Cedar Rim Nursery

Acer palmatum dissectum

Japanese Maples – ‘King of the Garden’
Japanese maples make up one of the largest and most intriguing groups of landscape trees to date. The Japanese maple is useful as a specimen throughout each of the 4 seasons as well as an excellent choice for any small garden, large container, or bonsai subject. No other tree offers such varied colours, shapes, and textures in leaves and bark as well as sizes, shapes, and uses. And while each member or this family is truly unique, each also presents a similar characteristic: they each add elegant beauty and airy grace to any setting.

The Japanese maple, or Acer palmatum, belongs to the family Aceraceae and includes more than 250 cultivars to date. As a group, Japanese maples display round-headed forms with simple, opposite leaves and 5 – 9 shallow to deep lobes in sizes ranging from 2 – 5 inches (5-13 cm). The leaf colours range from mid green to red, burgundy, golden, and variegated with fall shades of brilliant reds, yellows, and oranges. Their flowers are small, purple-red pendulous corymbs, appear in spring, and are followed by red-winged fruit in late summer. Their average mature height is approximately twenty-five feet with a span of thirty feet for non-grafted specimens. Their shapes range from tall trees or large, multi-stemmed shrubs to low growing, mounding cultivars. They originate from China, Korea, and Japan and were first introduced into England in 1820 and available in the U.S. from a California nursery in 1854.

Cultural Maintenance:
When choosing the site for a Japanese maple, be sure to select one that is sheltered from strong winds and severe afternoon heat. Most will respond well to a spot that receives full morning sun and some afternoon shade. A bright, north or east side of a house is usually ideal because it is sheltered from winds and the heat. A spot that receives intermittent shade from larger deciduous trees is also appropriate for hot areas on the south or west side of the house.

The ideal soil is a sandy loam and must be well draining and consistently moist without being overly wet. If clay is apparent, add compost, sand, and peat moss to lighten the soil or consider a raised bed situation to lift the tree’s roots and create a specimen site. Provide consistent watering throughout the growing season, especially with newly planted trees. Also remember to water in the morning or the early evening to avoid scorching the leaves in the summer midday sun. With this said, however, slow down on the watering in later summer to allow the trees to begin entering dormancy properly. Established Japanese maples will thrive without additional irrigation as long as they are properly mulched to maintain even soil moisture. The ultimate key to irrigation is uniformity rather than quantity, i.e. consistent, even watering rather than large amount few and far between.

Fertilizer requirements are not intense; one light feeding in spring prior to leaf emergence is adequate as they are not heavy feeders. A useful step is to mulch the trees with compost or bark mulch to protect the roots from winter freezing and hot, dry conditions in summer.

NOTE: if your Japanese maple is planted in a bed surrounded by annuals and perennials, do not fertilize after mid summer. Fertilizing these beds into the fall will continue to encourage new growth on the maple and will hinder the dormancy that should start to occur in mid summer. Failure to be properly dormant can cause die back and winter damage on the maple’s shoots that often does not appear until the following spring.

If a Japanese maple is to be transplanted, one must take as much of the root system as is physically possible. As well, the root ball must not be exposed to air or direct sunlight for any length of time. This will allow for less chance of transplant shock and possible loss of the tree. Dig the new hole slightly larger than the root ball and the tree should be set at the same level at which it was previously growing.

Pruning:
The pruning needs of Japanese maples consist of removing dead or damaged wood and any small crossed shoots in the fall and opening up the tree’s centre to allow for air circulation. Any pruning to shape should be done sparingly and in the late summer to early fall when the sap has slowed. This type of pruning should not be done in winter or early spring to prevent die back and/or infection of cut stems. Any major spring pruning can result in bleeding stems and possible infection.

Shaping of your Japanese maple should be done slowly and from the inside to the outside. Stand back and study the tree’s shape carefully and try to visualize the form before making the cut and removing the branch. These efforts will make themselves rewarded in the long run when you have a beautifully shaped tree form.

Planting new trees:
Japanese maples have a fibrous root system that will predominantly grow in the top layer of the soil. This allows for companion plants and shrubs to be planted nearby without the fear of competition from the maples. New trees can be planted in spring or fall. When planting in spring, be sure to water deeply at least twice a week and never let the Japanese maple dry out! It leaf tip burn occurs, the tree may be getting too much afternoon sun or not enough water or both. In extreme drought conditions, the maple may lose all of its leaves. This is the tree’s way of protecting itself against lack of water and new growth should start to appear within a few weeks time after a thorough soaking is given to the root zone.
When planting in the fall, try and plant at least 4 – 6 weeks before the ground freezes to allow for new feeder roots to develop and establish. This will also make for a better start to new growth in the spring. Be sure to water regularly and deeply until the ground freezes and the tree has become dormant. Many people forget that newly planted trees require a lot of water even in the fall until the winter rains begin. Mulching will also help with maintaining consistently moist soil at this time and will help to insulate the roots through the coming winter.

NOTE: when applying mulch, keep it a few inches away from the trunk to allow for proper air circulation.

In winter, remember to watch your Japanese maples and remove any snow accumulation as soon as possible to prevent branch breakage. Do not allow the branches to freeze to the ground as this will prevent the tree’s ability to move and branch cracking or breakage may be more prevalent.

Japanese Maples in Containers:
Many people choose to grow and display their Japanese maples in containers to allow for the best viewing in their landscapes. This is not difficult, but it does require some attention.

In containers, Japanese maples prefer full sun through the morning and open shade in the afternoons. Some may be grown in warmer sites as long as their roots are kept cool from the afternoon heat. Regular irrigation is essential for container grown maples to ensure beautiful foliage. With regard to soil, choose a well draining potting soil.

The container itself can be any well-constructed wooden box or frost proof decorative pot as long as there are several drainage holes. A container that is somewhat broader than it is high is suitable to provide proper stability. As the tree grows, the container’s size should be increased slowly every few years. NOTE: never plant a small tree into a large container. This will overwhelm the small root system and retard the tree’s growth. 1-year old trees require approximately 2 gallons of soil; 3-year old trees require about 5 gallons of soil. From this size, you may want to transplant to a patio container of about 15 gallons once the tree has outgrown the 5 gallons.

With regard to fertilizer, it is much more important than with trees in ground. A balanced fertilizer with complete micronutrients is best applied at the lowest recommended amount. A liquid feed such as Miracle-Gro can be applied from spring bud break until the end of July or a slow-release form such as Nutri-coat or Osmocote may be used. NOTE: Japanese maples do not require and will dislike a high nitrogen fertilizer.

Pruning of container grown Japanese maples is important since these trees will be viewed from a close position and their winter silhouettes are essential attributes. Light pruning or pinching can be done in spring to direct growth. Do not remove anything larger than a pencil. Any other pruning can be performed in late summer, early fall to limit growth or remove any lanky shoots.

Root pruning of containerized maples must be done every 3 – 5 years. Young trees need only have any long, circling roots removed, but larger, older trees should have any large, woody roots removed and/or remove the outside 2 – 6 inches of roots. Replace the tree within the same pot with new soil added to the bottom and sides. A liquid application of Transplanter at this time will help in encouraging the new root tips to grow.

It has been demonstrated that root damage can occur in container grown Japanese maples at –10°C so some attention must be given to winter care. If the container is too heavy to move and the tree must be protected during the winter months or during a cold snap, wrap the planter with a thin, poly-foam sheeting and then with several layers of burlap - this will safe guard against any root damage due to cold temperatures. Small containers can be set in beds of mulch or sawdust to provided insulation of the roots. The mulch must cover the top 2 – 5 inches of the container with the top of the tree exposed. This will allow the maples to survive temperatures of –18°C once they have properly entered dormancy.

Links