Japanese maple, superb foliage

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Delicate, deeply shaped leaves that turn fiery orange-red from the end of summer make Japanese maple (Acer) one of the finest shrubs for a pot or a sheltered corner. It comes from the underbrush of Japanese forests, and repays acidic, well-drained soil in part shade with a true festival of colours.

Planting japanese maple

Japanese Maple is planted in fall, but can also be planted in spring when purchased in a container.

• Japanese maple likes places that are partly shaded.
• Exposure in too much full sun could burn its leaves.
• Japanese maple despises chalky or limestone soil.
• It also shuns drafty locations that are subject to strong winds.

How to plant a Japanese maple

• Dig a hole 3 to 4 times as big as the soil clump.
• Provide a blend of one part planting soil mix and one part heath.
• Place the clump at the bottom of the hole.
• Backfill with the blend without burying the base of the trunk.

Potted Japanese maple

Growing Japanese maple in pots is more than just perfectly possible: this is an ideal shrub for the purpose.

• Use a good-sized pot.
• Check that the bottom of the pot has a hole in it (never use a pot that retains water).
• Pour a bed of clay beads or gravel at the bottom of the pot to form a layer 1 to 1½ inches (3 to 4 cm) thick to ensure proper drainage.
• Fill the pot with a blend of one part planting soil mix and one part heath.

Both in pots and in the ground, support the tree’s growth with mulch at the base of the tree to retain soil moisture.

Caring for Japanese maple

If properly settled in and with proper growing conditions, Japanese maple is easy to care for.

The most common mistake we’re aware of is about watering.

How to water Japanese maple

• Keep the soil moist in summer while avoiding excessive watering.
• Potted Japanese maple must be watered as soon as the surface soil is dry.
• The slightest lack of water might burn the the leaves.
• In case of elevated temperatures, misting the foliage in the evening helps cool the Japanese maple off.

• Where possible, water Japanese maples with rainwater, as hard tap water can gradually raise pH in pots and beds; although these maples tolerate near-neutral soil, strongly alkaline conditions can eventually cause interveinal yellowing.
• Water early in the morning or after sunset rather than in full midday heat, so less moisture evaporates before reaching the roots; the idea that droplets act as lenses and scorch foliage is a myth.
• Repot a container-grown Japanese maple every two to three years into a slightly larger pot with fresh mix, since rootbound plants hold less water and are more prone to drought stress and leaf scorch.

Pruning Japanese maple

It isn’t really recommended to prune it.

Your Japanese maple doesn’t like pruning, and only the oldest specimens will need some trimming to remain small.

If pruning must be done, then perform it in winter, whenever the weather isn’t freezing. Never prune anytime other than between late autumn and early spring.

• Start with properly disinfecting your pruning equipment.
• Eliminate old wood and dead branches.
• Apply pruning paste to avoid all risk of disease.

• Cut back to a bud or to the branch collar without leaving a stub, because Japanese maple seals its wounds slowly and dead stubs are an easy entry point for dieback.
• Prefer thinning out crossing or rubbing branches to shortening the branch tips, since heading cuts destroy the airy layered silhouette and trigger a thicket of upright regrowth.
• On grafted cultivars, rub off or cut away any shoot arising below the graft union, since these come from the rootstock and, being vigorous, can outgrow and crowd out the grafted variety.
• Remove unwanted branches while they are still thin rather than waiting, because large trunk wounds on a maple take much longer to close and give decay organisms more time to become established.

Diseases and parasites of Japanese maple

Japanese maple is a favorite host of aphids. Those little green or black bugs can colonize leaves and weaken your tree.

• Here is how to effectively fight off aphids

If you notice that some Japanese maple branches turn black, cut them off at the base and destroy them.

Indeed, many maple trees are infected by a disease called Verticillium which is a fungus capable of devastating an entire tree within months.

As soon as you see the disease on your tree, burn the dry branches. If the spots are only on the leaves, it may not be the same disease (black spots on leaves are harmless).

• Here is more on eliminating black spots on maple

Japanese maple troubles at a glance

Most setbacks on a Japanese maple show first on the leaves or the branches. Here is how to tell them apart and what each one calls for.

Settled in the right spot, with the right soil and sensible watering, Japanese maple is easy to care for.

Learn more about Japanese maple

Among the maples grouped under this name, ‘Osakazuki’, ‘Inaba-shidare’ and ‘Aconitifolium’ are all grown for the fiery hued foliage that begins its festival of colours at the end of summer, and each takes happily to a good-sized pot in part shade.

As its name shows, this maple is native to Japan. Indeed, it comes from the underbrush of Japanese forests. Even though they’re in the same family as common maple, they can’t cross-pollinate because they’re too far apart genetically.

It has fiery hued foliage in fall, and a true festival of colors starts at the end of summer.

It’s common practice to group together under the title “Japanese maple”, all types of maple coming from that country. Included are Acer japonicum, Acer shirasawanum and Acer palmatum.