Acer pennsylvanicum. Killerton, Devon. This small maple from eastern north America is a 'snake-bark' with attractively striped stems. The rather large leaves have shallow acuminate lobes and colour yellow in autumn. There are some interesting variants with differently coloured stems (next).

Acer pennsylvanicum 'Erythrocladum'. Bodnant, Wales. Winter stems of a beautiful coral-red.

Acer platanoides, Norway Maple. Kew, UK. This very familiar medium-sized to large tree with a spreading crown is native to most of temperate Europe, although not the UK. It is a much more attractive tree than the sycamore, A. pseudoplatanus, although perhaps not quite so tough, and although it self-sows readily is not so invasive as its relative.Norway Maple is a much more attractive tree than sycamore with better autumn colour, and if a large tree is required should always be chosen in its place.

Acer rubrum. Canadian Maple. Bodnant, Wales. This small to medium tree from eastern north America varies between its selections, not all of which necessarily colour red.

Acer rubrum 'October Glory' is perhaps the best of the varieties of Canadian Maple which colour red in autumn. 'Autumn Glory' seems to be the same variety. Kew, UK.

Acer rufinerve. Kew, UK. A Japanese 'snakebark' closely related to A. capillipes and A. davidii, with the same green stem striped white, but with rather more lobed leaves with acuminate lobe tips. Usually colours a clear yellow in autumn.

Acer sieboldianus. Kew, UK. A relative of A. circinatum, but from the far north-east of Asia, and colouring a fine orange-red in cultivation, this rather rare small tree deserves to be grown more often.

Most forms of Acer tetramerum are not renowned for their autumn colour, but they have attractive reddish branches in winter and red flowers and coloured shoots in spring. The leaves are rather small and entire, ovate-lanceolate with an acuminate tip. It is sometimes used as a street tree. China. Photographed at Kew, UK.

Acer triflorum is another rare small tree from north-eastern Asia, Manchuria and Korea, which has excellent autumn colour. Wisley, UK. The greyish flaking bark reveals its relationship to A. griseum.

Acer triflorum, foliage. Leaflets are usually in threes and are bluntly toothed, but are more acute than in A. griseum..

Acer velutinum, Velvet Maple is a relative of sycamore, A. pseudoplatanus, but with downy leaves and often more attractive autumn colour. It can be a large tree, to 40 m. Iran, Azerbaijan and Georgia. Kew, UK.

Acer x conspicuum 'Phoenix'. One of several named varieties of this intercontinental cross between the American snakebark A. pennsylvanicum and the Chinese A. davidii. All have attractively coloured twigs in winter. the variety 'Flamingo' is perhaps the best known and is well suited to a small winter-themed garden.

We finally leave the great genus Acer, maples, and move on to Aesculus, the horse-chestnuts and buck-eyes. This is an old and rather primitive genus of trees and shrubs which has a scattered distribution throughout temperate regions of the northern hemisphere, although the greatest diversity is found in north America. Species are known for their beautiful, insect pollinated flowers borne in vertical racemes, and the fruits which contain one or two very large seeds ('conkers', or 'buck-eyes'). On the whole the genus is not noted for its autumn colour, but Aesculus flava, the Sweet Buckeye, pictured above, turns a lovely orange in the fall. It is native to the SE USA, but here is pictured at Kew, UK. It can grow to quite a large tree and has yellowish flowers.

Aesculus indica is native to the north-western Himalaya. Typically it has reddish flowers, and readily hybridises with the Horse-chestnut, Ae. hippocastanum to give rise to widely grown cultivars with pinkish flowers. Often the autumn colour is no better than in the Horse-Chestnut, but the variety 'Sydney Pearce', with white, yellow and pink-spotted flowers, shown here at Kew, usually colours a good dark yellow.

Aphananthe aspera is a Chinese (to Korea and Japan) relative of the elms. It forms a medium-sized tree which is often used for timber. It is not renowned for its autumn colour, but can turn a pleasant yellow, as here at Kew, UK.

Aralias are tree-like relatives of ivy with multiple woody stems to 10 m or more and large panicles of ivy-like flowers, borne in late summer. Aralia elata, the Japanese Angelica tree is often grown both for its flowers and for its excellent autumn colour. Howick, Northumberland, UK.

Aralia elata, Blaydon Burn, UK. There are excellent variegated forms of this species, notably 'Aureo-variegata'.

Aronia melanocarpa, the Black Chokeberry is an excellent medium-sized shrub for autumn colour. A member of the Rosaceae, related to Pyrus and Sorbus, it is native to eastern North America. The white Crataegus-like flowers are followed by shining black berries. Howick, Northumberland, UK.

Berberis thunbergii is a Japanese barberry, all forms of which have excellent red foliage for several months in autumn. Often the slender red berries are almost the same colour. The plant pictured (author's garden, UK) is one of the green-leaved varieties.

Berberis thunbergii 'Atropurpurea'. This fine prickly shrub has pendant yellow flowers which contrast well with the purple foliage as it emerges in spring. It can grow to 4 m in height, but withstands heavy clipping and forms an excellent hedge if so treated. Wisley, UK.

Betula ermanii. Author's garden, UK. Birches do not on the whole produce the most exciting autumn colour, but there are forms of Asian species that colour well, and B. ermanii from Korea to Manchuria is one of the best examples. However birches are extremely important in the autumn garden for their barks and boles.

A young tree of Betula ermanii with good yellow autumn colour. Howick, Northumberland, UK.

Most Betula ermanii have good boles, but those of 'Grayswood' are simply superb with a smooth pinkish hue. The Garden House, Devon, UK.