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Natural
History Big-Leaf Maple (Acer macrophyllum) Richard Hebda INDEX for Native Plants This text was originally published in Coastal Grower (formerly The Island Grower) in Victoria, British Columbia. For subscription information, please call Susanne Steele at the Coastal Grower at 250-478-0825. We have long recognized the vital role of shade trees in creating a pleasant environment around our homes. Most shade tree species and varieties hail from distant regions and lands. British Columbia is home to one of the most noble, but for some reason little used shade trees, big-leaf maple. Big-leaf, broadleaf or common maple grows as a tall spreading tree to 30 m (100') high, casting filtered shade beneath. In undamaged trees, the widely spreading root system supports a short trunk 2-5' across, from which reach out great limbs. However many trees have been cut, and hence grow as groups of tall greyish sapling stems. Old branches are bedecked with colourful mosses, leafy and crusty lichens. Young twigs are a pleasant medium green. Fat green buds end the branches during the winter. Leaves of big-leaf maple are the largest of any tree in British Columbia. Their form is typical for maples; three to five sharply-tipped lobes with deep indentations between. In spring the leaves begin soft yellow green in the sun's light and soon expand to full size some more than 30 cm (12") across. In fall their rich yellow forms paint each tree, then fall to earth to be crunched underfoot. The 10-15 cm (4-6") long flower clusters rival any in the genus. They burst forth in early spring revealing often 50 or more small greenish yellow fragrant blooms. Male and female flowers are separate, but occur in the same cluster. Each flower consists of petal-like sepals, and five petals which surround either a group of long spindly stamens or a two-parted ovary with two stigmas. The clusters magnetically draw pollinating flies until each tree hums like a giant machine. Fruits are rather large, typical maple keys consisting of a wing and body. The spiny hairs, which cover the surface of the body, will penetrate and irritate the skin. In British Columbia the maple's natural range includes most of Vancouver Island and the adjacent mainland coast, extending well up major valleys. Big-leaf maple is reported from Alaska, but the main distribution extends mostly west of the Cascade Mountains south to California with an outlying population in Idaho. Big-leaf maple revels in moist rich soils especially along rivers, streams and floodplains. Curiously you will find it on moist rocky slopes often rooted in the rubble at the foot of cliffs. The tree also thrives in disturbed settings along roads and fence rows. Although some authors consider big-leaf maple of little horticultural value, it makes an outstanding shade tree. The airy canopy produces light, rather than oppressive shade. Once the leaves fall, weak but welcome winter sunlight can penetrate into the home. Because of its size, this maple may not suit sophisticated urban gardens, but it cannot be beat as a huge specimen tree for a large yard, park or street planting. You can easily raise maple trees from seeds planted in ordinary soil. Often, hundreds of seedlings struggle to survive under majestic parent trees. These seedlings transplant easily in the moist winter and spring. You may have a problem growing a traditional flower garden below the thirsty tree. Native species such as salal (Gaultheria shallon), Oregon Grape (Mahonia spp.) and sword fern (Polystichum munitum) will thrive in its shade. Big-leaf maple wood found many uses among our coastal Native Peoples. From it they made dishes, spoons, rattles, bark shredders adze handles and numerous other tools. The wood is perhaps best known for the carving of beautiful spindle whorls and canoe paddles. Many aboriginal peoples valued the wood as a fuel, for it burns hot and clean. Big-leaf maple is an excellent fuel tree today too, because it can be cut to harvest the firewood and re-sprout fresh new suckers for future wood production. Well managed root systems and stumps could yield firewood for many decades. Natives used the bark to weave ropes and baskets. Leaves were spread over and under food in steam pits and picking baskets. Incidentally people have tried to make syrup from spring sap but apparently the sugar concentrations are too low and the day-night temperature changes too slight for a good flow. The scientific name Acer is the same as the classic Latin name for maple. The species name "macrophyllum" celebrates the trees most obvious feature, the big (macro) leaves (phyllum). Looking for a shade tree or an excellent permanent firewood source, try our native big-leaf maple. This under-appreciated native species deserves to be more widely grown. For more information on native species please visit our Native Plant Garden, or contact Richard Hebda at the Royal British Columbia Museum.
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