ALONG with all the innumerable shades of green there are other leaf colours – fleeting or permanent, subtle or sensational – that enrich the garden scene. Copper, bronze and rust come and go through the year; gold may be fixed or fleeting, but silver remains as a permanent sparkler.
STERLING SILVERMost silvery leaves are those covered in fine hair or wax as protection, usually against sunburn and moisture loss in hot environments. Many downy leaves are soft and woolly with a matte finish, but in some the fine hairs lie flat and create a beautiful sheen on leaves that range in colour from pewter to steel blue to gleaming silver.
In hot, bright sun, waxy bloom becomes thicker and the leaf paler.
In shade the bloom may disappear completely, exposing the darker green in the leaf itself.
Silvery stars include Convolvulus cneorum, a twinkling little shrub with white flowers and steely blue leaves, sterling bearded irises and Table Mountain’s beautiful silver tree, Leucadendron argenteum.
There are other silvery leaves adapted in a different way to the low light of the forest under-storey. Their sheen, almost iridescent and usually in a variegated pattern, is produced by their epidermal cells.
Botanists have described them as providing “some unknown adaptive advantage for life in deep shade”, perhaps helping the absorption of light, or as disruptive colouration, ie camouflage, to confuse leaf-eaters. Whatever the reason, these are the most beautiful and curious of leaves, most often enjoyed beyond the jungle as indoor plants such as begonias (Begonia rex), painted ferns (Athyrium and aluminium plants (Pilea).
GOLD LEAFPermanent gold may be uniform greeny gold, as in specially selected or bred cultivars of all kinds of plants from herbs to trees such as the famous Melaleuca “Johannesburg Gold”, but more often it shines in variegation.
Variegated plants, especially the more boldly marked and brightly coloured ivies, coprosmas and euonymus are not as popular as they once were, but they can still play a valuable role in brightening up shady areas.
Aucuba japonica, with its dainty gold stippling and obliging nature, remains a stalwart for shade.
Transient gold is at its brightest in new leaves and catkins, for example, in our white stinkwood (Celtis africana) – one of the joys of spring – and in autumn grasses and leaf colouring.
Purest autumn gold of all is the maidenhair tree (Gingko biloba), which has unique fan-shaped leaves that turn a beautiful clear yellow.
This fascinating tree from China is possibly the oldest of all tree species, closely resembling fossils from the Permian, 270 million years old.
All kinds of healing powers have been attributed to it and it’s also able to absorb pollution and so has become a popular tree for city planting.
COPPER & BRONZE These lovely shades come and go in buds and leaves throughout the year and are always a subtle element in the richness of the garden scene.
So many new leaves emerge as copper or bronze; in classic shrubs such as Indian hawthorn (Raphiolepis indica), and Photinia Red Robin and the beautiful indigenous red-leaved rock fig, Ficus ingens.
Abelia grandiflora is another superb shrub with copper-tinged leaves and pure copper calyces. And the indigenous lavender fever berry (Croton gratissimus) is full of bronze and copper lights from its stems and bronze-backed leaves.
AUTUMN COLOURAutumn colour varies from year to year. As days begin to shorten and temperatures fall, deciduous plants begin to draw nutrients from the leaves to store for hibernation. So the green pigment disappears leaving the orange and yellow pigments exposed.
At the same time, there may be a build-up of anthocyanins, which add blue and purple pigments, combining with the yellow and orange to produce copper, bronze, plum and red. Brilliance depends on the species of tree and the right combination of soil moisture, cold nights and mild dry days – late heat shrivels the leaves before they have time to colour.
Excellent indigenous trees for autumn colour that are also suited to smaller gardens include the graceful lavender tree (Heteropyxis natalensis), which has pale grey bark and leaves which turn a rich red in autumn. The mountain seringa (Kirkia wilmsii), which grows to seven metres, has feathery foliage which turns fiery red and gold. Pay a visit to your nearest indigenous specialist to see how many other beautiful trees and shrubs are colouring the scene this month. © Home Weekly