Family:
Aceraceae
Toxins:
tannins gallic-acid
Flower Color:
  • flower color
  • flower color
  • flower color
  • flower color
Found:
ornamental, woodlands, waterside, fields, shade, pastures

Time of Greatest Risk

JFMAMJJASOND

Geographical Distribution

Red maple distribution - United States

Red Maple

Acer rubrum

Swamp Maple, Scarlet Maple, Curled Maple, Soft Maple
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Red maple (Acer rubrum) is a medium to large, deciduous, conical or oval-shaped tree from the Sapindaceae family. It is native to the northeastern United States and Canada, and is often found in or near pastures where horses are kept.
Red maple trees are well-known for their vivid leaf color change during the autumn, where leaves turn from green into various shades of red, orange, and yellow. There are many different varieties of red maple trees, and it is one of the most widely distributed tree species in eastern North America. Red maple is often one of the first trees to change color in the autumn.

Common Red Maple Varieties

Common NameShapeHeight (ft)Width (ft)Leaf shapeLeaf colorBark
Armstrong Red MapleColumnar50 to 6015 to 25Lobed and PalmateGlossy medium green, redLight gray, scaly
Autumn Flame Red MapleRounded45 to 5035 to 50PalmateMedium green, red or orangeDark gray, exfoliating or scaly
Bowhall Red MapleColumnar45 to 5015 to 20Lobed and PalmateGreen, red, gold or orangedark brown, fissured
Columnare Red MapleColumnar or pyramidal40 to 5015 to 20Lobed and PalmateGlossy medium green, redLight gray, scaly
Franksred Red MapleRounded45 to 5030 to 40PalmateMedium green, red or orangeDark gray, exfoliating or scaly
Gerling Red MapleConical30 to 3525 to 35Lobed and PalmateGlossy medium green, redLight gray, scaly
Northwood Red MapleRounded40 to 6025 to 40Lobed and PalmateGlossy medium green, redLight gray, scaly
October Glory Red MapleOval or rounded40 to 5025 to 35Lobed and PalmateGreen, red, gold or orangeGray to brown, rough or smooth
Red Sunset Red MapleColumnar45 to 5025 to 40PalmateMedium green, red or orangeDark gray, exfoliating or scaly
Autumn Blaze Red MapleRounded55 to 6530 to 40PalmateMedium green, red or orangeDark gray, exfoliating or scaly
Ingestion of partially wilted or dried red maple leaves is very toxic to horses, and it is one of the most common plant-associated poisonings in horses. Between 1981 and 2006, there has been more than 81 documented cases of Red maple toxicosis in horses living in the United States, caused by ingestion of wilted red maple leaves. The severity depends on the amount ingested, stage of decomposition of the leaves, species, tree age, horse age, and overall health status of the horse.

Toxic compounds
The toxic compounds responsible for causing Red maple toxicosis in horses are gallic acid and tannins (gallotannins) from the leaves of the red maple tree. The metabolism of the gallotannins and free gallic acid to pyrogallol by intestinal organisms such as K. pneumoniae and E. cloacae. These substances cause oxidative damage to horses' red blood cells, leading to methemoglobinemia and hemolytic anemia.

Increased risk of occurrence
Red maple leaves are most toxic when they are wilted, and decrease in toxicity as they dry. Horses are more likely to consume wilted red maple leaves following storms, since red maple tree branches are not very strong, they are more likely to fall, resulting in scattered piles of red maple leaves right where horses graze.