Editing Acer rubrum (section)

== Ecology ==
Red maple's maximum lifespan is 150 years, but most live less than 100 years. The tree's thin bark is easily damaged from ice and storms, animals, and when used in landscaping, being struck by flying debris from lawn mowers, allowing fungi to penetrate and cause heart rot.<ref name="Silvics" /> Its ability to thrive in a large number of habitats is largely due to its ability to produce [[root]]s to suit its site from a young age. In wet locations, red maple seedlings produce short [[taproot]]s with long, well-developed lateral roots; while on dry sites, they develop long taproots with significantly shorter laterals. The roots are primarily horizontal, however, forming in the upper {{convert|25|cm|in|abbr=on}} of the ground. Mature trees have woody roots up to {{convert|25|m|ft|abbr=on}} long. They are very tolerant of flooding, with one study showing that 60 days of flooding caused no leaf damage. At the same time, they are tolerant of drought due to their ability to stop growing under dry conditions by then producing a second-growth flush when conditions later improve, even if growth has stopped for 2 weeks.<ref name="Silvics" />

[[File:Maplekeys.jpg|left|thumb|Samaras from a specimen in [[Milford, New Hampshire]]]]
''A. rubrum'' is one of the first plants to flower in spring. A crop of seeds is generally produced every year with a bumper crop often occurring every second year. A single tree between {{convert|5|and|20|cm|in|abbr=on}} in diameter can produce between 12,000 and 91,000 seeds in a season. A tree {{convert|30|cm|ft|abbr=on}} in diameter was shown to produce nearly a million seeds.<ref name="Silvics" /> Red maple produces one of the smallest seeds of any of the maples.<ref name="Miller" /> Fertilization has also been shown to significantly increase the seed yield for up to two years after application.

The seeds are [[epigeal germination|epigeal]] and tend to germinate in early summer soon after they are released, assuming a small amount of light, moisture, and sufficient temperatures are present. If the seeds are densely shaded, then germination commonly does not occur until the next spring. Most seedlings do not survive in closed [[canopy (biology)|forest canopy]] situations. However, one- to four-year-old seedlings are common under dense canopy. Though they eventually die if no light reaches them, they serve as a reservoir, waiting to fill any open area of the canopy above.

Trees growing in a Zone 9 or 10 area such as Florida will usually die from cold damage if transferred up north, for instance to Canada, Maine, Vermont, New Hampshire and New York, even if the southern trees were planted with northern red maples. Due to their wide range, genetically the trees have adapted to the climatic differences.

[[File:2016-03-02 17 22 36 Female Red Maple blossoms along McLearen Road (Virginia State Secondary Route 668) in Oak Hill, Fairfax County, Virginia.jpg|thumb|Female flowers with red pistils protruding]]
Red maple is able to increase its numbers significantly when associate trees are damaged by disease, cutting, or fire. One study found that 6 years after [[clearcutting]] a {{convert|3.4|ha|acre|abbr=off}} Oak-Hickory forest containing no red maples, the plot contained more than 2,200 red maple seedlings per hectare (900 per acre) taller than {{convert|1.4|m|ft|abbr=on}}.<ref name="Silvics" /> One of its associates, the [[black cherry]] (''Prunus serotina''), contains benzoic acid, which has been shown to be a potential [[allelopathic]] inhibitor of red maple growth. Red maple is one of the first species to start stem elongation. In one study, stem elongation was one-half completed in 1 week, after which growth slowed and was 90% completed within only 54 days. In good light and moisture conditions, the seedlings can grow {{convert|30|cm|ft|abbr=on}} in their first year and up to {{convert|60|cm|ft|abbr=on}} each year for the next few years, making it a fast grower.<ref name="Silvics" />

[[File:Rubrum buds.jpg|thumb|Flowerbuds in spring before blooming]]
The red maple is used as a food source by several forms of wildlife. [[Elk]] and [[white-tailed deer]] in particular use the current season's growth of red maple as an important source of winter food. Several [[Lepidoptera]] (butterflies and moths) utilize the leaves as food, including larvae of the rosy maple moth (''[[Dryocampa rubicunda]]''); see List of Lepidoptera that feed on maples.

Due to ''A. rubrum''{{'}}s very wide range, there is significant variation in hardiness, size, form, time of flushing, onset of dormancy, and other traits. Generally speaking, individuals from the north flush the earliest, have the most reddish fall color, set their buds the earliest and take the least winter injury. Seedlings are tallest in the north-central and east-central part of the range. In Florida, at the extreme south of the red maple's range, it is limited exclusively to swamplands. The fruits also vary geographically with northern individuals in areas with brief, frost-free periods producing fruits that are shorter and heavier than their southern counterparts. As a result of such variation, there is much genetic potential for breeding programs with a goal of producing red maples for cultivation. This is especially useful for making urban [[cultivar]]s that require resistance from [[verticillium wilt]], air pollution, and drought.<ref name="Silvics" />

[[File:Autumn Blaze Maple in Toronto.jpg|right|thumb|upright=0.72|''Acer × freemanii'' 'Jeffersred' in Toronto]]
Red maple frequently hybridizes with [[silver maple]]; the [[Hybrid (biology)|hybrid]], known as Freeman's maple, ''[[Acer × freemanii]]'', is intermediate between the parents.

=== Allergenic potential ===
[[File:2015-04-12 16 31 55 Male Red Maple flowers on Bayberry Road in Ewing, New Jersey.jpg|thumb|Male flowers]]
The allergenic potential of red maples varies widely based on the cultivar.

The following cultivars are completely [[male]] and are highly allergenic, with an [[OPALS (Ogren Plant Allergy Scale)|OPALS]] allergy scale rating of 8 or higher:<ref name=Ogren>{{cite book|last1=Ogren|first1=Thomas|title=The Allergy-Fighting Garden|date=2015|publisher=Ten Speed Press|location=Berkeley, CA|isbn=978-1-60774-491-7|pages=54–55}}</ref>

* 'Autumn Flame' ('Flame')
* 'Autumn Spire'
* 'Columnare' ('Pyramidale')
* 'Firedance' ('Landsburg')
* 'Karpick'
* 'Northwood'
* 'October Brilliance'
* 'Sun Valley'
* 'Tiliford'

The following cultivars have an OPALS allergy scale rating of 3 or lower; they are completely [[female]] trees, and have low potential for causing allergies:<ref name="Ogren" />

* 'Autumn Glory'
* 'Bowhall'
* 'Davey Red'
* 'Doric'
* 'Embers'
* 'Festival'
* 'October Glory'
* 'Red Skin'
* 'Red Sunset' ('Franksred')

=== Toxicity ===
The leaves of red maple, especially when dead or wilted, are extremely [[List of plants poisonous to equines|toxic to horses]]. The toxin is unknown, but believed to be an [[oxidant]] because it damages [[red blood cell]]s, causing acute [[hemolysis|oxidative hemolysis]] that inhibits the transport of [[oxygen]]. This not only decreases oxygen delivery to all tissues, but also leads to the production of [[methemoglobin]], which can further damage the kidneys. The ingestion of 700&nbsp;grams (1.5 pounds) of leaves is considered toxic and 1.4 kilograms (3 pounds) is lethal. Symptoms occur within one or two days after ingestion and can include depression, lethargy, increased rate and depth of breathing, increased heart rate, [[jaundice]], dark brown urine, [[horse colic|colic]], [[laminitis]], coma, and death. Treatment is limited and can include the use of [[methylene blue]] or mineral oil and [[activated carbon]] in order to stop further absorption of the toxin into the stomach, as well as [[blood transfusion]]s, fluid support, [[diuretic]]s, and anti-oxidants such as [[Vitamin C]]. About 50% to 75% of affected horses die or are euthanized as a result.<ref name="Purdue">{{cite web | last =Goetz | first =R. J. |   title =Red Maple Toxicity | work = Indiana Plants Poisonous to Livestock and Pets | publisher = Purdue University | url =http://vet.purdue.edu/depts/addl/toxic/plant50.htm |   access-date =9 May 2007 |archive-url = https://web.archive.org/web/20070505101113/http://vet.purdue.edu/depts/addl/toxic/plant50.htm |archive-date = May 5, 2007}}</ref>