Acidic Soil, Mulch & Red Maples

Red Maple Features

• Red maples grow to reach between 40 and 60 feet tall and 25 to 35 feet wide in urban settings, but can achieve 120 feet or more in the wild. They are named for their vibrant red fruit and flowers, though their crimson or wine-colored fall leaf displays are also prized by landscapers. They have a narrow or rounded crown with oppositely arranged leaves. Each leaf has three-pointed lobes separated by shallow sinuses. Red maple bark is smooth and gray when the tree is young and thicker with small fissures at maturity.

Red Maples and Acidic Soil

• Most maples prefer slightly acidic, moist, fertile and well-drained soil, but this is particularly true for the red maple. Nutrient deficiencies and root problems, such as poor growth, chlorosis and dieback, can be a problem for this tree in alkaline soil. The pH of soil can affect how well a tree absorbs nutrients; while essential nutrients may be present in the soil, alkaline conditions can prevent the tree from taking them up. Alkaline soil can also prevent symbiotic mycorrhizae fungi from forming around the roots, which help them absorb important minerals.

Chlorosis

• Maple and birches are particularly susceptible to chlorosis, a nutrient deficiency that can be traced back to alkaline soil in many cases. Chlorosis produces bright yellow to pale yellow-green leaves in which the veins may or may not remain green. In severe chlorosis, the leaves scorch, or turn brown along the edges. This condition is usually caused by a lack of nutrients, often iron or manganese, which may be present in the soil but unavailable to the tree due to alkaline conditions.

Red Maples and Mulch

• Red maples are known for their shallow root structure; feeding roots often protrude above the surface and can raise sidewalks. Turf should not be grown under red maples, according the Clemson University Cooperative Extension, nor would it probably survive. Feeding roots need proper water and air exchange, and any attempt to mow the turf would result in damage to the tree and the lawn equipment. To cover surface roots, use 3 to 4 inches of organic mulch or permeable materials offered by gardening centers as mulch alternatives. Covering the roots with soil can suffocate them, killing the tree.