Identification key for the species of the genus, based on vegetative features, from specimens in West-European collections. Jan De Langhe, October 2007 - update May 2008 - .html version May 2009.
This key is based on vegetative characteristics, visible during the longest possible period of the year, rarely observation is founded on flower or fruit.
Acer is a large genus, with numerous species. This table assembles only these in general culture and in specialised collections. Major hybrids, infraspecific taxa, and some rare species, are discussed (in lower case) under the parents or respectively related taxon.
To improve accuracy:
- Use a hand lens to judge bud scale scars and hairiness.
- Features like hairiness and presence of milky sap can decrease during Autumn.
- Look at the entire plant.
- Young specimens and strong shoots give a distorted view.
- Beware of hybridisation, especially with plants raised from seed gathered in collections.
4 a Leaflets ≥3, abaxially green or pale green. Shoot at base with 2-3 (4-5) pairs of bud scale scars (terminal bud ≤5 pairs of bud scales). Sectio NEGUNDO. -> 5
4 b Leaflets always 3, abaxially blue-green. Shoot at base with >5 pairs of bud scale scars (terminal bud >5 pairs of bud scales). Sectio TRIFOLIATA. -> 7
5 a Leaflets 3-5 (7-9). IF 3: terminal leaflet and lateral leaflets often different in shape. Petiolule terminal leaflet often ≥3 × longer than that of lateral leaflets. -> A. negundo (Negundo) - Image 2 - Image 3
- Shoot +/- glabrous.
- - Leaflets 3-7 (9), ≥3 cm broad, abaxially glabrous. -> A. negundo subsp. negundo
- - Leaflets 3, ≤3 cm broad, abaxially densely hairy. -> A. negundo subsp. mexicanum
- Shoot hairy.
- - Leaflets 3 (-5?), abaxially glabrous or lightly hairy on midrib. -> A. negundo subsp. interius
- - Leaflets 3-7, ovate, (at first) densely and white hairy. -> A. negundo subsp. californicum
5 b Leaflets always 3. Terminal leaflet and lateral leaflets +/- similar in shape. Petiolule (mature) terminal leaflet rarely 2-3 × longer than that of lateral leaflets. -> 6
6 a Leaf margin ciliate. Leaflets coarsely serrate to dentate. -> A. cissifolium (Negundo/Cissifolia) - Image 2
6 b Leaf margin glabrous. Leaflets entire or with a few small teeth at margin, but on strong shoots and young plants often serrate (dentate). -> A. henryi (Negundo/Cissifolia) - Image 2
7 a Petiole glabrous. Leaflet not undulate at margin, +/- regular serrate, ≥10 teeth per side. Bark smooth. -> A. mandshuricum (Trifoliata/Mandshurica)
7 b Petiole hairy. Leaflet often undulate at margin, irregular coarsely and bluntly toothed to lobed, <8 teeth per side. Bark smooth, fissured or peeling. -> 8
8 a Bark smooth. Leaflet +/- undulate at margin, from top to base, with not too shallowly increasing, <5 mm deep teeth. -> A. maximowiczianum (Trifoliata/Grisea) - Image 2 - Image 3
8 b Bark fissured or peeling. Leaflet, from top to base, with increasing 5-15 mm deep teeth. -> 9
9 a Bark cinnamon coloured, peeling in papery horizontal curls. Bud short and thick. ->A. griseum (Trifoliata/Grisea) - Image 2
- different: bark vertically fissured and/or horizontal peeling, leaf with features between the parents. ->A. griseum × A. maximowiczianum - Image 2 - Image 3
9 b Bark grey-beige, coarse and fibrous, vertically fissured. Bud long and slender. ->A. triflorum (Trifoliata/Grisea) - Image 2
10 a Shoot at base with 2-4 pairs of bud scale scars. Terminal bud elongated and stalked, (closed with 2 pair +/- valvate scales). OR terminal bud on vegetative shoot often reduced and 2 buds on shoot end. -> 11
10 b Shoot at base with ≥4 pairs of bud scale scars. Terminal bud ovoid to long ovoid, not stalked (closed with ≥4 pairs bud scales). -> 38
13 a Terminal bud vegetative shoot rarely reduced, +/- elongated and stalked. Shoot at base with 2-3 pairs of bud scale scars. -> 14
13 b Terminal bud vegetative shoot reduced. Shoot at base with 2-4 pairs of bud scale scars. Sectio PALMATA. -> 77
14 a Shoot at base with 2-3 pairs of bud scale scars. Lamina abaxially without membranous domatia in vein axils. Sometimes vague, +/- green-yellow bark stripes on trunk, branch, shoot. Sectio PARVIFLORA and GLABRA. -> 15
14 b Shoot at base with 2 pairs of bud scale scars. Lamina abaxially with membranous domatia in vein axils (when vein axils are densely hairy, remove the hairs to examine this). Often conspicuous blue-green bark stripes on trunk, branch, shoot. Sectio MACRANTHA. -> 23
15 a Leaf lobed AND terminal lobe broader than long. Lamina average 15-20 cm across. Bark without stripes. -> A. nipponicum (Parviflora/Parviflora) - Image 2
15 b Leaf lobed AND terminal lobe longer than broad. OR leaf unlobed. Lamina smaller. Bark sometimes with light stripes. -> 16
16 a Leaf unlobed, resembling a Tilia leaf, AND cordate at base. Margin +/- regular serrate-dentate at margin. No bark stripes. -> A. distylum (Parviflora/Distyla) - Image 2
16 b Leaf different. -> 17
17 a Bark rough, +/-peeling and/or flaking. Hairiness yellowish to +/- rusty coloured, mainly on bud, top petiole (veins abaxial). -> A. caudatum (Parviflora/Caudata)
- Leaf margin finely serrate. Lobes acuminate, sharply serrate at apex. -> A. caudatum subsp. caudatum - Image 2
- Leaf margin coarsely serrate. Lobes acute to acuminate, entire at apex. -> A. caudatum subsp. ukurunduense - Image 2
17 b Bark smooth or slightly fissured. Hairiness whitish, fading or absent. -> 18
18 a Lamina abaxially pale green to blue-green AND fully glabrous. -> A. glabrum (Glabra/Glabra)
- Leaf mainly simple (deeply lobed leaf and/or compound leaf can be present).
- - Leaf <6 cm across. -> A. glabrum subsp. glabrum
- - Leaf >6 cm across. -> A. glabrum subsp. douglasii - Image 2
- Leaf compound; with 3 leaflets, or almost so. -> A. glabrum subsp. neomexicanum
18 b Lamina abaxially green to grey-green AND at least with hairs in vein axils. -> 19
20 a Lamina 8-17 cm long. Terminal lobe ⅓-½ length lamina, base rarely narrowed. Sinus between lobes sharp, not narrow. -> A. spicatum (Parviflora/Caudata) - Image 2
20 b Lamina <10 cm long. Terminal lobe ½- ⅔ length lamina, base narrowed. Sinus between lobes narrow. -> A. barbinerve (Glabra/Arguta) - Image 2
21 a Leaf unlobed, OR unlobed AND weakly 3-lobed (<2 cm long). -> A. stachyophyllum (Glabra/Arguta) - Image 2
- Multi-stemmed and invasive suckers from base. Lamina often <5 cm. -> A. stachyophyllum subsp. betulifolium
- Multi-stemmed. Lamina often >5 cm. -> A. stachyophyllum subsp. stachyophyllum
21 b Leaf 3- to 5-lobed. Lateral lobes >2 cm long. -> 22
22 a Leaf 3- to 5-lobed, ≤15 cm long, smooth/soft to the touch. Terminal lobe ≥½ length lamina. Lateral lobes caudate. Lamina abaxially hairy in vein-axils. -> A. acuminatum (Glabra/Arguta) - Image 2
22 b Leaf (3-) 5- (7-) lobed, <10 cm long, rough to the touch. Terminal lobe ≤½ length lamina. Lateral lobes acuminate. Lamina abaxially hairy in vein-axils AND on venation. -> A. argutum (Glabra/Arguta)
25 a Unlobed leaf ≥2 × longer than broad AND/OR leaf apex gradually caudate. Lamina never wrinkled or bulged, sometimes (weakly) 3-lobed AND lateral lobes near the base. -> 26
25 b Unlobed leaf <2 × longer than broad AND/OR leaf apex abruptly (+/- long) acuminate. Lamina sometimes wrinkled or bulged, sometimes (weakly) 3- to 5-lobed AND lateral lobes near the middle. -> 28
27 a Leaf apex sharp and deeply serrate, +/- caudate, with pointed tip. -> A. caudatifolium (Macrantha)
27 b Leaf apex shallowly serrate, acuminate to caudate, with rounded tip. -> A. crataegifolium (Macrantha) - Image 2
28 a Domatia obvious, ALSO in axils between lateral veins and veinlets (LENS!)
- Lamina (mostly) <15 cm long, +/- flat to +/- wavy, never faint or wrinkled. Very variable species (lamina unlobed to shallowly lobed, margin sharp to bluntly toothed, lamina 1,5 to 2 × as long as broad). -> A. davidii (Macrantha) - Image 2 - Image 3
- - Lamina >7 cm long, unlobed to weakly 3-lobed. -> A. davidii subsp. davidii
- - Lamina <7 cm lang, shallowly 3- to 5-lobed (unlobed on old and weak shoot). -> A. davidii subsp. grosseri
- Lamina 10-30 cm long, often curved or bulged and faint or wrinkled. Hybrid between A. davidii and A. pensylvanicum. -> A. × conspicuum - Image 2 - Image 3 - Image 4
28 b Domatia only in axils between midrib and lateral veins. Margin sharply serrate. Leaf apex caudate. -> A. morifolium (Macrantha) - Image 2
29 a Sinus between terminal and lateral lobe very narrow and deep, by which the lobes almost touch at base or often partly overlap. -> 30
29 b Sinus between terminal and lateral lobe broad, with a lot of space between the lobes. -> 31
30 a Terminal lobe and lateral lobes gradually caudate. Fruits >10, in narrow long pendulous racemes. Autumn colour +/- red. Lamina abaxially with short dark brown hairs in basal and +/- in other vein axils. -> A. micranthum (Macrantha) - Image 2
30 b Terminal lobe and lateral lobes rather abruptly acuminate. Fruits <10, initially in erect racemes. Autumn colour often yellowish. Lamina abaxially with long rusty hairs in basal vein axils, +/- on venation and petiole. -> A. tschonoskii (Macrantha) - Image 2
- Lobes acuminate. Petiole and shoots not or vaguely red. -> A. tschonoskii subsp. tschonoskii
- Lobes acuminate to +/- caudate. Shoot and petiole red tinged to conspicuous red (synonym: A. komarovii, A. tschonoskii var. australe, A. tschonoskii var. rubripes). -> A. tschonoskii subsp. koreanum
32 a Lamina abaxially with rusty coloured hairs on venation and vein axils (fading feature). -> A. rufinerve (Macrantha) - Image 2
32 b Lamina abaxially different. -> A. tegmentosum (Macrantha) - Image 2
33 a Lamina >12-15 cm long, often up to 25 cm long and 10-20 cm broad. -> A. pensylvanicum (Macrantha) - Image 2
- Different: Lamina often curved or bulged and faint or wrinkled. Lateral lobes sometimes weakly developed or absent. Hybrid between A. davidii and A. pensylvanicum. -> A. × conspicuum - Image 2 - Image 3 - Image 4
33 b Lamina <12-15 cm long. -> 34
34 a Terminal lobe longer than broad AND the reverse on the same tree (often on the same shoot). Leaf margin with an average of <7 teeth/cm. -> 35
34 b Terminal lobe obvious longer than broad. Leaf margin with ≥7 teeth/cm average (! Some taxa with coarser incisions, but then with terminal lobe always longer than broad). -> 36
35 a Leaf 5-lobed, basal lobes mostly <5 mm. Midvein with 2 pairs of basal veins AND ≥7 pairs of lateral veins. Leaf margin irregular, fine and +/- double serrate. -> A. capillipes (Macrantha) - Image 2
35 b Leaf 5-lobed, basal lobes mostly >5 mm. Midvein with 2 pairs of basal veins AND 4-6 (rarely 8) pairs of lateral veins. Leaf margin irregular, coarsely serrate. -> A. rubescens (Macrantha) - Image 2
36 a Lamina average ≤7 cm long, mostly with 2 small lateral lobes 1-2 cm long, sometimes a few leaves unlobed. -> A. davidii subsp. grosseri (Macrantha)
36 b Lamina average >7 cm long, AND/OR lateral lobes more obvious, longer. -> 37
37 a Lamina +/- as broad as long and abaxially particular glabrous in vein axils. Taxon with doubtful status, features between A. davidii and A. pectinatum. -> A. metcalfii (Macrantha) - Image 2
37 b Lamina +/- as broad as long AND abaxially hairy in vein axils. OR lamina longer than broad. Very variable. -> A. pectinatum (Macrantha) - Image 2
- Lamina +/- as long as broad,
- - 3- to 5-lobed. Terminal lobe ≤½ lamina length, lateral lobes ovate-triangular and caudate. Margin fine and sharply serrate with +/- 1 teeth per mm. -> A. pectinatum subsp. pectinatum - Image 2
- - (3-) 5-lobed. Terminal lobe ≥½ lamina length, lateral lobes triangular and gradually acuminate. Leaf margin +/- irregular and coarsely serrate. -> A. pectinatum subsp. maximowiczii - Image 2
- Lamina longer than broad,
- - (unlobed-) 3-lobed. Lateral lobes (very) small <2 cm long (base below the middle). -> A. pectinatum subsp. laxiflorum - Image 2
- - 3- to weakly 5-lobed. Lateral lobes >2 cm long.
- - - Terminal lobe ≥½ lamina length. Lateral sinus below the middle of lamina. Leaf margin double serrate. -> A. pectinatum subsp. forrestii - Image 2
- - - Terminal lobe ⅓-½ lamina length. Lateral sinus often above the middle of lamina. Leaf margin very finely and sharply serrate with +/- 1 teeth per mm. -> A. pectinatum subsp. taronense - Image 2
40 a Shoot greenish and staying so, not woody the second (and following) growing season, eventually with red or brown, sometimes with bluish ripe or stripes. -> 41
40 b Shoot becoming grey- to brownish woody, at least so the second growing season. -> 42
41 a Leaf unlobed and weakly 3-lobed, OR 3- to 5-lobed. Lamina rigid, firm and net-veined. Leaf base cordate. -> A. amplum (Platanoidea)
- Leaf (3-) 5-lobed.
- - Terminal lobe often (much) broader than long, often 'broad shouldered lamina'. -> A. amplum subsp. amplum - Image 2
- - Terminal lobe often >½ lamina length (synonym A. chapaense). -> A. amplum subsp. bodinieri - Image 2
- Leaf unlobed to 3-lobed.
- - Leaf 3- lobed, sinus between lobes +/- sharp, lobes directed sideward. -> A. amplum subsp. tientaiense
- - Leaf unlobed to weakly 3- lobed, resembling Catalpa. -> A. amplum subsp. catalpifolium
41 b Leaf 5- to 7-lobed (3-lobed leaf possible but then lamina <7 cm long). Lamina thin, papery, not net-veined. Leaf base truncate to +/- cordate. -> A. cappadocicum (Platanoidea) - Image 2
- Tree with smooth bark. Leaf 5- to 7-lobed.
- - Crown round and broad. Shoot green, sometimes lightly bloomed. Leaf 5- to 7-lobed. Hairiness lamina abaxially mainly restricted to basal vein axils. -> A. cappadocicum subsp. cappadocicum - Image 2
- - Crown distinctive columnar. Shoot distinctive bloomed. Leaf mainly 5-lobed (small leaf sometimes 3-lobed), margin more undulated. Hairiness lamina abaxially often in all vein axils. -> A. cappadocicum subsp. lobelii - Image 2 - Image 3 - Image 4
- Small tree, bark often ridged. Leaf 5-lobed.
- - Lamina <10 cm across. Lobes narrow and deep, especially long acuminate. -> A. cappadocicum subsp. sinicum
- - Lamina ≤7 cm across. Lobes short, +/- blunt to acuminate (lamina sometimes firm textured, various forms cultivated) Shoot quickly reddish brown. Small tree with entangled branches. -> A. cappadocicum subsp. divergens
Different, some hybrids with 5-lobed to weakly 7-lobed leaf with terminal lobe entire as well as slightly toothed:
- Terminal lobe entire as well as with blunt and rounded teeth. Features between A. campestre and A. cappadocicum. -> A. × zoeschense - Image 2
- Terminal lobe entire as well as with rounded and pointed teeth.
- - Present teeth rounded to pointed at tip. Leaf margin undulate and initially ciliate. Lamina abaxially and petiole less hairy compared with A. miyabei (especially obvious on young leaves). Features between A. cappadocicum and A. miyabei. -> A. × hillieri - Image 2
- - Present teeth pointed and sometimes bristly at tip. Features between A. cappadocicum and A. platanoides. A. × verhaegheanum. Geerinck: in Nat. Belg., 78(1): 9 (1997). Similar hybrid in Hillier Gardens between A. cappadocicum subsp. sinicum and A. platanoides. -> A. × verhaegheanum - Image 2
42 a Lamina abaxially hairy. Leaf 3- to 5-lobed. -> A. longipes (Platanoidea) - Image 2
42 b Lamina abaxially glabrous, except venation and/or vein axils. Sometimes lamina abaxially densely hairy but than leaf >5-lobed. -> 43
43 a Leaf 3-, or weakly 5- lobed, rarely unlobed, small: +/- ≤6 × 6 cm. -> A. tenellum (Platanoidea)
43 b Leaf 5- to 7- (9) lobed, >6 × 6 cm. Very variable species, numerous subspecies with only a few cultivated. -> A. pictum (Platanoidea) - Image 2
- Lamina abaxially fully hairy. Leaf 5-7 lobed. -> A. pictum subsp. pictum - Image 2
- Lamina abaxially glabrous or hairy only on midrib and lateral veins.
- - Leaf 5- to 7-lobed. -> A. pictum subsp. mono
- - Leaf 7- to 9-lobed. -> A. pictum subsp. okamotoanum - Image 2
Image, not in key: Acer pictum × Acer platanoides - Image 2
44 a Teeth with bristly enlargement present. Petiole and leaf margin glabrous. -> 45
44 b Teeth pointed or rounded, without bristly enlargement. Petiole often hairy, leaf margin ciliate (fading in Autumn and on mature leaf). -> 46
45 a Terminal lobe >½ lamina length, entire OR with ≤2 +/- teeth (rarely more small teeth); abaxially with weak lateral veins and glabrous vein axils. -> A. truncatum (Platanoidea) - Image 2
45 b Terminal lobe <½ lamina length, always toothed, often with more, (sinuous) teeth; abaxially with obvious lateral veins and hairy vein axils. -> A. platanoides (Platanoidea) - Image 2
- Large tree.
- - Leaf +/- uniform. Lobes obviously toothed, often more teeth per side. Lamina abaxially hairy in vein axils. -> A. platanoides subsp. platanoides
- - Leaf very variable in shape, sometimes on the same shoot: Some hybrids (see also 41b):
- - - Leaves like A. platanoides as well as (smaller) leaves like A. truncatum with lobes less (bristly) toothed. Features between both parents. -> A. platanoides × A. truncatum - Image 2
- - - Teeth pointed and/or bristly. Features between A. cappadocicum and A. platanoides. -> A. × verhaegheanum - Image 2
- - - Lobes sometimes absent, supposed hybrid between A. cappadocicum subsp. lobelii and A. platanoides (sometimes regarded as a form of the latter). -> A. × dieckii
- Shrub or small tree. Lobes less toothed. Lamina abaxially hairy. -> A. platanoides subsp. turkestanicum
48 a Lamina average ≥10 cm long. Terminal lobe mostly long acuminate, margin mainly with 1-2 teeth. Hairiness more obvious: often as well on lamina adaxially as abaxially, especially on venation and petiole. -> A. miyabei (Platanoidea)
- Leaf with 3 lobes. Terminal lobe acuminate, lateral lobe rather +/- obtuse. -> A. miyabei subsp. miaotaiense - Image 2
- Leaf with 5 lobes. Terminal and lateral lobes acuminate.
- - Margin with rounded teeth. Lamina abaxially and petiole obviously hairy. -> A. miyabei subsp. miyabei - Image 2
- - Margin with pointed to rounded teeth. Lamina abaxially and petiole less hairy (especially obvious on young leaves). Features between A. miyabei and A. cappadocicum -> A. × hillieri - Image 2
48 b Lamina average ≤10 cm long. Terminal lobe often shorter and +/- blunt at apex, leaf margin mostly entire or with one teeth. Hairiness less obvious: more restricted to venation (mainly less obvious on lamina adaxially and petiole or lacking there). See also hybrids. -> A. campestre (Platanoidea) - Image 2
Different, some hybrids:
- Leaf 5- (to weakly 7-) lobed. Terminal lobe narrowing towards base. Lateral lobes long, with 1-2 shallow rounded teeth. Features between A. campestre and A. cappadocicum. -> A. × zoeschense - Image 2
- Leaf 3- (to weakly 5-) lobed. Terminal lobe broadest at base. Lateral lobes short, +/- long pointed at apex, entire or almost so. Features between A. campestre? and A. monspessulanum. -> A. × bornmuelleri (Acer/Monspessulana) - Image 2
49 a Terminal lobe not V-shaped, broadest at base, with 1 (or 2) small pointed teeth per side, AND lateral lobes entire or almost so. -> A. sinopurpurascens (Lithocarpa/Lithocarpa) - Image 2
49 b Terminal lobe V-shaped, narrow at base and broader above the middle. Terminal lobe AND lateral lobe with more and obvious teeth. -> A. diabolicum (Lithocarpa/Lithocarpa) - Image 2 - Image 3
50 a Bud, shoot and fruit stiff-hairy (fading in Autumn). -> A. sterculiaceum (Lithocarpa/Lithocarpa) - Image 2 - Image 3
- Leaf 3-lobed, remarkable thick, >15 cm across. Lateral lobes often small. Leaf margin coarsely toothed to entire. -> A. sterculiaceum subsp. thomsonii - Image 2
- Leaf 3- to more-lobed, stout to thick. Lateral lobes obvious.
- - Leaf 3- (weakly 5-) lobed, <15 cm across. Leaf margin irregular, distantly and coarsely dentate. Fruits a few in short infructescence. -> A. sterculiaceum subsp. franchetii - Image 2
- - Leaf 3-5 (7) lobed, >15 cm across. Leaf margin more regular toothed. Fruits: numerous in long infructescence. -> A. sterculiaceum subsp. sterculiaceum - Image 2
50 b Bud AND shoot AND fruit never stiff- hairy at the same time. -> 51
52 a Lamina leathery AND fully wintergreen AND with pointed apex AND unlobed or both unlobed and 3-lobed. Sectio PENTAPHYLLA, HYPTIOCARPA. -> 53
52 b Lamina different. Sectio ACER, GINNALA, PUBESCENTIA, RUBRA, (PENTAPHYLLA). -> 56
54 a Lamina <10 cm long, ovate to oblong ovate <2 × longer than broad. Juvenile leaf 3-lobed (Leaf margin shallowly toothed at first, entire later). -> A. paxii (Pentaphylla/Trifida) - Image 2
54 b Lamina >10 cm long, oblong ovate 2 × longer than broad. Leaf rarely 3-lobed. -> 55
55 a Lamina adaxially with obvious visible venation, lateral veins >6 pairs. Lamina up to +/- 15 × 5 cm, apex +/- pointed at tip (varieties with smaller leaf, or lamina abaxially green in place of blue-green are sometimes recognised). -> A. oblongum (Pentaphylla/Trifida) - Image 2
55 b Lamina adaxially with less obvious venation, lateral veins ≤6 pairs. Lamina longer and especially broader, up to +/- 18 × 8 cm, apex +/- rounded at tip. -> A. laurinum (Hyptiocarpa) - Image 2
56 a Leaf deeply 3-lobed: terminal lobe finger-shaped (narrow and deep) AND ≥¾ lamina length, (much) longer than lateral lobes (on strong shoots lobes more equal in size). -> Sectio PUBESCENTIA. -> A. pilosum (Pubescentia) - Image 2
56 b Leaf different (terminal lobe never finger-shaped slender and narrow). Sectio, GINNALA and (ACER, PENTAPHYLLA, RUBRA). -> 57
59 a Leaf apex mostly acute to acuminate, OR IF always acute, then lateral lobes absent or with apex +/- below the middle of lamina. -> 60
59 b Leaf apex mostly rounded to obtuse, OR IF acute, then lateral lobes with apex very obvious above the middle of lamina. -> 63
61 a Lamina abaxially blue-green, very contrasting with the adaxially green colour. Sectio (RUBRA). -> A. pycnanthum (Rubra) - Image 2
61 b Lamina abaxially green, little or not contrasting with adaxially colour. Sectio GINNALA. -> A. tataricum (Ginnala)
- Lamina <4 cm long. -> A. tataricum subsp. semenovii
- Lamina >7 cm long.
- - Leaf unlobed, or with shallow lobes <1 cm deep, also eventually lobed towards apex. -> A. tataricum subsp. tataricum
- - Leaf lobed at base.
- - - Lobes blunt at apex. Leaf margin +/- bluntly serrate. -> A. tataricum subsp. aidzuense - Image 2
- - - Lobes acute to acuminate at apex. Leaf margin sharply serrate. -> A. tataricum subsp. ginnala - Image 2
62 a Lamina at margin partly entire and shallowly (+/- appressed) serrate, abaxially often pale green to blue-green. Sectio (PENTAPHYLLA). -> A. buergerianum (Pentaphylla/Trifida) - Image 2 - Image 3 - Image 4
- Leaf mainly 3-lobed.
- - Lobes directed forward, lamina abaxially pale blue-green. -> A. buergerianum subsp. buergerianum
- - Lobes directed sideward, lamina abaxially remarkable blue-green. -> A. buergerianum subsp. ningpoense - Image 2
- Leaf unlobed to (weakly) 3-lobed. -> A. buergerianum subsp. formosanum
62 b Lamina fully entire at margin, rarely with a blunt-rounded little teeth. Similar but totally unrelated hybrid, features between presumed parents: A. monspessulanum and A. campestre? -> A. × bornmuelleri (Acer/Monspessulana) - Image 2
64 a Leaf semi-wintergreen. Lamina <4 cm, entire at margin (rarely with some shallow little teeth). -> A. sempervirens (Acer/Monspessulana)
64 b Leaf wintergreen. Lamina ≤6 cm (juvenile >), shallowly toothed at margin (sharply on juvenile, becoming entire on adult). -> A. obtusifolium (Acer/Monspessulana) - Image 2
65 a Lateral lobes with apex +/- in or below (never obvious above) the middle of lamia. Terminal lobe longer than broad, rounded to obtuse at apex. -> A. monspessulanum (Acer/Monspessulana) - Image 2
- Tree or small tree. Samara's green.
- - Lamina average <7 cm, abaxially +/- glabrous, only hairy at base. -> A. monspessulanum subsp. monspessulanum
- - Lamina average >7 cm, abaxially densely hairy. -> A. monspessulanum subsp. ibericum
- Dense shrub. Samara's red. Lamina abaxially +/- with rust-coloured hairs. A. monspessulanum subsp. turcomanicum
Different: Shrub to small tree, lamina larger than A. monspessulanum, colour grey-green to yellow-green, Lobes often with more (shallow) teeth. -> A. pentapomicum (Pubescentia) - Image 2
65 b Lateral lobes with apex VERY obvious above the middle of lamia.Terminal lobe broader than long, rounded to obtuse (sometimes terminal lobe longer than broad and then apex acute). Similar hybrids, leaf mainly 3-lobed, sometimes some weakly 5-lobed.
- Lamina remarkable thick and strong, Features between A. monspessulanum and A. opalus.?
- - Lobes short and more rounded. -> A. × coriaceum (Acer/Monspessulana)
- - Lobes longer and more pointed. -> A. × durettii (Acer/Monspessulana)
- Lamina not so remarkable thick and strong, extremely similar hybrids, parents presumed.
- - Features between A. opalus and A. pseudoplatanus? -> A. × hybridum - Image 2
- - Features between A. monspessulanum and A. opalus subsp. obtusatum? -> A. × rotundilobum
67 a Mature lamina conspicuously ciliate at margin and abaxially densely hairy even on the smallest veinlets (See 69a). -> A. saccharum subsp. grandidentatum - Image 2
67 b Mature lamina not ciliate at margin, abaxially glabrous to slightly hairy. -> A. hyrcanum (Acer/Monspessulana)
- Shrub, leaf 3-lobed. Lamina 0,5-1,5 cm across. Leaf margin wavy, with sharp, fine +/- prickling teeth. -> A. hyrcanum subsp. reginae-amaliae
- Tree or shrub, leaf 3- to 5-lobed. Lamina 3-10 cm across. Leaf margin flat, never so finely toothed.
- - Leaf 3-lobed (at most with very small basal lobes, samara's ≤1 cm). A. hyrcanum subsp. sphaerocarpum
- - Leaf 5- lobed (samara's 3-4 cm).
- - - Leaf margin with rounded teeth, or +/- crenate.
- - - - Lamina dull, thin. Terminal lobe with <4 rounded teeth. -> A. hyrcanum subsp. keckianum
- - - - Lamina smooth, thick. Terminal lobe with >5 rounded teeth. -> A. hyrcanum var. granatense
- - - Leaf margin with blunt to +/- sharp teeth.
- - - - Lamina abaxially blue-green. -> A. hyrcanum subsp. intermedium
- - - - Lamina abaxially green.
- - - - - Lobes with acute apex and teeth. -> A. hyrcanum subsp. tauricolum
- - - - - Lobes with blunt apex and teeth. -> A. hyrcanum subsp. hyrcanum
68 a Terminal lobe broad AND with 1-2 (3) +/- sinuous teeth per side. -> A. saccharum (Acer/Saccharodendron) - Image 2
Extremely variable species, following infraspecific taxa are, among others, recognised:
- Lamina >10 cm long. Lobes obvious long acuminate, slender and pointed at apex.
- - Lamina abaxially yellow-green to green, hairiness stiff. Petiole with stipules at base. -> A. saccharum subsp. nigrum - Image 2 - Image 3
- - Lamina abaxially pale green to blue-green, hairiness different. Petiole without persistent stipules.
- - - Lamina abaxially +/- glabrous to softly hairy. Petiole glabrous and slender. -> A. saccharum subsp. saccharum
- - - Lamina abaxially remarkable densely hairy. Petiole densely hairy and rather thick. -> A. saccharum subsp. skutchii - Image 2
- Lamina average <10 cm long. Lobes blunt to pointed or +/- acuminate at apex.
- - Lamina abaxially green to yellow-green. Lobes +/- acuminate. -> A. saccharum subsp. leucoderme
- - Lamina abaxially pale green to blue-green. Lobes blunt to +/- sharp at apex.
- - - Teeth blunt. Terminal lobe hardly narrowing towards base. A. saccharum subsp. floridanum
- - - Teeth rounded. Terminal lobe very narrow towards base. -> A. saccharum subsp. grandidentatum - Image 2
68 b Terminal lobe different (with more teeth per side or remarkable finger-shaped). -> 69
69 a Terminal lobe triangular, broadest at base AND lobes with conspicuous long acuminate apex. A. caesium (Acer/Acer)
- Shoot initially slightly bloomed. Leaf 3- to 5-lobed. -> A. caesium subsp. caesium - Image 2
- Shoot strong bluish-white bloomed (often persistent the 2th year). Leaf (3-) 5- to 7-lobed. -> A. caesium subsp. giraldii - Image 2
69 b Terminal lobe different (if broadest at base than apex not long acuminate). -> 70
70 a Terminal lobe mostly broader than long AND broadest at base, sinus often broad. Leaf margin +/- shallowly (not sharply) toothed. Lamina often bulged or with wrinkled surface, tending to crack when flattened. See also hybrids. -> A. opalus (Acer/Monspessulana)
- Lamina ≥12 cm broad, +/- thick and leathery. Lobes blunt and rounded. A. opalus subsp. obtusatum - Image 2
- Lamina <10 cm broad, thinner. Lobes more pointed. -> A. opalus subsp. opalus
Different: some similar hybrids with often 3-lobed leaf, but weakly 5-lobed leaf can be present.
- Lamina remarkable thick and strong. Features between A. monspessulanum and A. opalus?
- - Lobes short and more rounded. -> A. × coriaceum (Acer/Monspessulana)
- - Lobes longer, more pointed. -> A. × durettii (Acer/Monspessulana)
- Lamina not so thick and strong, very similar hybrids, parents disputable.
- - A. opalus × A. pseudoplatanus? -> A. × hybridum (Acer/Monspessulana) - Image 2
- - A. monspessulanum × A. opalus subsp. obtusatum? -> A. × rotundilobum (Acer/Monspessulana)
70 b Terminal lobe different, longer, AND/OR teeth sharper. -> 71
71 a Terminal bud green, AND well developed >5 mm, AND lateral buds small. -> A. pseudoplatanus (Acer/Acer) - Image 2 - Image 3 - Image 4
71 b Terminal bud different (eventually partly green), AND/OR lateral buds obvious larger. -> 72
72 a Lamina remarkably large, 15-30 cm across. Terminal lobe with ≥5 blunt to rounded, often very robust teeth per side. -> A. velutinum (Acer/Acer) - Image 2
- Crown broad to broad dome-shaped. Samaras forming an angle of +/- 90°.
- - Lamina abaxially green to grey-green, +/- glabrous to densely and pale to rusty-coloured hairy. -> A. velutinum var. velutinum
- - Lamina abaxially blue-green, completaly glabrous. A. velutinum f. glabrescens
- Crown columnar. Lamina abaxially +/- blue-green, hairiness restricted to venation. Samara's forming an angle of >90°. -> A. velutinum var. vanvolxemii - Image 2 - Image 3
Different: Plant with features between the parents, hybrid between A. pseudoplatanus and A. velutinum.
72 b Lamina smaller (IF large, then terminal lobe conspicuous V-shaped and/or with sharper teeth). -> 73
73 a Terminal lobe +/- V-shaped AND with <6 teeth per side. A. heldreichii (Acer/Acer)
- Lobes narrow and very deep. Teeth blunt to rounded. -> A. heldreichii subsp. heldreichiii - Image 3
- Lobes broad and deep. Teeth blunt to pointed. -> A. heldreichii subsp. trautvetteri - Image 2
Different: Leaf with features between A. pseudoplatanus and A. heldreichii. -> A. × pseudoheldreichii
73 b Terminal lobe different (IF V-shaped then teeth more numerous and sharp). -> 74
74 a Leaf 5-lobed, terminal lobe conspicuous narrowed at base, basal lobes obvious. Leaf margin with sharply pointed teeth. -> A. saccharinum (Rubra) - Image 2
Different: Terminal lobe variable narrow to broad at base and leaf margin with +/- blunt teeth, intermediar between the parents A. rubrum and A. saccharinum. -> A. × freemannii (Rubra) - Image 2
74 b Leaf 3- to 5-lobed, terminal lobe not narrowed at base, basal lobes less obvious or lacking. Leaf margin with +/- blunt pointed teeth. -> A. rubrum (Rubra) - Image 2
75 a Leaf base round to +/- cordate. Basal lateral veins ending high in the leaf margin: between ⅓ and ½ lamina length. Lamina abaxially +/- paler green to blue-green than abaxial surface. -> A. cordatum (Palmata/Penninervia)
75 b Leaf base cuneate to rounded. Basal lateral veins ending low in the leaf margin: under ⅓ lamina length. Lamina abaxially and adaxially +/- concolorous, green. -> 76
76 a Lamina >10 cm long. Venation reticulate (both surfaces). Leaf margin +/- undulate. -> A. laevigatum (Palmata/Penninervia) - Image 2
76 b Lamina <10 cm long. Venation not reticulate. Leaf margin +/- flat. -> A. fabri (Palmata/Penninervia)
79 a Leaf 3-lobed, ≤10 cm long. Lobes slender and finger-shaped, with finely serrated margin. Terminal lobe >⅘ lamina length. Petiole 3-5 cm, long + thin compared with lamina length.
- Lobes apical conspicuous >2 cm long, line-caudate. Lamina abaxially rusty-hairy in vein axils. -> A. wardii (Wardiana)
- Lobes apical not as long caudate. Lamina abaxially glabrous. -> A. tutcheri (Palmata/Sinensia)
79 b Leaf 3-lobed (rarely unlobed, or 5-lobed and juvenile), 10-25 cm long. Lobes and margin different. Petiole 2-4 cm, short and thick compared with lamina length.
- Leaf unlobed to 3-lobed, 10-25 cm. Terminal lobe caudate and lateral lobes acute to +/- caudate at apex. Leaf margin initially coarsely serrate, entire later. -> A. calcaratum (Palmata/Sinensia) - Image 2
- Leaf 3-lobed (juvenile 5-lobed), 10-15 cm long. Lobes bluntly pointed to long acuminate. Leaf margin coarsly dentate, entire later (several subspecies are recognised). -> A. tonkinense (Palmata/Sinensia)
81 a Leaf 3- to 5-lobed, basal lobes very small, <1 cm. Lobes oblong to broad ovate, entire to +/- fine-sharply serrated towards apex. Leaf base cuneate to +/- rounded. -> A. campbellii subsp. wilsonii (Palmata/Sinensia) - Image 2
81 b Leaf 5-lobed, basal lobes >1 cm (sometimes 3- and/or 4-lobed leaf present). Lobes (elongate) triangular, gradually tapered, fully serrate at margin. Leaf base truncate to weakly cordate. -> 82
82 a Terminal lobe ⅔ to ¾ lamina length. -> A. oliverianum (Palmata/Sinensia)
- Lamina abaxially hairy in vein axils and +/- along veins. -> A. oliverianum subsp. oliverianum - Image 2
- Lamina abaxially glabrous, often with purplish hue (A. serrulatum in FOC). -> A. oliverianum subsp. formosanum - Image 2
82 b Terminal lobe ½ lamina length.
- Petiole felt-like hairy. Lamina not leathery, abaxially green (A. pubinerve in FOC). -> A. wuyuanense (Palmata/Sinensia)
- Petiole glabrous.
- - Lamina +/- thick, often +/- leathery and smooth waxy to the touch. Leaf base cordate to deeply cordate (A. sinense in FOC). -> A. campbellii subsp. sinense (Palmata/Sinensia) - Image 2 - Image 3 - Image 4
- - Lamina not so thick nor leathery. Leaf base truncate to weakly cordate (looks like a large-leaved A. oliverianum and synonymous in FOC). -> A. schneiderianum (Palmata/Sinensia)
83 a Emerging leaf often remarkable reddish-brown, AND lobes finger-shaped >¾ lamina length, margin coarsely dentate. Mature leaf on older plant is less deeply lobed and less coarsely dentate to very finely serrate (lobes 5, 5-7 sometimes 7-9). (Sectio PALMATA/Sinensia). -> 84
83 b Emerging leaf not so remarkable reddish-brown, not deeper finger-shape-lobed and not more coarsely dentate than mature leaf, but similar and only smaller (lobes 5-7 or more). (Sectio PALMATA/Palmata) -> 85
84 a Leaf variable 5- to 7-lobed (sometimes weakly 9-lobed). -> A. campbellii (Palmata/Sinensia) - Image 2
- Lobes narrow to broad and leaf margin very finely serrate. -> A. campbellii subsp. campbellii
- Lobes narrow and leaf margin irregular sharply serrate (A. flabellatum in FOC). -> A. campbellii subsp. flabellatum - Image 2
84 b Leaf 5-lobed.
- Lamina +/- leathery, abaxially pale green to blue-green. Petiole stout. (A. sinense in FOC, forms with large leaf and long lobes as well as with smaller leaf and short lobes). -> A. campbelli subsp. sinense - Image 2 - Image 3 - Image 4
- Lamina not leathery. Lamina abaxially green. Petiole slender. -> A. elegantulum (Palmata/Sinensia)
86 a Petiole AND annual shoot lasting and densely covered with adpressed, short and stiff hairs. Lamina abaxially initially +/- greyish by similar kind of hairs. Leaf 5- to 7-lobed, resembling a dull-green coloured A. palmatum. -> A. pubipalmatum (Palmata/Palmata)
86 b Petiole AND shoot not so densely nor lasting hairy. Lamina abaxially different IF leaf is 5- to 7-lobed. OR leaf 7- to more-lobed. -> 87
87 a Leaf with 5-7 (sometimes 9-) lobes, long and slender +/- caudate (hybrids between the infraspecific taxa and with other related taxa like A. shirasawanum, A. sieboldianum and A. pseudosieboldianum occur!). -> A. palmatum (Palmata/Palmata)
- Leaf margin finely serrate. Terminal lobe ½- ⅓ lamina length. -> A. palmatum subsp. amoenum - Image 2
- Leaf margin coarsely serrate. Terminal lobe >⅔-¾ lamina length.
- - Lobes 5-7, terminal lobe ⅔-¾ lamina length. -> A. palmatum subsp. palmatum - Image 2
- - Lobes 7 (-9), terminal lobe >¾ lamina length. -> A. palmatum subsp. matsumurae
87 b Leaf with (7) 9-11 (13) lobes, gradually tapered to a point, not caudate. -> 88
88 a Leaf base +/- truncate to somewhat cordate. -> A. tenuifolium (Palmata/Palmata) - Image 2
88 b Leaf base deeply cordate. -> A. pseudosieboldianum (Palmata/Palmata) - Image 2
- Lobes 9-11. -> A. pseudosieboldianum subsp. pseudosieboldianum
- Lobes 9-13. -> A. pseudosieboldianum subsp. takesimense
89 a Lobes 5-7 (rarely 5-9). Leaf margin sharply double serrate with teeth up to 1 mm. -> A. duplicatoserratum (Palmata/Palmata)
89 b Lobes 7-11 (13) (no leaf with 5 lobes present). Leaf margin not so finely serrate. -> 90
92 a Lobes 7-9. Shoot greenish and lasting so the 2nd and 3th year. -> A. circinatum (Palmata/Palmata) - Image 2
92 b Lobes 9-11 (13). Shoot initially green, becoming grey to brown the 2nd year. -> 93
93 a Lobes 9-11. Lamina abaxially +/- dull. Petiole thick and often <½ lamina length (hybrids occur frequently, among others with A. circinatum and A. pseudosieboldianum). -> A. japonicum (Palmata/Palmata) - Image 2
93 b Lobes 9-13. Lamina abaxially shiny. Petiole thin and >½ lamina length. -> A. shirasawanum (Palmata/Palmata) - Image 2 - Image 3
Features based on:
- JDL herbarium specimens.
- living specimens, in various arboreta, botanic gardens and collections.
- Bean, W.J. (1981) Trees and Shrubs hardy in the British Isles I, p.185-240.
- Bean, W.J. (1988) Trees and Shrubs hardy in the British Isles Supplement, p.36-62.
- de Jong, P.C. (1989) European Garden Flora V, p.131-153.
- Fang, W. (1939) A Monograph of Chinese Aceraceae, 346p.
- Gregory, P. (1991-2007) The Maple Society Newsletter.
- Hillier, J. & Coombes, A. (2002)The Hillier Manual of Trees & Shrubs, p.11-20.
- Krüssmann, G. (1978) Handbuch der Laubgehölze I, p.66-114.
- Kurata. (1964) Illustrated Important Forest Trees Of Japan, vol I, p.164-169.
- Kurata. (1968) Illustrated Important Forest Trees Of Japan, vol II, p.90-111.
- Kurata. (1971) Illustrated Important Forest Trees Of Japan, vol III, p.82-95.
- Kurata. (1973) Illustrated Important Forest Trees Of Japan, vol IV, p.44-51.
- Kurata. (1971) Illustrated Important Forest Trees Of Japan, vol V, p.30-33.
- Lee, S. (1963) Forest Botany of China Supplement, p.196-224.
- Le Hardÿ de Beaulieu. (2003) An illustrated Guide to Maples, 464 p.
- Li Hui-Lin. (1963) Woody Flora of Taiwan, p. 485-491.
- Masayoshi, Y (2003) Book for Maples, 400 p.
- More, D. & White, J. (2003) Trees of Britain & Northern Europe, p.608-661.
- Rehder A. (1940) Manual of cultivated trees and shrubs hardy in North America, p.566-586.
- Sargent, C.S. (1921) Manual of the trees of North America, p.681-702.
- Schneider, C.K. (1912) Illustriertes Handbuch der Laubholzkunde II, p. 192-245.
- van Gelderen, C.J. & DM. (1999) Maples for Gardens, 294 p.
- van Gelderen, D.M., de Jong, P.C. & Oterdoom, H.J. (1994) Maples of the World, 458 p.
- Vertrees. (1978) Japanese maples, 189 p.
- Wiegrefe S., Angus H., Gregory P. & Otis D. (2002) International Maple Symposium 2002, 88p.
- Xu T., Chen, Y., de Jong P.C., Otterdoom H.J. & Chang C.-S. (2008) – Aceraceae. In Flora of China Vol. 11., p. 517-553.
I am particularly grateful to Hugh Angus, Piotr Banaszczak, Mona Bourell, Koen Camelbeke, Allen Coombes, Herlinde De Jaeck, Philippe de Spoelberch, Paul Goetghebeur, Peter Gregory, Andy Marsh, Jan Van Bogaert and Cor van Gelderen, for extra help with collecting material and constructive comments. Also to the responsible persons of various arboreta, botanic gardens and collections where I could collect herbarium specimens during the years; John Grimshaw for the 'New Trees' Maple account. NOTE: Imaged taxa are ordered alphabetical by sectio, following 'Maples of the World'.
Copyright © 2008–2015 Jan De Langhe. Non-commercial use of material with correctly referencing the name Jan De Langhe and the web address is allowed: http://www.plantentuin.ugent.be
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