Acer negundo (Box Elder)

Box Elder – Acer negundo: An In-depth Look

Acer negundo, commonly known as Box Elder, Boxelder Maple, or Manitoba Maple, is a fast-growing, short-lived deciduous tree native to North America. Recognized for its compound leaves and adaptability, Box Elder thrives in a variety of environments, from riparian zones to urban landscapes. While not as ornamental as other maples, it is valued for its resilience and ability to thrive in challenging landscapes.

Maple trees belong to the Sapindaceae family, which includes several popular ornamental trees such as Japanese Maple(Acer palmatum), Sugar Maple (Acer saccharum), Golden Rain Tree (Koelreuteria paniculata), Silver Maple (Acer saccharinum), and Horse Chestnut (Aesculus hippocastanum).

Native Range

Box Elder is native to North America, ranging from Canada to Honduras. It naturally grows in floodplains, along riverbanks, and in disturbed areas with ample moisture. Due to its adaptability, it has also naturalized in parts of Europe, South America, Australia, and Asia.

Plant Type and Habit

Boxelder Maple is a fast-growing, medium-sized deciduous tree with an irregular, rounded crown. It frequently forms multiple trunks or leaning branches, giving it a somewhat untamed appearance. This hardy, suckering tree has an upright growth habit and a broad, spreading canopy.

Size

At maturity, Box Elder typically grows 30-50 feet (9-15 m) in height with a similar spread. In optimal conditions, it can grow up to 2 feet (60 cm) or more per year. Fast Growing Trees for Small Yards and Large Gardens.

Lifespan

Box Elder has a relatively short lifespan, typically living 60-75 years, though some specimens can survive up to 100 years in favorable conditions.

Flowers and Fruits

Box Elder is a dioecious tree, meaning male and female flowers grow on separate trees. In early spring, before the leaves emerge, it produces small, yellow-green flowers. Male trees bear clusters of pollen-producing flowers, while female trees develop pendulous pale green racemes, followed by large, dangling clusters of pale yellow winged seeds (samaras). These samaras often remain on the tree well into winter, providing seasonal interest and a food source for wildlife.

Foliage

Unlike most maples, Box Elder has pinnately compound leaves measuring 6-15 inches long (15-37 cm), with 3-7 leaflets that resemble those of ash trees. The foliage is light green in summer and turns a dull yellow in fall.

Bark

The bark is pale gray or light brown with shallow ridges and furrows. Young stems are smooth and green, often with a waxy coating.

Hardiness

Box Elder thrives in USDA zones 3-9. It is highly adaptable to a range of soil types and moisture levels, tolerating periodic flooding and drought.

Uses and Landscaping Applications

• Ornamental: Often planted for quick shade in residential and urban settings. Its fast growth and adaptability make it a practical choice for streetscapes, parks, and naturalized areas.
• Shade Tree: Provides ample shade with its broad canopy, making it an excellent choice for backyards, playgrounds, and public spaces. Discover 32 Fast-Growing Shade Trees to Boost Your Garden’s Appeal
• Windbreak and Shelterbelt: Used to reduce wind erosion in agricultural landscapes and provide shelter for livestock and wildlife.
• Wildlife Habitat: Supports birds, pollinators, and mammals by providing food, shelter, and nesting sites. The seeds are an important food source for squirrels and songbirds.
• Riparian Restoration: Helps stabilize stream banks and prevent soil erosion in wetland and floodplain ecosystems. Its ability to tolerate wet soils makes it ideal for riparian buffer plantings.
• Woodland: Naturally occurs in mixed woodlands and disturbed forest edges. It is sometimes used in reforestation projects due to its rapid growth and adaptability.
• Pollinator Garden: Though not a primary nectar source, its flowers attract early-season pollinators such as bees and butterflies, supporting biodiversity.

Box Elder produces abundant sap, which can be used to make a mildly sweet beverage. Plains Native Americans traditionally harvested its sap for syrup, a practice still followed today. However, Box Elder syrup is less sweet than sugar maple syrup.

Wildlife Value

Box Elder provides essential food and shelter for various wildlife species. The seeds (samaras) are a valuable food source for many bird species, including finches and grosbeaks, as well as small mammals like squirrels and chipmunks. These seeds often persist into winter, offering sustenance when other food sources are scarce.

In addition to its seeds, Box Elder serves as a secondary browse species for mule deer and white-tailed deer, particularly in the fall. Young saplings and twigs may be browsed by deer and rabbits, making it an important part of the woodland food web.

The tree plays a crucial role in supporting pollinators and insects. Its flowers provide an early-season nectar source for bees and other pollinators, while its foliage serves as a host plant for the larvae of the Imperial Moth (Eacles imperialis).

Box Elder also attracts butterflies and serves as a habitat for various insects, which in turn provide food for insectivorous birds. Its broad canopy and dense foliage offer nesting sites and shelter for birds and small mammals, making it a vital tree for wildlife-friendly landscapes. Trees That Invite Wildlife to Your Garden.

Drought Tolerance

Box Elder is moderately drought-tolerant once established, though it thrives best in moist environments.

Deer and Rabbit Resistance

Young trees are susceptible to browsing by deer and rabbits, though mature trees have some resistance.

Toxicity

Box Elder seeds contain hypoglycin A, a toxin that can cause seasonal pasture myopathy in horses. The tree is not considered toxic to humans.

Invasiveness

Box Elder is considered invasive in some regions due to its rapid growth, prolific seeding, and ability to outcompete native vegetation. It has been widely planted in non-native areas of North America, Europe, and Asia, where it regenerates freely and spreads, particularly in riparian zones and urban landscapes. While it is invasive in much of its introduced range, its overall impact is generally not severe. In the temperate regions of the Southern Hemisphere, its spread is more limited.

Find where Box Elder is invasive in the United States.

Benefits and Drawbacks of Box Elder

Benefits

• Fast Growth Rate: Boxelder Maple grows quickly, making it an excellent choice for providing shade or establishing greenery in a short time.
• Adaptability: Thrives in a wide range of soil types, including poor, sandy, or clay soils. Tolerates wet, dry, and compacted conditions, making it suitable for urban and riparian environments.
• Erosion Control: Its extensive root system helps stabilize soil, particularly in floodplains or along riverbanks.
• Wildlife Habitat: Provides food and shelter for various wildlife species. Birds and small mammals feed on its seeds, while its canopy offers nesting sites.
• Low Maintenance: Requires minimal care once established and is resistant to drought.
• Reclamation Projects: Often used in land restoration or reclamation projects due to its ability to thrive in disturbed areas.
• Cold Hardiness: Tolerates extreme cold and is hardy in USDA zones 3-9.

Drawbacks

• Weak Wood: The wood of Boxelder Maple is brittle and prone to breakage during storms or high winds, which can pose safety hazards.
• Short Lifespan: Compared to other maples, it has a relatively short lifespan of 60-75 years.
• Invasive Potential: Prolific seed production allows it to spread aggressively in some regions, outcompeting native species.
• Pests and Diseases: Susceptible to boxelder bugs (Boisea trivittata), which can become a nuisance when they invade homes. Vulnerable to aphids, scale insects, and fungal diseases like powdery mildew and verticillium wilt.
• Messy Appearance: Produces large quantities of seeds (samaras) that litter the ground. Dropped branches and debris can create additional cleanup work.
• Low Ornamental Value: Lacks the vibrant fall color or attractive form of other maple species, making it less desirable as an ornamental tree.
• Aggressive Roots: The tree’s roots can interfere with nearby structures such as sidewalks, foundations, or sewer lines if planted too close.

How to Grow and Care for Box Elder

Choosing the Right Location

• Light: Box Elders grow best in full sun but can tolerate partial shade.
• Soil: They adapt to various soil types, including clay, loam, and sandy soils. The tree prefers moist, well-drained soil.
• Climate: Hardy in USDA zones 3-9, Box Elder is suitable for regions with extreme cold or heat.
• Tolerant to black walnut (Juglans nigra)

When to Plant

Plant in early spring or fall when the weather is cool and the soil is workable.

Planting Steps

• Dig a hole twice as wide as the root ball and slightly shallower than its height.
• Place the tree in the hole so that the top of the root ball is level with the ground.
• Backfill with native soil, firming it gently around the roots to eliminate air pockets.
• Water thoroughly after planting to help settle the soil.
• Mulch around the base of the tree to retain moisture and suppress weeds.
• Space trees at least 20 feet (6 M) apart to accommodate their spread.

Watering

• Water young trees regularly during their first year to establish deep roots.
• Mature trees are drought-tolerant but benefit from occasional deep watering during prolonged dry spells.

Fertilization

• Fertilize annually in early spring with a balanced fertilizer (e.g., 10-10-10) if soil nutrients are poor.
• Avoid over-fertilizing, as Box Elder grows rapidly without much additional input.

Pruning

• Timing: Prune in late winter or early spring while the tree is dormant.
• Purpose:
  • Remove dead, diseased, or damaged branches.
  • Thin out crowded areas to improve air circulation and reduce pest issues.
  • Shape young trees to develop a strong central leader and balanced structure.
  • Avoid heavy pruning of mature trees as their brittle wood may not recover well.

How To Propagate Box Elder

Seed Propagation

• Collect seeds (samaras) in late summer or early fall when they are mature.
• Stratify seeds by storing them in moist sand at 4°C (39°F) for 60-90 days to break dormancy.
• Sow seeds in well-draining soil outdoors in spring or indoors in pots under controlled conditions.

Cuttings

• Take softwood cuttings from young shoots in late spring or early summer.
• Dip cut ends into rooting hormone and plant them in moist potting mix.
• Keep cuttings in a warm, humid environment until roots develop.

Pests and Diseases

Common Pests

Boxelder Bugs

• Symptoms: Black and red insects that feed on seeds, leaves, and stems. While they rarely cause serious damage, they can become a nuisance when they invade homes in large numbers during the fall.
• Control: Remove fallen seeds to reduce their population. Seal cracks in buildings to prevent indoor infestations. Use insecticidal soap for outdoor control.

Aphids

• Symptoms: Suck sap from leaves, causing curling, yellowing, and stunted growth. They also produce sticky honeydew, leading to sooty mold.
• Control: Spray the tree with water to dislodge aphids or apply insecticidal soap or neem oil.

Scale insects

• Symptoms: Attach to branches and leaves, sucking sap and causing yellowing foliage and reduced vigor.
• Control: Treat infestations with horticultural oil or systemic insecticides.

Spider mites

• Symptoms: Fine webbing on leaves, stippling, or discoloration.
• Control: Spray leaves with water to dislodge mites or use miticides for severe infestations.

Borers

• Symptoms: Tunnel into the wood of stressed trees, causing wilting branches, exit holes in bark, and sawdust-like frass around the base.
• Control: Maintain tree health to prevent infestations. Remove affected branches and apply insecticides if necessary.

Common Diseases

Powdery mildew

• Symptoms: White powdery coating on leaves, leading to distorted growth and premature leaf drop.
• Causes: High humidity and poor air circulation.
• Control: Improve air circulation and apply fungicides like neem oil or sulfur-based treatments.

Canker Diseases

• Symptoms: Sunken dead areas on bark or stems that may girdle branches, causing dieback.
• Causes: Fungal infections often triggered by stress or injury.
• Control: Prune affected areas and improve overall tree health.

Root rot

• Symptoms: Wilting shoots, blackened roots, stunted growth, and poor vigor.
• Causes: Overwatering or poorly drained soil leading to fungal decay.
• Control: Improve drainage and avoid overwatering. Apply fungicides if necessary.

Leaf Spot Diseases

• Symptoms: Dark spots surrounded by yellow halos on leaves, leading to premature defoliation.
• Causes: Fungal pathogens exacerbated by wet conditions.
• Control: Remove affected leaves promptly and apply fungicides if needed.

Verticillium wilt

• Symptoms: Sudden wilting, yellowing leaves, branch dieback, and poor growth due to a soil-borne fungus affecting the vascular system.
• Control: There is no cure; focus on prevention by planting in well-drained soil.