Editing Acer rubrum (section)

== Description ==
[[File:Redmaplefoliage.jpg|thumb|Typical fall foliage in red maple country]]
Though ''A. rubrum'' is sometimes easy to identify, it is highly changeable in morphological characteristics. It is a medium to large sized tree, reaching heights of {{convert|27|to|38|m|ft|-1|abbr=on}} and exceptionally over {{convert|41|m|ft|abbr=on}} in the southern Appalachians where conditions favor its growth. The leaves are usually {{convert|9|to|11|cm|in|frac=4|abbr=on}} long on a full-grown tree. The trunk diameter often ranges from {{convert|46|to|88|cm|in|abbr=on}}; depending on the growing conditions, however, open-grown trees can attain diameters of up to {{Convert|153|cm|in|abbr=on}}. The trunk remains free of branches until some distance up the tree on forest grown trees, while individuals grown in the open are shorter and thicker with a more rounded crown. Trees on poorer sites often become malformed and scraggly.<ref name="VT">{{cite web | last =Seiler | first =John R. | author2 =Jensen, Edward C. | author3 =Peterson, John A. | title =Acer rubrum Fact Sheet | work =Virginia Tech Dendrology Tree Fact Sheets | publisher =Virginia Tech | url =http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=1 | access-date =23 May 2019}}</ref> Generally the crown is irregularly ovoid with ascending whip-like curved shoots. The [[Bark (botany)|bark]] is a pale grey and smooth when the individual is young. As the tree grows the bark becomes darker and cracks into slightly raised long plates.<ref name="Mitchell" /> The largest known living red maple is located near [[Armada, Michigan]], at a height of {{convert|38.1|m|ft|abbr=on}} and a bole circumference, at breast height, of {{convert|4.95|m|ftin|abbr=on}}.<ref name="Silvics">{{Silvics |last1=Walters |first1=R. S. |last2=Yawney |first2=H. W. |volume=2 |genus=Acer |species=rubrum | access-date=9 May 2007}}</ref>

[[File:Acer rubrum.jpg|thumb|Leaves on a branchlet from a specimen in northern Florida]]
The [[leaf|leaves]] of the red maple offer the easiest way to distinguish it from its relatives. As with all North American maple trees, they are [[deciduous]] and arranged oppositely on the twig. They are typically {{convert|5|–|10|cm|in|0|abbr=on}} long and wide with three to five [[palmate lobe]]s with a serrated margin. The [[sinus (botany)|sinuses]] are typically narrow, but the leaves can exhibit considerable variation.<ref name="VT" /> When five lobes are present, the three at the terminal end are larger than the other two near the base. In contrast, the leaves of the related [[silver maple]], ''A. saccharinum'', are much more deeply lobed, more sharply toothed, and characteristically have five lobes. The upper side of ''A. rubrum''{{'}}s leaf is light green and the underside is whitish and can be either [[glaucous]] or hairy. The leaf stalks are usually red and are up to {{convert|10|cm|in|0|abbr=on}} long. The leaves can turn a characteristic brilliant red in autumn, but can also become yellow or orange on some individuals. Soil acidity can influence the color of the foliage and trees with female flowers are more likely to produce orange coloration while male trees produce red. The [[Autumn leaf color|fall colors]] of red maple are most spectacular in the northern part of its range where climates are cooler.

[[File:Red striped and sugar maple leaves.jpg|thumb|''A. rubrum'' leaf in the autumn, top, compared to [[striped maple]], which turns yellow, and [[sugar maple]], which tends to orange.]]
The [[twig]]s of the red maple are reddish in color and somewhat shiny with small [[lenticel]]s. Dwarf shoots are present on many branches. The [[bud]]s are usually blunt and greenish to reddish in color, generally with several loose scales. The lateral buds are slightly stalked, and in addition, collateral buds may be present, as well. The buds form in fall and winter and are often visible from a distance due to their large size and reddish tint. The leaf scars on the twig are V-shaped and contain three bundle scars.<ref name="VT" />

[[File:Acer rubrum drummondii drawing.png|right|thumb|Drawing showing male and female flower, leaf and samara]]
The [[flower]]s are generally unisexual, with male and female flowers appearing in separate [[Sessility (botany)|sessile]] clusters, though they are sometimes also bisexual. They appear in late winter to early spring, from December<ref>{{cite web |url=https://edis.ifas.ufl.edu/pdffiles/ST/ST04100.pdf |title=Acer rubrum: Red Maple |publisher=Institute of Food and Agricultural Sciences Extension, University of Florida |first1=Edward F. |last1=Gilman |first2=Dennis G. |last2=Watson |first3=Ryan W. |last3=Klein |first4=Andrew K. |last4=Koeser |first5=Deborah R. |last5=Hilbert |first6=Drew C. |last6=McLean |access-date=June 18, 2019}}</ref> to May depending on elevation and latitude, usually before the leaves. The tree itself is considered [[polygamodioecious]], meaning some individuals are male, some female, and some [[monoecious]].<ref name="Silvics" /> Under the proper conditions, the tree can sometimes switch from male to female, male to hermaphroditic, and hermaphroditic to female.<ref>{{Cite journal|last1=Primack|first1=R.B.|last2=McCall|first2=C.|year=1986|title=Gender Variation in Red Maple Populations (Acer rubrum; Aceraceae): A Seven-Year Study of a "Polygamodioecious" Species|journal=American Journal of Botany|volume=73|issue=9|pages=1239–1248|doi=10.2307/2444057|jstor=2444057}}</ref> The red maple will begin blooming when it is about 8 years old, but it significantly varies between tree to tree: some trees may begin flowering when they are 4 years old. The flowers are red with 5 small petals and a 5-lobed [[calyx (botany)|calyx]], usually at the twig tips. The staminate flowers are [[sessile (botany)|sessile]]. The pistillate flowers are borne on [[pedicel (botany)|pedicels]] that grow out while the flowers are blooming, so that eventually the flowers are in a hanging cluster with stems {{cvt|1/2|to|2|in|cm|0|order=flip}} long.<ref>{{Illinois Wildflowers|trees/plants/red_maple|Red Maple (Acer rubrum)|access-date=6 June 2023|html=true}}</ref> The petals are lineal to oblong in shape and are pubescent. The pistillate flowers have one [[pistil]] formed from two fused carpels with a glabrous superior ovary and two long [[Style (botany)|styles]] that protrude beyond the [[perianth]]. The staminate flowers contain between 4 and 12 [[stamen]]s, often with 8.<ref name="Ontario">{{cite web | last =Goertz | first =D. | title =Acer rubrum plant description | publisher = Northern Ontario Plant Database | url =http://www.northernontarioflora.ca/description.cfm?speciesid=1000050 | access-date =10 May 2007}}</ref>

The [[fruit]] is a [[schizocarp]] of 2 [[Samara (fruit)|samaras]], each one {{convert|15|to|25|mm|in|frac=8|sp=us|abbr=on}} long. Prior to dehiscence, the wings of the fruit are somewhat divergent at an angle of 50 to 60°. They are borne on long slender pedicels and are variable in color from light brown to reddish.<ref name="VT" /> They ripen from April through early June, before even the leaf development is altogether complete. After they reach maturity, the seeds are dispersed for a 1- to 2-week period from April through July.<ref name="Silvics" />