Introduction
'Red Sunset' and `October Glory' have proven to be the best cultivars of red maple for the South. 'Red Sunset' has strong wood and is a vigorous, fast-grower, reaching a height of 50 feet with a spread of 25 to 35 feet. Trees are often seen shorter in the southern part of its range unless located on a wet site. This tree is preferred over red maple, silver maple, or boxelder when a fast-growing maple is needed, and will take on a pyramidal or oval silhouette. The newly emerging red flowers and fruits signal that spring has come. They appear in December and January in Florida, later in the northern part of its range. Leaves retain an attractive high gloss throughout the growing season. The seeds of 'Red Sunset' red maple are quite popular with squirrels and birds.
General Information
Scientific name: Acer rubrum
Pronunciation: AY-ser ROO-brum
Common name(s): 'Red Sunset' red maple
Family: Aceraceae
USDA hardiness zones: 4B through 8B (Fig. 2)
Origin: native to North America
Invasive potential: little invasive potential
Uses: reclamation; highway median; screen; shade; street without sidewalk; deck or patio; tree lawn 4–6 feet wide; tree lawn > 6 ft wide; specimen; bonsai
Availability: generally available in many areas within its hardiness range
Description
Height: 45 to 50 feet
Spread: 25 to 40 feet
Crown uniformity: symmetrical
Crown shape: upright/erect, oval
Crown density: moderate
Growth rate: fast
Texture: medium
Foliage
Leaf arrangement: opposite/subopposite (Fig. 3)
Leaf type: simple
Leaf margin: lobed, incised, serrate
Leaf shape: star-shaped
Leaf venation: palmate
Leaf type and persistence: deciduous
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: orange, red
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: red
Fruit characteristics: attracts squirrels/mammals; showy; fruit/leaves not a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; not showy; typically one trunk; thorns
Pruning requirement: needed for strong structure
Breakage: resistant
Current year twig color: reddish, gray
Current year twig thickness: medium
Wood specific gravity: 0.54
Culture
Light requirement: full sun, partial sun or partial shade
Soil tolerances: sand; loam; clay; acidic; well-drained; extended flooding
Drought tolerance: moderate
Aerosol salt tolerance: low
Other
Roots: can form large surface roots
Winter interest: yes
Outstanding tree: yes
Ozone sensitivity: unknown
Verticillium wilt susceptibility: susceptible
Pest resistance: resistant to pests/diseases
Use and Management
The outstanding ornamental characteristic of 'Red Sunset' red maple is the brilliant orange to red fall color lasting several weeks. 'Red Sunset' red maple is often one of the first trees to color up in autumn, and it puts on one of the most brilliant displays of any tree. 'Red Sunset' will color-up before 'October Glory'. In Auburn University's trials, it was rated the best cultivar of red maple for the South, although like other red maples there is occasional bark splitting on the southwest side of the trunk during the winter. It is one of the highest-rated trees in Ohio Shade Tree Evaluation trials. It is well suited as a street tree in northern and mid-southern climates in residential and other suburban areas.
The tree makes the best growth in wet or moist places and has no particular soil texture preference. However, chlorosis may develop on alkaline soil. The tree grows rapidly and has a dense canopy in the sun but opens up in partial shade. Irrigation is often needed to support street tree plantings in well-drained soil in the south. However, it appears to adapt to no irrigation in the south on a site where roots can explore an unlimited soil space. Roots do not often raise sidewalks as silver maples do, because of a slower growth rate and less aggressive root system. 'Red Sunset' red maple is easily transplanted and usually develops surface roots in soil ranging from well-drained sand to clay. It is not especially drought tolerant on sandy soils, particularly in the southern part of the range, although it has proven tolerant of clay soil.
Propagation is by grafting or cuttings but own-root cuttings are preferred to avoid graft-incompatibilities.
Pests
Aphids infest maples, usually Norway maple, and may be numerous at times. Usually not too serious on red maples. 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
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. Scorch symptoms are light brown or tan dead areas between leaf veins. 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 will 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.
Girdling roots grow around the base of the trunk rather than growing away from it. As both root and trunk increase in size, the root chokes the trunk. Girdling roots are detected by examining the base of the trunk. The lack of trunk flare at ground level is a symptom. The portion of the trunk above a girdling root does not grow as rapidly as the rest so may be slightly depressed. The offending root may be on the surface or may be just below the sod. The tree crown shows premature fall coloration and death of parts of the tree in more serious cases. If large portions of the tree have died it may not be worth saving. Girdling roots are functional roots so when removed a portion of the tree may die. When the girdling root is large the treatment is as harmful as the problem. After root removal, follow-up treatment includes watering during dry weather. The best treatment for girdling roots is prevention by removing or cutting circling roots at planting or as soon as they are detected on young trees.