Edward F. Gilman, Dennis G. Watson, Ryan W. Klein, Andrew K. Koeser, Deborah R. Hilbert and Drew C. McLean
Introduction
Silver maple has a vase shape and is a rapidly growing, fairly weak-wooded tree that reaches a height of 60 to 80 feet with a 5- to 6- foot diameter trunk on a moist site. The tree is useful in wet areas, transplants easily, and can grow where few others can. It should be saved for planting in wet areas or where nothing else will thrive. Roots often grow on the surface of the soil, making mowing grass difficult under the canopy. They also are aggressive, growing into septic tank drain fields and into broken water and sewer pipes. It is also hard to plant shrubs and other plants beneath the branches due to the dense root system.
Figure 1. Full Form - Acer saccharinum: silver maple Credit: Gitta Hasing, UF/IFAS
General Information
Scientific name: Acer saccharinum
Pronunciation: AY-ser sack-uh-RYE-num
Common name(s): silver maple
Family: sapindaceae
USDA hardiness zones: 3A through 9B (Figure 2)
Origin: native to eastern half of the United States and southeastern Canada
UF/IFAS Invasive Assessment Status: native
Uses: urban tolerant; shade; reclamation
Figure 2. Range
Description
Height: 60 to 80 feet
Spread: 40 to 60 feet
Crown uniformity: irregular
Crown shape: vase
Crown density: moderate
Growth rate: fast
Texture: medium
Foliage
Leaf arrangement: opposite/subopposite
Leaf type: simple
Leaf margin: incised, parted
Leaf shape: star-shaped
Leaf venation: palmate
Leaf type and persistence: deciduous
Leaf blade length: 2 ½ to 5 inches
Leaf color: darkgreen on top, silvery white underneath
Silver maple will grow in areas that have standing water for several weeks at a time. It grows best on acid soil, which remains moist, but adapts to very dry, alkaline soil. Leaves may scorch in areas with restricted soil space during dry spells in the summer but will tolerate drought if roots can grow unrestricted into a large soil volume.
Branches tend to droop, almost weep, forming a graceful canopy outline as it grows older. The bright yellow fall color can attract attention in early fall, but you will pay the price with the abundant number of leaves to rake. To develop a stronger, more durable tree, prune so that major limbs remain smaller than half the diameter of the trunk.
Silver maple can be a prolific seed producer giving rise to many volunteer trees. It often sends up sprouts from the trunk and branches, producing an unkempt appearance. Branches often form poor attachments with trunk resulting in branch failure in old, mature specimens. Frequent pruning is required to develop a strong branch structure. Ice and snow loads can cause branch failure in younger trees. Like many other large trees, it will lift sidewalks if improperly located too close to sidewalks. There are numerous insect and disease problems. There are too many other superior trees to warrant wide use of this species, but it does have its place in tough sites away from buildings and people. It grows extremely fast so creates almost instant shade, making this a popular tree among homeowners throughout its hardiness range.
Trees are susceptible to many pest problems but none so serious to warrant control.
There are a few cultivars but these also have weak wood: 'Pyramidale'—narrow crown; 'Silver Queen'—bright green leaves with lower leaf surfaces silvery; 'Skinneri'—somewhat weeping, pyramidal form, dissected leaves with a better branching habit; 'Weiri' —cutleaved form with pendulous branches. There is a recently introduced (1987) hybrid cross between red and silver maple called hybrid maple (Acer x fremanii). Cultivars of this hybrid include 'Armstrong Two' with a narrow columnar crown to 35 feet tall, 'Autumn Blaze' with an oval crown to 50 feet tall, 'Celebration' with a narrow upright crown and a strong central leader to 50 or 60 feet tall, 'Celzam' with a narrow oval crown to 50 feet tall, and 'Scarlet Sentenial' with great fall color and oval crown to 40 feet tall. The culture of these trees is probably similar to red maple.
Trees are propagated from seeds and from cuttings. Cultivars are best produced from cuttings.
Pests
Leaf stalk borer and petiole borer cause the same type of injury. Both insects bore into the leaf stalk just below the leaf blade. The leaf stalk shrivels, turns black, and the leaf blade falls off. The leaf drop may appear heavy but serious injury to a healthy tree is rare.
Gall mites stimulate the formation of growths or galls on the leaves. The galls are small but can be so numerous that individual leaves curl up. The most common gall is bladder gall mite found on silver maple. The galls are round and at first green but later turn red, then black, then dry up. Galls of other shapes are seen less frequently on other types of maples. Galls are not serious, so chemical controls are not needed.
Crimson erineum mite is usually found on silver maple and causes the formation of red fuzzy patches on the lower leaf surfaces. The problem is not serious so control measures are not suggested.
Aphids infest maples, usually Norway maple, and may be numerous at times. High populations can cause leaf drop. Another sign of heavy aphid infestation is honey dew on lower leaves and objects beneath the tree. Aphids are controlled by spraying or they may be left alone. If not sprayed, predatory insects will bring the aphid population under control.
Scales are an occasional problem on maples. Perhaps the most common is cottony maple scale. The insect forms a cottony mass on the lower sides of branches. Scales are usually controlled with horticultural oil sprays. Scales may also be controlled with well-timed sprays to kill the crawlers.
If borers become a problem it is an indication the tree is not growing well. Controlling borers involves keeping trees healthy. Chemical controls of existing infestations are more difficult. Proper control involves identification of the borer infesting the tree then applying insecticides at the proper time.
Diseases
Anthracnose is more of a problem in rainy seasons. The disease resembles, and may be confused with, a physiological problem called "scorch". The disease causes light brown or tan areas on the leaves. Anthracnose may be controlled by fungicides sprayed on as leaves open in the spring. Two additional sprays at two-week intervals will be needed. The disease is most common on sugar and silver maples and boxelder. Other maples may not be affected as severely. Sprays may need to be applied by a commercial applicator having proper spray equipment.
Verticillium wilt symptoms are wilting and death of branches. Infected sapwood will be stained a dark or olive green, but staining can't always be found. If staining cannot be found, do not assume the problem is not verticillium wilt. Severely infected trees probably can't be saved. Lightly infected trees showing only a few wilted branches may be pulled through. Fertilize and prune lightly infected trees. This treatment will not cure the problem but may allow the tree to outgrow the infection. Girdling roots will cause symptoms that mimic verticillium wilt.
Tar spot and a variety of leaf spots cause some concern among homeowners but are rarely serious enough for control.
Reference
Koeser, A. K., Hasing, G., Friedman, M. H., and Irving, R. B. 2015. Trees: North & Central Florida. University of Florida Institute of Food and Agricultural Sciences.
