Photo copyright © 2020 Mariposa Native Plants
A large native deciduous tree, with big green leaves in the spring and summer, often turning to bright golden yellow in the fall. This maple grows quickly and can get over 100 feet high. Careful consideration should go into selecting a site for the tree. Typically, in Mariposa County, however, Bigleaf Maples tend to top out at 50-60 feet.
Photo copyright © 2020 ariposa Native Plants
A close-up of A.macrophyllum in the early fall, with its lower leaves just beginning to yellow. These leaves are approximately 8 inches (20 cm) across. On some Bigleaf Maple trees, the leaves can be as much as one foot in diameter.
A.macrophyllum is found all along the Pacific coast from British Columbia through Washington and Oregon, into California, and down into Baja California. In southern California, it can be found in the Angeles and San Bernadino National Forests, in the Cleveland National Forest, and even into the Cuyamaca Mountains. It also occurs along the western slope of the Sierra Nevada almost as far south as Bakersfield. In Mariposa County, it's a bit rare, but you can find it in Yosemite Valley. Also, look for specimens in the Ponderosa Basin area and up into the adjacent mountains. There was a nice grove of A.macrophyllum in the Snow Creek drainage of Mariposa County, around the intersection of Triangle Road and Darrah Road, but this area burned during the Oak Fire event of 2022. Elevation: sea level to 9,000 ft. (2700m). Sun: full or partial. Temperature: cold tolerant to 5°F (-15°C). Soil: clay or loamy soil, preferably near a stream or well-watered arroyo; soil pH 5.5-7.5.
Fairly easy to care for once established. Needs a site that has moderate moisture, such as near a stream. If it's planted away from a natural water source, it should be watered regularly during the summer to maintain soil moisture. Roots are sensitive to disturbance; avoid breaking the root ball when planting from the container. If the plant is root-bound in the container, with roots circling the bucket, try to separate some of the larger roots and direct them away from the trunk of the tree in the hole. Water a tree from a #1 container with 1 gallon (4 liters) once per week until the first winter. Stop watering after the first good rain. Water once every two weeks, same amounts, in the second summer. Thereafter, simply maintain soil moisture. If the tree is from a #2 container, the same regimen applies, except double the water amounts. A.macrophyllum grows quickly, a couple feet per year, and can become a large tree. This might be what you want--summer shade and all--but don't locate it right next to a structure; plan your site accordingly.
Lower mountains (2500-3500 feet), middle mountains (3500-6000 feet); A.macrophyllum might be a deciduous tree choice near a watercourse in the foothills, but be prepared to supply summer water.
Photo copyright © 2020 Mariposa Native Plants
A.macrophyllum is the host plant for almost a hundred moths and butterflies, including the Polyphemus Moth (Antheraea polyphemus), the Mourning Cloak butterfly (Nymphalis antiopa), and the Western Tiger Swallowtail butterfly (Papilio rutulus).
Pathogen unknown: Beginning about ten years ago, reports emerged about die-off of Bigleaf Maple trees in Washington and Oregon. The symptom is a reddening of the outer leaves, followed by the death of the tree's crown and then the death of the rest of the tree. There has so far been no conclusive determination as to the cause of the die-off, but it does not seem to have penetrated too much into California--at the present time.
Gophers: Might eat at the roots of A.macrophyllum; if you have a gopher population under your landscape, consider using a gopher cage beneath the young plants. Also: try to control the gophers!
Deer: Do not seem to browse on Bigleaf Maple, but it could be prudent to surround newly planted small trees with a modest deer screen, about 4 feet high, enough to cover the tree over its height, anchored with firm stakes, so that the deer cannot easily nibble on the young leaves.
Where appropriate, this tree is particularly beautiful to the aesthetically-inclined native plant gardener. It provides abundant summer shade, winter sun through its naked branches, and--well, yes--at lot of yellow leaves on the ground beginning in the fall.
#1 container, about 1 gallon
Deep tree pot, about 1 gallon
#2 container, about 2 gallons