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Steven L. Schulz: Maple trees of North America largest on earth
In the garden with Steve

Steven L. Schulz: Maple trees of North America largest on earth

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Acer macrophyllum, known as bigleaf maple or Oregon maple, is a large deciduous tree native to Western North America, and dons the largest leaf of any tree in North America — and the largest of all 128 maple species on earth. 

The largest bigleaf maple on record stood 158 feet tall, had a canopy spread of over 90 feet and had a trunk diameter of 8 feet.

Description: Acer macrophyllum trees range from 50 to 80 feet tall with a domed canopy 30 to 50 feet in diameter. The branching pattern is fairly open producing a soft shade which allows for moderate understory growth.

Bigleaf maple leaves are palmate with five deeply incised lobes and range in size from 6 to 12 inches across, or larger. Leaf margins of the sharply pointed lobes have irregular coarse teeth with blunted tips. The Leaves are dark green and shiny on the upper surface and paler and matte beneath.

The leaf petioles are as long as the leaf and arranged in opposite pairs along the branches. The foliage turns yellow/gold in autumn with the brightest colors in areas with freezing winter temperatures.

The flowers of Acer macrophyllum are a pendulous raceme 4 to 6 inches long, with up to 60 pale yellow/green flowers. Flowering occurs in March and April when the tree comes out of winter dormancy.

The raceme consists of both male and female flowers, but trees can produce only male or female flowers on any individual raceme.

Bigleaf maple seeds/fruit is a two winged samara ½ inch in diameter with wings up to 2 inches long.

Habitat: Acer macrophyllum is commonly found along coastal streams and rivers from Southeast Alaska to Southern California. It is also found in the foothills of the Sierra Nevada and Cascade mountain ranges and a small colony in central Idaho.

It prefers moist well drained soils of riparian habitats but can be found in poor rocky soils around springs and seeps. Mature trees can withstand seasonal flooding without damage.

Bigleaf maples are found in mixed evergreen forests, Oak woodlands and canyons of coastal chaparral.

Acer macrophyllum seedlings and saplings have a high mortality rate due to frequent browsing by deer. A university study in Oregon found that over 60% of seedlings 1-foot tall had been browsed, many of them several times.

Uses: Bigleaf maple is the only commercially important hardwood maple in the Pacific Northwest. The wood is moderately hard, fine grained and pale brown in color, and is prized by makers of musical instruments for its tonal qualities and durability. The wood is also used in furniture, kitchen utensils, and veneer for paneling.

Acer macrophyllum can also be used to make maple syrup where winter temperatures drop below zero degrees. The sugar content of the spring sap is the same concentration as the Sugar Maple—Acer saccharum, but the flavor and aroma are slightly different.

Steve Schulz is one of the initial founders of the Santa Ynez Valley Botanic Garden and currently serves as the garden coordinator.


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