Acer rubrum (ay’-sir ru’-brum)
Family: Sapindaceae, Soapberry

Key Steps

• 1a – Opposite leaf arrangement on stem — go to 2
  • 2a – Leaf simple — go to 3
    • 3a – Leaves are lobed — go to 4
      • 4b – No milky sap — go to 5
        • 5b – Margins of lobes are toothed — go to 7
          • 7a – Three to five lobes — go to 8
            • 8b – Lobes fairly similar in size. Base of middle lobe is wide. Sinuses are V-shaped and toothed — go to 10
              • 10a – Cultivated tree; single trunk. Leaves more than 3 inches wide — Red Maple

Description

Leaf: Usually 3 lobes, rarely 5. Base of middle lobe is wide. Sinuses are slightly toothed and not deep. Bright green above, light silvery gray and hairy veins beneath. Petioles often red.

Bud: Rounded and slightly hairy bud scale margins. Round flower buds are clustered, bright red.

Leaf Scar: Narrow.

Stem: Slender, bright red in winter, greenish-red in summer. Older stems grayish. Stems do not smell.

Pith: Solid, white.

Bark: Young: smooth, light gray. Older: dark gray and rough; does not flake off as much as silver maple.

Flower: Red, blooming before leaves appear. Short dense clusters. Petals.

Fruit: 2-3 inch long double samara, wings spreading at 60° angle.

Habit: Large shade tree, spreading branches, to 40+ feet tall.

Culture: Due to iron chlorosis (yellowing of leaves with veins remaining green) avoid planting on alkaline soils. High moisture preferred.

Resources

• Identifying Broadleaf Flowering Trees and Shrubs, CMG GardenNotes #173
• List of trees in this key
• Glossary of Terms
• Front Range Tree Recommendation List
• Online CSU Extension publications on Tree and Shrub Selection