How to Grow and Care for Osakazuki Japanese Maple

Japanese maples are known for their graceful twining branches, their longevity, their delicately-lobed leaves, and their brilliant seasonal color. The Osakazuki Japanese maple is a cultivar that 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. The cultivar was named after the shape of its cupped leaves. ‘Osakazuki’ means “a leaf like a wine cup” in Japanese. 

Because the Osakazuki maple grows to a maximum height of 20 to 25 feet tall and 10 to 15 feet wide and does well in partial or dappled shade, it makes 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.

Osakazuki Japanese Maple Care

Here are the main care requirements for growing Osakazuki Japanese maple:

• Plant it in a location where it gets a moderate amount of morning sun
• Make sure the soil is well-drained
• Keep the soil moist
• Don’t fertilize for the first two years after planting

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.

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.

Propagating Osakazuki Japanese Maple

Usually, Japanese maple cultivars like Osakazuki maple are propagated from grafts, which is an involved process and best left to horticultural professionals. However, after your tree is established, you might notice many tiny seedlings sprouting up around it. The seeds from a cultivar don’t produce plants that are true to the parent but if you don’t mind having an offspring that is different, you can dig those up and grow them in containers until they are large enough for planting in the landscape.

Potting and Repotting

Due it its size, Osakazuki is not a good candidate to grow in a container. Dwarf Japanese maple cultivars such as Acer palmatum 'Coonara Pygmy' are much better suited for growing in pots.

Overwintering

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.

Even if your location is within the zone range. Japanese maples need winter care to protect them from the harsh effects of wind, ice, and snow. Planting your Osakazuki maple in a protected location is the most important thing you can do to make sure it survives the winter.

Common Pests & Plant Diseases 

Japanese maples are unfortunately sought out by several pests, from Japanese beetles, which can defoliate a tree quickly, to aphids, mealybugs, scale insects, mites, and borers. If there are only a few insects, they can be washed off with a garden hose but for heavy infestations, you might have to use insecticidal soap or neem oil, or, as a last resort, non-organic synthetic pesticides.

The tree is also susceptible to cankers, verticillium wilt, leaf drop, powdery mildew, anthracnose, and sooty mold.

Common Problems with Osakazuki Japanese Maple

In addition to winter damage, a young Osakazuki tree maple is also prone to damage from 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.