May 2, 2016

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Acer rubrum – Red Maple

Red maple, one of the “soft” maples is a native, common tree in the wilds of Minnesota. Prized tree for it’s fall color and beautiful form.
Medium tree height: 40-50′
Canopy spreads: 20-40′, Oval crown.
Drought Tolerance: Intolerant Shade Tolerance
Shade Tolerance Tolerant
Soil pH Tolerance Intolerant to high pH
Poor Soil Drainage Tolerant to flooding
Salt Tolerance Sensitive to salt spray and Intermediate in tolerance to soil salts.
There are several varieties to be found in the nurseries: “Firedance”, “Northwood”, “Northfire”, and “Red Sunset” to name a few. Red maple is common as a street tree, in yards and parks. Prefers soils that are moist and slightly acid, not the best choice for hot, dry soils of narrow boulevards.

Did you know
Donald Peattie states: “If Red Maple were as valuable a timber tree as Hard Maple, it would, with its immense range and abundance, be a national resource of the first class…”

Disease Management
Anthracnose, Discula species and others Fungi Tan/brown/black spots and blotches develop on leaves during wet periods. Spring infections result in leaf distortion. Necrosis may follow the veins. Rake up and destroy or compost fallen leaves. Promote tree vigor. Not seriously damaging to healthy established trees.

CHEMICAL: Preventative fungicides should be applied beginning at bud break when deemed necessary. Bordeaux, chlorothalonil, fixed coppers, mancozeb, thiophanate-methyl or zyban.

Leaf spot, Phyllosticta minima Fungi Well-defined lesion on the leaf surface with a light-colored center and dark margin at maturity. Tiny black dots (fruiting bodies of the fungus) are often visible. Rake up and destroy fallen leaves. Avoid wetting the tree foliage during irrigation. Promote tree vigor. Seldom damaging to healthy, established trees.

CHEMICAL: Treat preventatively with Bordeaux 8-8-100, fixed coppers or mancozeb.

Target-shaped canker, Nectria galligena, Eutypella parasitica Fungi Perennial cankers develop around wounds on immature trees, usually within 10 feet of the ground. The trunk is swollen around the canker, which often has a ãtarget-likeä appearance. Plant on good sites in proper zone. Prevent damage to trunk and limbs. Promote tree vigor. Remove branches with cankers. May become a hazard tree and should be evaluated as such.


Tar spot, Rhytisma acerinum Fungi Roughly circular, raised black spots on the leaf surface which resemble spots of tar. Seldom a problem. Maintain tree vigor. Infected leaves can be raked up and destroyed or composted.

CHEMICAL: None necessary.

Wilt, Verticillium dahliae Fungi Slow growth, dwarfed foliage and/or wilting. Leaves with scorched margins. Defoliation. Often occurs on only one part of the tree. Green to black vascular discoloration may be present in the sapwood of larger branches and the trunk. REFERENCE: Verticillium Wilt of Trees and Shrubs, AG-FO-1164 (MN), Deciduous Tree Diseases, PP-697 (ND). Fertilize to promote growth; keep nitrogen to a minimum. Prevent moisture stress. Remove dead limbs. Do not plant susceptible tree species where Verticillium is present in the soil.

CHEMICAL: None. NURSERY: Preplant fumigation.