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RED MAPLE - Acer rubrum



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Distinguishing features

Maples are out only trees with simple, opposite, fan-lobed leaves. The red maple's leaves have 3-5 lobes with realtively shallow notches and are silvery white beneath. Twigs, buds, and flowers are reddish but the leaves are green. It is common to have groups of buds on side leaf scars (characteristic of red maple). Young trunk bark is smooth and gray; older bark is broken and dark. Height 20-40 feet; diameter 1-2 feet.

Description. Red maple is a typical maple with opposite simple leaves.  The leaves are broad and have three to five lobes with palmately arranged veins.  The fruit is a two-winged, two-seeded structure; the wings form a V" and the two seeds lie at the bottom of the V.
Geographic range.  Red maple ranges naturally over the entire eastern United States and grows  on well-drained or moist, swampy soils.  It may be a pest species in cut-over areas such as utility rights-of-way or deforested pasture lands.  It is also grown as a cultivated ornamental tree.
Toxic principle has not been identified, but it causes acute hemolysis.  In vitro evidence suggests that tannins may be responsible for the RBC lysis.

Toxicity.  Fresh, wilted and dried leaves are toxic and ingestion of as little as 0.3 % of the body weight as leaves is toxic to horses.


Clinical signs are typical of acute hemolytic disease: depression, icterus, anemia,

hemoglobinemia and hemoglobinuria.  Polypnea and tachycardia may result from severe anemia and cyanosis may also be present.

Laboratory diagnosis of blood reveals a low packed cell volume (PCV), mild methemoglobinemia, Heinz bodies, hyperbilirubinemia and sometimes, increased creatine phosphokinase.

Lesions are consistent with damage caused by hemolysis and hypoxia.  Gross lesions can include generalized icterus, splenomegaly and severe, diffuse congestion of kidneys.  Histologic lesions include tubular nephrosis with hemoglobin casts, centrilobular hepatic degeneration and necrosis and phagocytized RBCs and hemosiderin in the spleen, liver and adrenal glands.

Treatment is completely supportive, because there is no antidote.

      A whole blood transfusion may be life-saving.

       Intravenous fluids and diuresis to reduce the probability of hemoglobin nephrosis may be helpful.

Prevention. Do not plant red maples near horse pastures.  Remove existing red maples in or near pastures.

While there are no documented cases of other Acer sp. causing intoxication, they should be considered a potential problem until proven otherwise.  Thus, access of horses to silver and sugar maples should be restricted.


Copyright 2002

University of Pennsylvania
Created by:    Alexander Chan (2003), Daphne Downs (2002), Chris Tsai (2001), Brett Begley (2000), Janet Triplett (1997)
Faculty Advisor:  Dr. Robert Poppenga