south Asia to the western Pacific, often difficult to distinguish from one another in the absence of both flowers and fruits, though T. sinensis (also known as Chinese Toon, Red Toon, Chinese Cedar or Chinese Mahogany, etc. etc.) is readily recognisable because of its usually toothed leaflets and obnoxiously pungent bark, besides its seeds being winged at one end, unlike other Toona species where the seeds are winged at both ends.

The most recently described (2015) species is Toona calcicola Rueangr., Tagane & Suddee, restricted to limestone in Thailand and unique in bearing erect inflorescences, like those of Cedrela odorata, but perhaps the most famous toon is T. ciliata, which grows naturally from Afghanistan and India to eastern Australia, where it is known as Red-cedar. Heights to 60 m and bole diameters to 3 m have been recorded. In 1803 it was scientifically named Cedrela toona, the specific epithet being from its Hindi vernacular name, tun, cognate with the Sanskrit tunna. It is grown as a street tree in India and its insect-resistant timber has been heavily exploited there, as it has in Australia, for house and boat building, particularly used for doors, mouldings and furniture (and coffins) in Australia in the nineteenth century (McPhee 2004), but also for tea chests, musical instruments and even pencils. In Australia it has been largely worked out. The foliage is used as cattle fodder in India, where flowers have been used as sources of red and yellow dyes; as with many other Meliaceae, extracts have been used in local medicines almost throughout its range.

The genus Toona was separated from Cedrela in 1846, though it is not unusual to still find T. sinensis referred to in horticulture and literature (e.g. Bean (1976) as Cedrela sinensis. Cedrela is a neotropical genus of 19 species, differing most strikingly from Toona in that their similar woody capsules have seeds attached to the lower part of the middle of the fruit whereas in Toona they are attached at the apex. Nonetheless, the two genera are closely related and the Trans-Pacific distribution of this pair is difficult to explain away in terms of current biogeographical orthodoxy (Heads 2019). The first described true Cedrela was C. odorata L., now CITES-listed but naturalized in the Mediterranean, as on Stromboli for example, and invasive in tropical Africa as well as the Galàpagos. Its timber is still used in rather characteristic cigar boxes, but also mothproof chests, the wood yielding gedunin, an antimalarial also found in Chinese Toon, as well as in Neem.

It is often confusing to those from the north temperate regions to find tropical trees and their timbers referred to as ‘cedar’ (as in Australia with ‘Red-cedar’ for Toona ciliata and ‘White-cedar’ for Melia azedarach), when that word is from the Greek kedros via Latin cedrus and Old French cèdre, of course referring to the wood of the coniferous Cedar of Lebanon (Cedrus libani). By the seventeenth century, though, similarly aromatic, but tropical, timbers were being called Cedrus, as in the 1690s name ‘Cedrus barbadensium…’ which was to become Cedrela odorata, the new generic name reflecting that superficial similarity (Mabberley 2004).