In Sunnyside big-leaf maple and black cottonwood [poplar]are the dominant deciduous species in the Forest along with the smaller alder, mountain ash, western birch, dogwood, and cascara.
The aptly-named big-leaf maple is the largest of the maples reaching up to 35m in height and 60 cm diameter. The large 5-lobed leaf, up to 35cm across, is deeply indented and the grey-brown bark of older trees, which is markedly furrowed, retains moisture more than other species so that it is often covered by mosses, lichens and ferns. Its range in B.C. is limited to the south-west corner and southern Vancouver Island.
Black cottonwood is a tall, (up to 50m) cylindrical light-crowned tree growing vigorously on moist or wet sites. Leaves are egg or heart-shaped, with fine marginal teeth and an elongated pointed tip. The twigs and buds are fragrant and resinous. The largest of the cottonwood or poplar species group it regularly interbreeds with its balsam poplar relative. The name, cottonwood, derives from the fine white hairs which surround the abundant seeds and aid in wind-blown dispersal.
Red alder is a widespread mid-sized but short-lived tree. It can have a single, branchy-stemmed trunk or several bushy stems depending on where it is growing. The toothed leaves are coarse-textured, dull green with hairy veins on the underside. They remain green in winter. Alder is a pioneer species readily occupying disturbed sites where it’s nitrogen-fixing property is a valued soil-improver. Freshly cut wood is yellowish but it soon turns red when exposed. It burns well.
Mountain ash [rowan to any Scot] occurs scattered through the Forest. It’s a smallish tree rarely more than 4m tall. It has a distinctive compound leaf made up of 7 to 11 sharp-pointed leaflets and bright red berry-like fruits favoured by many over-wintering birds. The narrowly-conical dark-brown buds are sharp-tipped and sticky.
Paper Birch is variable in form most commonly slender stemmed with a light open crown. Leaves are triangular, partially toothed, green above, pale and hairy on the underside. The bark peels readily and has many uses including a form of chewing gum amongst native residents.
Young trees can easily be confused with bitter cherry.
Cascara an erect small shrub or small tree, is present but not at all common in the Forest. Its bark is smooth, grey and bitter tasting. The single, evenly-toothed leaves are oblong or egg-shaped, smooth on the upper side hairy below and with 6 to 8 pairs of veins. Buds are sticky. The yellowish inner bark darkens when exposed to light and air. An infusion of the bark is strong laxative.
Dogwood B.C.s provincial flower, is present but rare in the Forest. The opposite leaf pairs are dark green, about 10cm with characteristic venation. The showy ‘flowers’ are in fact modified leaves or bracts surrounding small clusters of true flowers. The bark is smooth and grey.