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A deciduous tree up to 150 ft high in the wild, but not much more than half as high in England. It has a straight, erect trunk, with slender branches forming (as the tree is usually seen in this country) a narrow, pyramidal head. Branchlets glabrous and round at first, but during their second year they turn grey, and often begin to form corky wings after the fashion of the English elm, but in some trees the branchlets remain quite smooth. Leaves maple-like, usually five- sometimes seven-lobed, 5 to 7 in. wide, scarcely as long, heart-shaped at the base, the lobes minutely toothed, ovate-lanceolate; upper surface glabrous and glossy, the lower one with tufts of hair in the axils of the veins; stalk slender, 21⁄2 to 4 in. long. Male flowers in small round heads arranged on a downy spike 2 or 3 in. long; female inflorescence rather larger, 1⁄2 in. wide. Seed-vessels in a roundish cluster 1 to 11⁄2 in. across.
Native of the eastern United States, often in swampy ground, and also of Mexico and Guatemala. It was introduced in the 17th century, and has long been valued for its stately form and handsome foliage. It is often mistaken for a maple, but from all maples is, of course, distinguished by the alternate leaves. In autumn its foliage turns to shades of purple, crimson, and orange. The tree produces a fragrant resin, known as ‘sweet gum’. The timber, although not of first quality, is largely imported under the name of ‘satin walnut’, for furniture making. Under cultivation it likes a good deep soil, and a moderately moist but not a swampy position.
The largest tree at Kew, situated in the Liquidambar collection, measures 90 × 7 ft (1965) and there is a smaller specimen of 62 × 43⁄4 ft by the Clematis wall (1967). At Syon House the largest is 93 × 83⁄4 ft (1967); this was about 75 × 6 ft in 1904. Others near London are: Mote Park, Maidstone, 82 × 53⁄4 ft, and Linton Park, Maidstone, 85 × 6 ft (1965), both superb trees, the latter with a 45-ft bole; Royal Horticultural Society Garden, Wisley, Surrey, 72 × 61⁄2 ft (1964); Knap Hill nurseries, Surrey, 69 × 8 ft (1962); Lydhurst, Sussex, 69 × 33⁄4 ft (1965); Stratfield Saye, Hants, 87 × 9 ft (1968). Farther west the most notable specimens are: Escot, Devon; 74 × 93⁄4 ft and 90 × 7 ft (1965); Arley Castle, Worcs., 72 × 5 ft (1961); Westonbirt, Glos., in The Downs, 67 × 71⁄4 ft (1967).
specimens: Kew, by the former Clematis Wall, 60 × 51⁄4 ft (1981); Syon Park, London, 100 × 91⁄4 ft (1982); Osterley Park, London, 92 × 53⁄4 ft and 80 × 73⁄4 ft (1982); Ebernoe House, Northchapel, Sussex, 72 × 7 ft (1983); Knap Hill Nursery, Surrey, 82 × 83⁄4 ft (1974); The Rookeries, Dorking, Surrey, 95 × 7 ft (1983); Lydhurst, Warninglid, Sussex, 77 × 41⁄4 ft (1980); Buxted Park, Sussex, 87 × 61⁄2 ft (1978); Linton Park, Kent, 87 × 63⁄4 ft (1984); Stratfield Saye, Hants, 95 × 10 ft (1982); Westonbirt, Glos., 65 × 73⁄4 ft (1977); Escot, Devon, 85 × 6 ft (1982).
Raised from seed, the sweet gum is unreliable in its autumn colour and also of unpredictable habit. Two British-raised clones colouring well are: ‘Worplesdon’ (Messrs Jackman) and ‘Lane Roberts’ (Messrs Hillier). Others have been selected and named in Australia, New Zealand and the USA, but these are as yet untested in this country
There is some doubt about the correct nomenclature of the variegated clones. As the Hillier Manual has it, in ‘Aurea’ the leaves are marked with yellow and colour well in autumn; while in ‘Variegata’ they have a creamy white margin and a grey and green centre.
As noted on page 583, the sweet gum is also a native of Mexico and Guatemala. It is in fact one of a contingent of woody species that have their main home in eastern North America, but appear again after a wide gap in the cloud-forests of the Sierra Madre del Sur. Seed was collected in 1983 by J. R. Russell at Jalapa in Veracruz State, where it forms forests at 4-5,000 ft, with Carpinus caroliniana, Ostrya virginiana and Nyssa sylvatica, and is almost evergreen.