How to Grow and Care for Osakazuki Japanese Maple

Japanese maple tree in sun and shadow with green and orange leaves

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Japanese maples are known for their graceful twining branches, their longevity, their delicately-lobed leaves, and their brilliant seasonal color. The Osakazuki maple is notable for its thrilling range of seasonal color, beginning the spring season with bright green leaves that slowly turn olive green, then green tinged lightly with orange through summer. The orange leaves gradually become brighter, and finally the tree explodes in brilliant tones of deep vermilion and red in autumn. Like other Japanese maples, this cultivar provides a long season of dependable autumn color, making it a favorite for landscape plantings.

Because the Osakazuki cultivar grows to a maximum height of 25 feet, and do well in partial or dappled shade, they make a good choice for a smaller tree to plant beneath larger trees with high canopies, such as tulip poplars, oaks, large maples or catalpas.

This tree, if properly cared for, will provide many years of beauty in the landscape. Japanese maples are fairly slow-growing, so it's worthwhile getting a mature specimen if you can acquire one. The beauty and longevity of this tree are so desirable that many gardeners are willing to create the best possible growing conditions for them to keep them healthy and vibrant.

Botanical Name  Acer palmatum 'Osakazuki
Common Name   Japanese maple 'Osakazuki'
Plant Type  Deciduous tree
Mature Size   15-25 feet tall, 10-15 feet wide
Sun Exposure   Part sun to part shade
Soil Type  Well-drained, loam
Soil pH   Neutral, tolerates acidic soil
Bloom Time  Spring 
Flower Color   N/A, flowers inconspicuous
Hardiness Zones   5-8 (USDA)
Native Areas   Japan
Toxicity   Non-toxic to humans and animals
Bright red leaves on Japanese maple near blue-green evergreen tree

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Osakazuki Japanese Maple Care

Choosing a proper location is the most important step in growing an Osakazuki Japanese maple. First of all you must allow for this tree's size: up to 25 feet tall and wide! You will also want to make sure it doesn't get too much sun. Japanese maples are often planted as "understory" trees, receiving dappled light beneath the shade of taller trees. In a sunny location, try to plant so the tree receives morning sun instead of afternoon sun, as afternoon sun may prove too strong.

Light

The Osakazuki, like other Japanese maple trees, likes dappled shade, but also needs a small amount of sunlight to produce vibrant color in the leaves. Too much sun can be detrimental. Morning sun is better than afternoon sun, and protection from afternoon sun can help the tree thrive. For all these reasons, before planting, choose the location of your tree carefully to give it the best light conditions.

Soil

The Osakazuki Japanese maple is tolerant of acidic soils and so may make good companion plants for other shrubs that prefer an acidic soil environment, such as hollies, camellias, hydrangeas, azaleas, and evergreens. You'll want to make sure the soil is also well-drained and not heavy with clay, and the soil should be kept consistently moist but not wet, which is easier with a loamy soil mix.

Water

This tree prefers regular watering and if there is a shortage of rainfall, supplemental watering is desirable. Water deeply around the base of the tree at least once a week in hot dry weather. If the leaves show signs of crisping or wilting, lightly spraying the tree with a hose or sprinkler may be beneficial also.

Temperature and Humidity

The Osakazuki Japanese maple is suitable for USDA Growing Zones 5-8, and will likely not do well for long in 4 or below, or 9 or above. Mulch around the roots will help protect the tree from cold temperatures in winter, and of course help regulate moisture retention in the growing season. Being a deciduous tree, it can tolerate periods of dryness or humidity that are normal in temperate zones during the summer.

Fertilizer

This tree does benefit from some fertilizer, but it's important to know when and how to do this properly. Always take soil samples before fertilizing to know what kind of fertilizer to use and to avoid fertilizer burn. Wait until your tree has established itself, at least two years after planting. Experts agree the best time to fertilize is in late winter while the ground is still frozen; this way the fertilizer will be absorbed slowly as the ground thaws. You can also fertilize with a controlled release fertilizer in late spring, using pellets carefully inserted near the roots, and watering well.

Propagating Osakazuki Japanese Maple

Usually Japanese maples are propagated from grafts or seeds. In fact, you may notice many tiny seedlings sprouting up every spring after your tree is established. These can be dug up and grown in containers until they're large enough for planting, or moved to a location where winter winds won't kill them. It is also possible to propagate from softwood cuttings. Do this in summer, and use rooting hormone and potting medium. The basic steps for propagation from cuttings are covered here.

Pruning

Japanese maples generally benefit from as little pruning as possible. Dead or broken branches should be cut off, and branches that begin to cross one another should be carefully pruned to avoid crowding. The bark and flesh of the tree is sensitive, so be careful not to expose too much with cutting, especially in summer when hot sun can burn the tree. Early in its life, you can determine the shape of the trunk (either one single trunk or multiple ones) with pruning. Because the Osakzuki cultivar is so tall and upright, a singular trunk works well, but multiple trunks can look very dramatic, so it's really a matter of taste.

Common Problems with Osakazuki Japanese Maple

Strong winds in winter can damage these trees, so in addition to choosing a location with some wind protection, you may need to protect the tree before it reaches its full mature size. There are a few guidelines for protecting Japanese maple trees in winter gathered here. While your Osakazuki tree is young, also take care to protect it from a late spring frost (which is an increasing problem with unpredictable spring weather due to climate change). Another possible problem is damage to leaves in very hot dry weather; the leaves will feel "crispy" to the touch and perhaps turn pale or beige in color. Be sure to give the tree extra water at the base during heat waves or drought conditions, and remove any damaged leaves.

FAQ
  • Is Osakazuki Japanese maple taller than other Japanese maples?

    At a mature height of up to 25 feet, this is one of the taller varieties of Japanese maple, most of which are under 20 feet tall. Some dwarf varieties only grow to a maximum of 2 feet! The Osakazuki is an upright tree, unlike some Japanese maples that have a weeping or rounded habit, which also makes it appear taller.

  • How long does it take for the Osakazuki Japanese maple to reach its full height?

    These trees are considered slow-growing, adding between 12-24 inches of height per year. The Osakazuki will tend to reach its mature height within 10-15 years.

  • Is the Osakazuki Japanese maple okay to grow where the winter is harsh?

    Japanese maples are only hardy to Zone 5. They may survive in a Zone 4 if the winter weather is not too harsh, but usually they cannot tolerate the cold, ice and/or snow in Zone 4 or below for more than several years.