Red Maple
Acer rubrum · Swamp MapleUSDA | Grow Zone
3-9Outdoors all year in zones 3 to 9. Anywhere colder, keep it as a houseplant.
- Light
- Full sun to partial shade
- Water
- Consistently moist soil
- Humidity
- 40-70% humidity
- Temperature
- 60-75°F (15-24°C)
- Difficulty
- Intermediate
- Growth
- Moderate
- Mature size
- 40-60 ft tall
Acer rubrum, commonly known as Red Maple or Swamp Maple, is a beautiful deciduous tree native to North America. Renowned for its brilliant red fall foliage, it thrives in a variety of soil types and is a popular choice for landscaping due to its adaptability and aesthetic appeal.
Ask Vesper about Red Maple
Ideal temperature
60-75°F is where it grows fastest.
Spacing and harvest
- Mature size
- 40-60 ft tall
- Plant apart
- 30-40 in
- Frost
- Hardy: survives frost
Everything it needs
9 essentials at a glance
Watering
Acer rubrum prefers consistently moist soil, especially during its growing season.
Water deeply once a week, increasing frequency during hot, dry spells. In spring and summer, ensure the top 1-2 inches of soil remain moist. Signs of over-watering include yellowing leaves and root rot, while under-watering may cause wilting and leaf drop.
Light
This tree thrives in full sun to partial shade.
Ideally, it should receive at least 6 hours of direct sunlight daily. While it can tolerate some shade, too much can hinder its growth and vibrant fall color. Ensure it is planted in a location where it can receive morning sun and some afternoon shade.
Soil
Acer rubrum prefers well-draining, loamy soil with a pH range of 5.0 to 7.0.
It benefits from organic matter mixed into the soil to improve drainage and nutrient content. Avoid heavy clay soils that retain water, as they can lead to root problems.
Humidity
This tree enjoys moderate to high humidity levels, ideally between 40-70%.
To increase humidity, consider misting the leaves or placing a humidifier nearby. Signs of low humidity stress include browning leaf tips and leaf drop.
Temperature
Acer rubrum thrives in temperatures ranging from 60-75°F (15-24°C) and is hardy in USDA zones 3-9.
It can tolerate cold temperatures down to -30°F (-34°C) but may struggle in extreme heat above 90°F (32°C). Protect young trees from harsh winter winds.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10 or 12-12-12.
Fertilize in early spring before new growth begins, applying every 4-6 weeks during the growing season. Signs of nutrient deficiency include stunted growth, pale leaves, and poor fall color.
Pruning
Prune Acer rubrum in late winter or early spring before new growth starts.
Use sharp, clean pruning shears to remove dead or crossing branches, and shape the tree to encourage an open canopy. Deadheading is not necessary for this species.
Repotting
If grown in a container, repot every 2-3 years or when roots begin to emerge from the drainage holes.
Choose a pot that is 1-2 inches larger in diameter. Signs it needs repotting include root crowding and poor growth. Carefully remove the tree, trim any circling roots, and place it in fresh potting mix.
Propagation
Propagation can be achieved through seeds or cuttings.
For seeds, collect them in late summer, stratify for 30 days, and plant in spring. For cuttings, take 6-inch stem cuttings in late spring, dip in rooting hormone, and plant in a moist potting mix. Keep them in a warm, humid environment until roots develop.
When it's unhappy
Leaf scorch
Why it happens
High temperatures and low humidity can lead to leaf scorch.
How to fix it
Ensure adequate watering during dry spells and consider increasing humidity around the tree.
Powdery mildew
Why it happens
High humidity and poor air circulation can cause powdery mildew.
How to fix it
Improve air circulation by pruning and avoid overhead watering. Use fungicides if necessary.
Root rot
Why it happens
Over-watering or poorly draining soil can lead to root rot.
How to fix it
Ensure proper drainage and reduce watering frequency if root rot is suspected.
Bark peeling
Why it happens
Extreme temperature fluctuations can cause bark to peel.
How to fix it
Protect young trees from harsh conditions and provide mulch to stabilize soil temperature.
Insect infestations
Why it happens
Acer rubrum can attract aphids and scale insects.
How to fix it
Regularly inspect the tree and treat infestations with insecticidal soap or neem oil.
Care through the year
Spring
In spring, focus on fertilizing your Red Maple as new growth begins. Water regularly to keep the soil moist and monitor for pests.
Summer
During summer, ensure consistent watering, especially during dry spells. Mulch around the base to retain moisture and regulate soil temperature.
Fall
In fall, enjoy the vibrant foliage and prepare for winter by reducing watering. Prune any dead or damaged branches to maintain tree health.
Winter
In winter, protect young trees from harsh winds and extreme cold. Consider wrapping the trunk with burlap to prevent damage from freezing temperatures.
Toxicity & Safety
Acer rubrum is non-toxic to pets and children. No parts of the tree are considered harmful, making it a safe choice for gardens where children or pets play.
Good to know
Why are my Red Maple leaves turning yellow?
Yellowing leaves on Acer rubrum can indicate over-watering or nutrient deficiency. Ensure the soil is well-draining and consider fertilizing if needed.
How often should I water my Swamp Maple?
Water your Swamp Maple deeply once a week, or more frequently during hot, dry periods. Always check the top 1-2 inches of soil for moisture before watering.
What is the best soil for Red Maple trees?
Acer rubrum prefers well-draining, loamy soil with a pH of 5.0 to 7.0. Adding organic matter can improve soil quality and drainage.
When is the best time to prune my Red Maple?
The best time to prune your Red Maple is in late winter or early spring before new growth begins. This helps to shape the tree and remove any dead branches.
How fast does a Red Maple grow?
Acer rubrum has a moderate growth rate, typically reaching 40-60 feet tall and 30-40 feet wide at maturity. It can grow up to 2-3 feet per year under optimal conditions.
Is Red Maple toxic to pets?
No, Acer rubrum is non-toxic to pets and children, making it a safe choice for family gardens.
What are the signs of root rot in Red Maple?
Signs of root rot include yellowing leaves, wilting, and a foul smell from the soil. Ensure proper drainage and adjust watering habits to prevent this issue.
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