Regional Gardening Reports :: National Gardening Association

In the Garden:
Pacific Northwest
February, 2009
Regional Report

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In spring and early summer, the leaves of the upright cultivar 'Oshio Beni' are an eye-catching light red. They fade to a reddish tan during a hot summer, but in the fall they turn an exceptionally beautiful, almost electric red.

Elegant Japanese Maples

It's easy to become passionate about Japanese maples. While most small trees are grown for their fleeting flowers, Japanese maples are grown for the beauty of their leaves which come in a great variety of shapes and colors. The leaves of the most familiar cultivars look like stars because they're divided into five to seven sharply pointed, serrated lobes. On some trees, the lobes in turn may be divided, to the point where the leaves take on a lovely feathery or lacy appearance. Leaf colors range from yellow-green to dark green and from bright red to deep blood red. There are also trees with variegated leaves that are green outlined with white or gold.

Japanese maples are beautiful in every season. In spring, the emerging new growth brings trees to life with a flush of fresh, light green or bright red color. In the heat of summer, the vibrant colors of spring may fade somewhat -- the greens deepen and the reds turn bronze -- but the unusual texture of the leaves continues to catch the eye.

Japanese maples thrive in moist but well-drained, slightly acidic soil in sun or part shade. Red-leaved cultivars need ample sunlight to develop their best color, but too much heat and dryness can cause the colors to fade. I've found the ideal site provides morning sun tempered by afternoon shade. Growing conditions in northern California and the Pacific Northwest, home of the largest Japanese maple nurseries in the country, are ideal. As a result, we have a huge variety of maples from which to choose.

Upright or Weepers
Almost all of the trees sold as Japanese maples are cultivars of just two species: Acer palmatum and Acer japonicum. A. palmatum is by far the most common, offering many varieties and forms and dozens upon dozens of cultivars. To make sense of it all, I divide them into two types: upright growers and weepers.

Upright trees tend to grow as tall as they are broad, typically reaching heights and spans of 15 to 30 feet. The leaves of upright trees generally resemble bold stars.

The second type of A. palmatum has a weeping habit. The branches arch downward, and the lower branches usually touch the ground. Growth is more horizontal than vertical: the span of a weeping tree is usually three or four times its height, so the canopy has a mounded appearance.

Weeping Japanese maples are slow growing. It may take 20 years for a tree to grow 5 to 10 feet tall. The leaves of weeping Japanese maples are deeply divided and divided again. Botanically, weeping Japanese maples belong to a variety of A. palmatum called dissectum, and so are often referred to as dissectums in catalogs.

The other common Japanese maple is A. japonicum. Japonicums differ from A. palmatum cultivars in the size and shape of the leaves. Japonicum leaves are larger (3 to 4 inches across compared to 1 to 3 inches for A. palmatum leaves), they have more lobes, and they have a more rounded shape.

Japonicums are large, upright trees, growing as tall as they are wide, often reaching 30 feet. Their leaves come in a variety of shades -- from palest green-gold to shiny dark green -- and in several different foliage forms -- from deeply divided to almost circular. Most are in their glory in the fall, when their leaves turn various shades of red, mahogany, orange and yellow -- often all at once -- making for an extraordinarily colorful display.

Selecting Cultivars
Because of their wide variety, Japanese maples can play many roles in the landscape. Upright growers make wonderful specimen trees in a lawn. The red-leaved upright cultivars stand out especially well against a backdrop of blue spruces or blue atlas cedars.

Because of their small size, weeping Japanese maples fit nicely into garden beds or containers. Their finely cut and colorful foliage makes them suitable companions for shrubs, perennials and ground covers. The red-leaved cultivars make wonderful accent plants in a border. Many flower colors, white and blue in particular, really shine against a red background.

Caring for a Japanese Maple
Given moist but well-drained soil and shaded from the heat of the afternoon sun, a Japanese maple requires little care. Its needs are similar to those of most other trees: occasional watering, fertilizing and pruning.

During long dry periods, give your Japanese maple a good soaking once a week. To reduce the need for watering, mulch the tree in a circle extending from the trunk to beyond the tips of the branches.

If growth is poor, I feed in spring or early summer, but never after the middle of August because fertilizer could encourage new, tender growth that won't have time to harden before the arrival of cold weather.

Upright-growing Japanese maples benefit from occasional pruning. Prune the inside branches to let in more light and reveal attractive twists in the trunk and large limbs. Prune the tips of the branches to shape the tree to your liking. The best time to prune is in winter when the trees are dormant.

Weeping Japanese maples rarely need pruning, but you can prune them back if they get too large for their space, or if they grow asymmetrically.

Whichever cultivar you choose to plant, you'll add a touch of elegance to your landscape with your new Japanese maple.

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