Practical ecological knowledge for the temperate reader.

Bigleaf Maple - Acer macrophyllum


"Acer macrophyllum is a deciduous Tree growing to 30 m (98ft) by 12 m (39ft) at a fast rate.
It is hardy to zone 6. It is in flower in April, and the seeds ripen in October. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Insects." [PFAF]

Status: Native. [E-flora]
General: "Large, deciduous, spreading tree up to 30 m tall; branches greenish barked, smooth; older bark greyish-brown, ridged and often covered with lichens and mosses." [IFBC-E-flora] "Western maples are majestic trees that can grow to 65 feet (20 m) tall." [Jones TDFB]
Leaves: "Opposite, 10-30 cm wide, deeply 5-lobed, tips abruptly sharp-pointed, dark green above and paler green below, turning yellow in fall, stalks with milky juice when cut." [IFBC-E-flora] "Bigleaf maple is readily distinguished by the paired (opposite) long-stalked, very large leaves 5-14 in. (12.5-35.5 cm.) long and broad, which are heart-shaped, deeply 5-lobed with additional smaller lobes, and with few teeth." [Viereck ATS]
Flowers: "Inflorescence racemose with male and female flowers on the same plant; numerous on short stalks, appearing with or before the leaves; petals greenish-white," [IFBC-E-flora]
Fruits: "Winged, in pairs, 3-6 cm long, yellowish-brown, hairy, pairs attached in a V-shape." [IFBC-E-flora]
USDA Flower Colour: Yellow
USDA Blooming Period: Mid Spring
USDA Fruit/Seed characteristics:

Colour: Brown
Present from Summer to Fall [USDA-E-flora]

Habitat / Range
"Moist to mesic forests and open slopes in the lowland and montane zones; common in SW BC west of the Coast-Cascade Mountains; S to CA, disjunct in ID." [IFBC-E-flora] "It is extremely flood tolerant and often remains in floodplain habitats.... Bigleaf maple's shade tolerance is low to moderate. It grows most rapidly in small forest openings and open areas". [PPNWNP]

Ecological Indicator Information
"A shade-intolerant, submontane to montane, Western North American deciduous broad­leaved tree distributed more in the Pacific than the Cordilleran region. Occurs in maritime to submaritime cool mesothermal climates on fresh to very moist, nitrogen-rich soils (Moder and Mull humus forms). Its occurrence decreases with increasing elevation, latitude, and continentality. Common in pure or mixed-species stands (usually with red alder or black cottonwood) on alluvial, seepage, and stream-edge sites; occasional on water-shedding sites; dominant in primary succession on fragmental colluvial soils. This fast -growing tree regenerates abundantly from stump sprouts in clearings, thus hindering regeneration and growth of conifers. Its calcium-rich bark supports well developed corticolous moss communities. Characteristic of young-seral forests."[IPBC][E-flora]

Edible Uses

Other Uses

Medicinal Uses


Maple Syrup

"In any event, the quality of the sirup made from the bigleaf maple trees in this study was lower than sirup from the sugar maple, being generally comparable to sirup made from eastern soft maples, such as red and silver maple. The sap from the soft maples, like the bigleaf maple sap, often is low in sugar content. Some of the bigleaf samples did have a trace of an unfamiliar “varnish” taste, but this was not too objectionable. It occurred only in late-season sap collections which may not warrant collection anyway because of low sap flow. With experience in collecting and processing bigleaf maple sap, procedures surely will be found to make a good, marketable sirup, even if its flavor may be different from that of sugar maple." [Ruth et al.,1972]
"Past experience with bigleaf maple in the Pacific Northwest has shown an annual sap flow of 3 to 6 gallons per tree, with about 35 gallons of sap required to make 1 gallon of sirup." [Ruth et al.,1972]
"...trees producing well at the beginning of the sap-flow season continued for that season and tended to be good producers in subsequent seasons." [Ruth et al.,1972]
"Standard practice in the East is that sap must not remain in the buckets or sap bags more than a few hours before it is collected; otherwise it will ferment and spoil (10)." [Ruth et al.,1972]
The sap was brought to boiling quickly; then the heat was reduced to maintain a gentle, steady boiling. Scorching of sirup was at a minimum. The foam formed during the early part of the boiling was skimmed continuously. The finishing point of the sirup was determined with a laboratory refractometer. [Ruth et al.,1972]
Sap started flowing right after tapping on November 17, increased between December 4 and 7, continued to flow intermittently at a somewhat lower level through January 21, then tapered off rapidly in late January in spite of apparently favorable sugar weather.... New tapholes tapped February 8 began to flow immediately and the sap volumes measured for the February 8-11 period were the highest of the season. This was followed by several heavy flows through March 8."
The new trees tapped January 18 produced high sap flows January 18-21 and February l-11 (fig. 4). Flows from all trees tapered off in mid-March and only a trace of sap flowed after March 22. Bud bursting was about March 29."
"Total 1970-71 season sap flow per taphole for trees originally tapped November 17, 1970, ranged from zero to almost 17 gallons". [Ruth et al.,1972]
"Sweetness of bigleaf maple sap varied among individual tapholes from 1.0 to 2.6 degrees Brix.... Average sap sweetness varied during the season with a peak of 1.4 degrees Brix reached about January 25". [Ruth et al.,1972]
"Although the bigleaf maple sirup was very tasteful, all the samples were low in typical sugar maple flavor. This low level of the usual predominant flavor allowed other flavors to be identified. One was a detectable but not too objectionable varnishlike taste in some of the late-season samples.... additional heat... did not improve the flavor. Rather, the Varnish taint” was increased in those late season samples that had it. The color of the Oregon sirup was dark for a product concentrated in steam kettles, and this does not correlate with the low value for invert sugar." [Ruth et al.,1972]


"Of easy cultivation, it prefers a good moist well-drained soil[11] and a position that is at least moderately sunny[11, 200]. Grows well in heavy clay soils. Chlorosis can sometimes develop as a result of iron deficiency when the plants are grown in alkaline soils, but in general maples are not fussy as to soil pH. Growth of young plants is rapid in the wild, slowing down after 40 -50 years with a maximum life span of about 275 years[229]. This species thrives in Britain but it can be cut back in a severe winter if that follows a mild autumn[11]. A very ornamental plant[1]. Most maples are bad companion plants, inhibiting the growth of nearby plants[18, 20]." [PFAF] "...maturity reached at 150 years or more." [Ruth et al.,1972] Regenerates "... vegetatively from stump sprouts or root suckering as well as through seed." [Northcote FF] "It is also a good tree to plant along streambanks to prevent erosion". [PPNWNP]

Cultural Modification:

Species Interactions


"Seed - best sown as soon as it is ripe in a cold frame, it usually germinates in the following spring. Pre-soak stored seed for 24 hours and then stratify for 2 - 4 months at 1 - 8oc. It can be slow to germinate. The seed can be harvested 'green' (when it has fully developed but before it has dried and produced any germination inhibitors) and sown immediately. It should germinate in late winter. If the seed is harvested too soon it will produce very weak plants or no plants at all[80, 113]. When large enough to handle, prick the seedlings out into individual pots and grow them on until they are 20cm or more tall before planting them out in their permanent positions. Layering, which takes about 12 months, is successful with most species in this genus. Cuttings of young shoots in June or July. The cuttings should have 2 - 3 pairs of leaves, plus one pair of buds at the base. Remove a very thin slice of bark at the base of the cutting, rooting is improved if a rooting hormone is used. The rooted cuttings must show new growth during the summer before being potted up otherwise they are unlikely to survive the winter." [PFAF] Soak 48 hours and stratification for 45-130 days, incubation 20OC for 28 days. [Leadem FSSB]

"Seed tends to decay rapidly and cannot be stored for long periods of time. Zasada et al.... Place the seeds in airtight containers soon after collection and store at 1oC until stratification begins. Cold stratify at 1-5oC for 40-80 days prior to sowing. Buis (1996) suggests stratifying over winter in a refrigerator and sowing in February or early March but has also noted excellent germination by sowing directly in the fall. Sow in mulched beds and grow for two years before transplanting or outplanting (Olson and Gabriel 1974, Uchytil 1989, Haeussler at al. 1990)." [PPNWNP]

"Bigleaf maple sprouts vigorously from the root crown after it is top killed or cut (Uchytil 1989). Small seedlings, with about two or three leaves, can be salvaged from construction sites or from under mature trees and transplanted into containers (Buis 1996)." [PPNWNP]


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