red maple (Acer rubrum)

First place champion in Boulder.

Species info:

Leaves: Opposite, simple, 2–4 inches long and wide; typically with 3–5 lobes and finely serrated margins. Upper surface medium green; lower surface gray-green. Fall color ranges from yellow to orange-red to deep red, most vibrant in neutral to slightly acidic soils.

Leaflets: N/A (simple leaves)

Leaf Surface: Smooth and glossy above; dull and pale beneath.

Bark: Smooth and light gray when young, developing shallow furrows and ridges with age.

Flowers: Small, reddish-purple clusters appearing in early spring before leaves emerge.

Fruit: Paired winged samaras, often tinged red; mature in late spring to early summer.

Botanical: Acer rubrum

Family: Sapindaceae

Mature Height: Typically around 35 feet, though size varies by cultivar.

Canopy Spread: 25–35 feet, depending on cultivar.

Foliage Type: Deciduous

Tree Shape: Pyramidal or elliptical in youth, ovoid, rounded or irregular in maturity

Flowers: Inconspicuous

Fruit: None

Fall Color: Yellow to orange-red to bright red

Water Use: Moderate to high; prefers moist, well-drained soils; not drought-tolerant.

Hardiness: Zones 3–7 (depending on cultivar); recommended below 7,500 ft elevation.

Soil Preference: Best in neutral to slightly acidic soils; prone to chlorosis in alkaline conditions (pH > 7.4).

Wildlife Value: Attracts pollinators in spring; samaras eaten by birds and small mammals.

Pests/Pathogens: Generally pest-free.

Colorado Suitability: Performs best in older, established soils with moderate acidity; avoid planting in new developments or highly alkaline, compacted, or drought-prone sites.

Planting recommendation: Conditionally recommended for the Front Range, as it requires acidic soils

Information Sources:

• Michael Dirr, Manual of Woody Landscape Plants (University of Georgia, 1990)