Introduction

'Skinneri' silver maple is a fast-growing, weak-wooded tree that probably reaches a height of about 60 feet with a large trunk. It has a somewhat weeping, pyramidal growth form and the leaves are finely dissected, not resembling silver maple at all. Leaves almost appear as if they were injured with a herbicide, because they are so finely dissected. The tree is useful in wet areas, transplants easily and can grow where few others can grow. 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. It is also hard to plant shrubs and other plants beneath the canopy due to the dense root system.

General Information

Scientific name: Acer saccharinum

Pronunciation: AY-ser sack-uh-RYE-num

Common name(s): 'Skinneri' silver maple

Family: Aceraceae

USDA hardiness zones: 3B through 9B (Fig. 2)

Origin: native to North America

Invasive potential: weedy native

Uses: urban tolerant; shade; reclamation

Availability: somewhat available, may have to go out of the region to find the tree

Description

Height: 50 to 60 feet

Spread: 40 to 60 feet

Crown uniformity: irregular

Crown shape: pyramidal, weeping

Crown density: moderate

Growth rate: fast

Texture: fine

Foliage

Leaf arrangement: opposite/subopposite (Fig. 3)

Leaf type: simple

Leaf margin: parted

Leaf shape: star-shaped

Leaf venation: palmate

Leaf type and persistence: deciduous

Leaf blade length: 2 to 4 inches, 4 to 8 inches

Leaf color: green

Fall color: yellow

Fall characteristic: showy

Flower

Flower color: red

Flower characteristics: showy

Fruit

Fruit shape: elongated

Fruit length: 1 to 3 inches

Fruit covering: dry or hard

Fruit color: green, brown

Fruit characteristics: does not attract wildlife; showy; fruit/leaves a litter problem

Trunk and Branches

Trunk/bark/branches: branches droop; not showy; typically one trunk; thorns

Pruning requirement: needed for strong structure

Breakage: susceptible to breakage

Current year twig color: reddish, brown

Current year twig thickness: thin, medium

Wood specific gravity: 0.47

Culture

Light requirement: full sun, partial sun or partial shade

Soil tolerances: sand; loam; clay; acidic; well-drained; extended flooding

Drought tolerance: high

Aerosol salt tolerance: moderate

Other

Roots: can form large surface roots

Winter interest: no

Outstanding tree: no

Ozone sensitivity: unknown

Verticillium wilt susceptibility: susceptible

Pest resistance: resistant to pests/diseases

Use and Management

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.

Like many other large trees, it will lift sidewalks if improperly located too close to sidewalks. Locate well away from septic tanks and drain fields, since roots extend about three times the distance from the trunk to the edge of the branches. There are too many other superior trees to warrant wide use of this tree, particularly in urban areas. Silver maple is best saved for wet sites or for naturalizing in an area away from urban structures. If you must plant a silver maple, this is one of the nicest.

Silver maple is notorious for developing weak branch crotches, and the wood is brittle. Be sure to prune major limbs so they remain less than half the diameter of the trunk. This will make the structure stronger and help the tree to live longer.

Pests

Gall mites can 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.

There are many others insect problems which can affect Silver Maple.

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 can not 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.

Scorch occurs during periods of high temperatures accompanied by wind, particularly in areas with limited soil space where roots cannot expand into a large soil volume. Trees with diseased or inadequate root systems will also show scorching. When trees do not get enough water they scorch. Scorch symptoms are light brown or tan dead areas between leaf veins and at the tips of the leaf. The symptoms are on all parts of the tree or only on the side exposed to sun and wind. Scorching due to dry soil may be prevented by watering. If scorching is due to an inadequate or diseased root system, watering may have no effect.

Nutrient deficiency symptoms are yellow or yellowish-green leaves with darker green veins. The most commonly deficient nutrient on maple is manganese. Implanting capsules containing a manganese source in the trunk will alleviate the symptoms. Test soil samples to determine if the soil pH is too high for best manganese availability. Plants exposed to weed killers may also show similar symptoms.