macrophyllum – from the Greek words macro (large) + phyllon (leaf), in reference to the huge leaves

Native range: Western British Columbia to Southern California

Leaves:

• opposite
• simple
• very large (6–12”; 15–30 cm)
• very deeply 3–5 lobed (middle lobe also 3 lobed)
• long petioles (almost as long as leaf)

Flowers:

• inflorescence – pendulous racemes
• 4–5” long
• yellow
• fragrant

Fruit:

• schizocarp
• hanging in long, cylindrical clusters
• spread at sharp V-shaped angle (<90 degrees)
• stiff yellow hairs on seeds

Other characteristics:

• tree to 90 ft.
• trunk usually split within 10 ft of ground
• branches of mature trees are massive, spreading, and steeply inclined at the tips
• deciduous
• flowers before leaves
• petioles have milky sap if split
• young bark green and smooth
• older bark grayish/reddish brown, interlacing ridges & furrows, often covered with mosses, lichens and small ferns.

Relevant info:

• lives 50-200 years
• largest maple species in North America, producing largest maple leaves in N. America
• most common Seattle tree
• called “paddle tree” in many First Nation languages because wood was used to make canoe paddles, among other implements

Ecology & Adaptations:

• native from Alaska south to northern California
• in Washington, both sides of the Cascades
• found in dry to moist soils, often with Douglas fir (Pseudotsuga menziesii)
• often on sites disturbed by fire or logging
• moist woods from sea level to mid-elevations in the mountains
• epiphytes (surface plants):
  • hosts more communities (by mass) of moss/lichen/ liverwort/fern than any other species in PNW
  • licorice fern (Polypodium glysyrrhiza), with licorice-flavored rhizome, is common epiphyte
  • epiphytes can form canopy soils into which the tree produces “canopy roots” (first discovered by graduate student who liked to climb trees!)
• pollination:
  • by insects including bees, flies, and beetles
  • trees resume growth early in spring and flowers bloom before or with leave emergence, which creates competitive advantage for attracting pollinators
• sexual reproduction:
  • heterodichogamous
  • within and among populations, trees may produce female flowers before male flowers (protogynous) or male before female (protandrous)
  • mating system facilitates outcrossing and genetic diversity
• seed dispersal:
  • ‘wings’ aid dispersal by wind
  • seedlings survive only if taproots reach moist soil before the dry season
• vegetative regeneration – re-sprouts from adventitious buds in root crown or stump after fire, cutting, or other disturbance
• tolerates flooding:
  • short-term but not long-term (>2 months) in riparian zones, in both lower and upper stream terraces
  • re-sprouts
  • large woody material is important part of floodplain log jams
• moderately shade tolerant, but photosynthesis is more efficient in full sun or edge conditions
• usually pioneer species establishing in open areas created by disturbance
• fire tolerant:
  • readily re-sprouts following topkill
  • thick bark on large, mature trees provides protection from fires of moderate severity
  • off-site trees may provide seed dispersed by wind
• tolerates wind – deep taproot
• succession:
  • in riparian communities, bigleaf maple often follows red alder (Alnus rubra) and willows (Salix)
  • turnover rate from red alder to bigleaf maple and black cottonwood (Populus trichocarpa) dominance ranges from 60 to 80 years
  • bigleaf maple and Sitka spruce (Picea sitchensis) may remain codominant “for centuries” before Sitka spruce overtops the hardwoods
  • on upland sites, maple may replace Pacific madrone (Arbutus menziesii) and oaks (Quercus)
• wildlife:
  • many species use bigleaf maple for food (mule deer, mountain beaver, rodents, invertebrates) and cover (mule deer, elk, creeping voles, Townsend’s chipmunks, western redbacked salamanders, and Pacific giant salamanders)
  • seeds are eaten by Douglas’s squirrels, northern flying squirrels, deer mice, finches, and evening grosbeaks eat the seeds
  • harlequin ducks and pileated woodpeckers nest in these trees
  • honeybees and other insects feed on the nectar