Georgia Gardener Newsletter Design Tip: September 18, 2008

The Genus Acer (Maples)

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We are rapidly approaching the fall foliage season when deciduous trees will begin to display spectacular colors from bright yellow to orange to red. I'm hoping that the fall color will be intense and long-lasting this season. Maples, both native and non-native, contribute a wide range of colors to the fall spectrum.

Even during the rest of the year, maples contribute greatly to the beauty of the landscape. Our native red (Acer rubrum) and silver (Acer saccharinum) maples and their cultivars and hybrids make up the bulk of the maple shade trees offered in the nursery trade. Both are fast growing, tolerate a wide range of growing conditions and offer good fall color with the red maples being predominantly red and orange while the silver maple is yellow.

Silver Maple Red Maple

Of course the red and silver maples aren't the only native maples to be found in Georgia. Lesser known native maples include the southern sugar maple (Acer barbatum), chalk maple (Acer leucoderme), the mountain maple (Acer spicatum) and the boxelder maple (Acer negundo) with its poison ivy-like leaves as well as several others.

Mountain Maple Boxelder Maple

The landscape value of some of our lesser known maples is too often overlooked. While the mountain maple and its similar cousin the striped maple (Acer pensylvanicum) really only grow well in the north Georgia mountains, the chalk maple and southern sugar maple are drought and heat tolerant smaller trees (20-30 feet) better suited to landscapes where the red and silver maples may be too large.

Japanese Maples (Acer palmatum)

Despite the fact that I'm known for my eager promotion of native plants, I must profess a real love for Japanese maples. There are so many different cultivars that I would never attempt a thorough discussion of them all. One group that really attracts my attention is the threadleaf or dissectum variety (Acer palmatum var. dissectum) of which there are literally dozens of cultivars. These Japanese maples are noted for their finely dissected fern-like leaves and come in a variety of colors from green to orange to red. They tend to be shorter, fatter and possess a weeping habit which makes them attractive even in the winter.

Red Dissectum Japanese Maple Green Dissectum Japanese Maple

The Japanese Maples available in this country are much smaller than our native red and silver maples which are mostly used as shade trees. The smaller stature of Japanese maples makes them suitable for small gardens, as focal points or even in containers.

Siting and Planting Maples

Fall is the best time to plant trees and shrubs. The soil is still warm enough to allow for some root growth yet the air temperatures are cooler and thus less stressful to new plants. I recommend the planting of trees and shrubs between the middle of September and the middle of February. Planting trees and shrubs as we get to spring doesn't give the plants enough time to settle into their new location before the heat of summer hits them.

When choosing trees, I tend to stay away from those that are balled in burlap. Sometimes these trees suffer root damage and have the trunk flare covered with too much dirt when they are dug and wrapped. Container grown trees usually do not have these problems. Examine the tree before purchase to make sure it has healthy roots, isn't pot-bound and that the trunk doesn't have any cracks (a problem with some maples that have been laid on their sides in the sun).

If you are planting one of the larger shade maples (red or silver), there are some things you need to remember. These trees can grow large (50-60 feet tall and wide), they cast dense shade and have shallow roots that can extend beyond the branches. If planted too closely (within 30-40 feet) to driveways and foundations, their roots can become a problem. Therefore make sure these trees have ample branch and root room to grow. On the other hand, Japanese maples do not seem to exhibit these surface root problems. Also unlike their American cousins, Japanese maples usually do better if planted where they are protected from the hot afternoon sun. This especially applies to the dissectum cultivars.

Always dig a wide hole for your trees. The best planting practices are to loosen (and perhaps lightly amend) an area that is 10 times the diameter of the root ball. Your planting hole within this area should be a minimum of 3 times the size of the root ball. Do not add soil amendments directly to the planting hole. This discourages the roots from growing out into the surrounding native soil. Always plant the tree at or a little higher than the depth at which it's growing. The flare that occurs where the trunk meets the roots should be visible. The soil needs to be loose, high in organic matter and well-drained although red maples can tolerate slowly draining soil. Apply and maintain a 2-3 inch layer of organic mulch over the root zone. Water the trees deeply once a week when allowed by the current watering restrictions. During the growing season, I recommend 15 gallons of water per week per inch of trunk diameter (measured at ~4 feet from the ground). An inch of water or rain over the entire area will achieve the same results. Once established, maples are pretty drought resistant.

Non-Native Invasive Maples

Unfortunately, we have several species of non-native maples that have become a problem. The Norway Maple (Acer platanoides) which doesn't tolerate the heat in most of Georgia is an extremely invasive pest plant in the Appalachians from northern Georgia to Maine, in the upper midwest and Pacific northwest. It is rapidly outcompeting other native trees. The Chinese amur maple (Acer ginnala) and the European sycamore maple (Acer pseudoplatanus) are also showing invasive behavior.

Because we have plenty of native maples and the well-behaved Japanese species, I think it best to not use the invasive maples listed above.

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