As the weather cools in late summer and the days shorten noticeably so the deciduous trees and shrubs begin to withdraw chlorophyll from their leaves in preparation for the winter shutdown. With less of that vital green pigment to mask them, the other colours within the leaves begin to show through.
While the best of the autumn color may be over for this year, the coming winter months are the time to consider how best to prepare for next years autumn glory.
When it comes to the most vibrant tones, the genus Acer, the maples, includes many sterling contributors. Most of the 150-odd species of maples are deciduous trees, though some are shrubby and a few are evergreen. Acer is primarily a temperate northern hemisphere genus, ranging from around 59?N southwards to the mountains of the subtropics. With the exception of a few Eurasian species, principally the Norway Maple (Acer platanoides) and the Sycamore Maple (Acer pseudoplatanus), most of our garden maples are derived from Asian and North American species.
Maples do flower, but apart from a few with showy tassel-like blooms, most are grown solely as foliage plants, And while the thrust of this article is about autumn colour, many of the best autumn maples are also excellent spring and summer foliage plants.
Of course, getting good autumn colours depends greatly on the climate and the shades vary from year to year even in districts known for their autumn foliage. Generally the best colours develop during a prolonged autumn with warm, still days and cool but not freezing nights. Soon after the first frosts strike the last leaves fall.
Although most maples colour to some extent in autumn, the following species and their cultivars are readily available and among the brightest and most reliable.
This 10-12 m tall, round-headed tree eastern China and Japan gets its common name from the leaves, which usually have three lobes. The leaves are small and primarily red in autumn, with tints of orange and yellow.
Found from the Caucasus to northern India, broad-crowned, 15-20m tall tree is best known for its bright golden yellow autumn foliage. Cultivars include 'Aureum', with yellow foliage in spring and autumn, and 'Rubrum', which has bright red young stems and spring leaves.
Best known for its white-striped and flecked green to purple bark, this 15 m tall Chinese species has 3-lobed or unlobed leaves that often colour brilliantly in red, gold and orange tones before falling. 'George Forrest' is a large-leaved cultivar.
Again, best known for its bark, which is warm brown and peeling, the foliage of this 5-10 m tall Chinese tree turns bright red in autumn. Because of the red-brown bark, the foliage colour can seem muted and is perhaps best seen at a distance where the colour of the whole tree can be appreciated.
This slow-growing Japanese native is a small tree with tiered branches and 7-11-lobed leaves that can be almost round in some forms. The autumn colour is a combination of bright red and yellow on a green background. The Fernleaf Full-moon Maple, 'Aconitifolium', has very finely divided foliage reminiscent of aconite leaves.
The Golden Full-moon Maple (Acer japonicum var. aureum) has rounded lime green spring leaves that become yellow as they mature then turn golden and red in autumn. It is now more properly known as Acer shirasawanum 'Aureum'.
Everyone knows the beautiful Japanese maple with its seemingly endless range of cultivars in every imaginable leaf shape and colour. Originally found in Japan and Korea, it has been highly refined and developed by both Japanese and Western gardeners.
Regardless of its preference for cool, humid conditions and a tendency to develop die-back, the Japanese maple is nearly everyone's favourite small tree. The autumn foliage colour of the purple- or red-leaved forms is usually just a more intense shade of the summer colour, while those with green to pale gold leaves develop shades of red, orange, gold and yellow.
For autumn colour consider: 'Bloodgood', deep red; 'Aureum', deep gold; 'Beni Kagami', bright red; 'Hessei', red; 'Dissectum', bright orange; 'Dissectum Atropurpureum', red; 'Linearilobum Atropurpureum', bronze; and 'Linearilobum Rubrum' bright red.
Found from northern Europe to the Caucasus, the Norway maple is a strong-trunked, round-headed tree to 30 m tall, with 5-lobed leaves up to 18 cm wide. While the species has deep green leaves that rarely develop much colour before turning brown and falling, some of the cultivars offer brighter hues. 'Schwedleri', in particular, is a purple-green form that often reddens intensely in autumn. 'Goldsworth Purple' can develop similar tones.
Red, Scarlet or Swamp Maple
Native to the eastern United States, this fast-growing 20 m tall tree has 3-5-lobed leaves up to 10 cm wide that colour well in the autumn, developing intense red and gold tones. This species is occasionally tapped for its syrup. 'Columnare' is a broadly columnar cultivar, not to be confused with A. platanoides 'Columnare'. 'Red Sunset' has particularly good autumn foliage.
Often confused with the sugar maple because of their similar botanical names, the Silver Maple is found over much of eastern North America, grows quickly to around 40m tall and has an open crown. Its large leaves have silvery undersides and are red, orange or gold in autumn.
This species, widespread in North America, is both a timber tree and the source of maple syrup, which makes it the most commercially important maple. As it was the pattern for the maple leaf on the Canadian flag you might think it would have red autumn leaves. Well, sometimes it does, but it is very variable; sometimes red, other years orange, gold or combinations of colours.
Found over much of the temperate northern hemisphere outside Europe, this 10m tall tree has rounded, toothed leaves that turn vivid shades of yellow, orange and red in autumn. The Amur Maple (Acer tataricum ssp. ginnala), from Siberia, northern China and northern Japan, is shrubby, extremely tolerant of wind and cold and has red autumn foliage. It used to be classified as Acer ginnala, and is often still sold under that name.
Except for a few species, maples are generally very hardy. They prefer a deep, well-drained, fertile soil with plenty of humus. For the best autumn tones plant in a sunny position but try to provide good wind protection, at least for young plants and Japanese maples, or the foliage may burn or fall before it has a chance to colour well.
Maples respond well to light winter pruning when young and are best shaped to a fairly round crown on a sturdy trunk. Some, such as Acer palmatum, tend to be fairly shrubby with low forking and these are best left to develop naturally.
Even though the exact autumn shades are difficult to predict and will vary from year to year, you won't go far wrong with maples. They're beautiful enough in any season to forgive them their vagaries.
Did you know?
It takes around 43 litres of Acer saccharum sap to produce 1 litre of maple syrup. A good sized sugar maple yields around 50 litres of sap and during the processing into syrup the sugar concentration rises from 2% to 66%. No wonder it's so sweet, but what a flavour!
I am a garden book author and horticultural photographer based in Christchurch, New Zealand. I run a stock photo library called Country, Farm and Garden (http://www.cfgphoto.com). This article may be re-published provided this information is published with it and is clearly visible.