Some of the most spectacular trees in the garden are from the Acer palmatum family – Japanese Maples. Some varieties have vivid spring foliage while others are more striking during the fall or winter. Some have yellow leaves, others have green leaves and still others have various shades of pink, red or purple leaves. Fall colors vary from yellow to orange to red. Starting in the early 1600’s many Japanese gardeners started cultivating and breeding Japanese Maples.
There are more than 300 different varieties or cultivars available today, ranging in size from 2′ tall mature trees, to 35′ tall by 40′ wide Japanese maples.
The biggest challenge in using Japanese maples in the garden is choosing the one you like the best because there are so many types, colors, shapes, and rates of growth from which to choose.
How to Plant Japanese Maple Trees
The ideal soil for Japanese maples is sandy soil with plenty of organic matter in the soil. However, Japanese Maples will grow in almost any soil condition as long as the soil does not stay soggy wet. The better the soil conditions are, the better Japanese Maples can withstand other poor growing conditions, such as wind, water-related problems, heat stress, insect pests, and diseases.
Prepare your soil properly before you plant and you will not have as many problems in the future. Dig your hole at least twice as large as the rootball. Mix 20% to 30% Acid Planting Mix with the soil you remove from the hole, along with one cup of Dr. Earth Starter Fertilizer. This fertilizer contains Mycorrhizae and other beneficial bacteria that really help Japanese maples flourish in your soil. Don’t plant your Japanese maple too deep. Keep the graft at ground level, or a little above the ground. It is better to plant your tree too shallow than too deep.
Fertilize your new tree every two weeks for the first two months with Root Starter. Water your tree every day the first week. Make sure that you water it with a hose and not just let the sprinklers water it for you. After the first week, water your tree a least once a week with a hose. Give it 5 to 10 gallons of water each time you water, not just a cup or two. Again, don’t rely on sprinklers to water your tree the first summer.
Fertilizer and Soil pH Requirements
Japanese maples will grow in almost any soil pH but they prefer a soil with a slightly acid pH. Unfortunately we do not have acid soil conditions in Utah so you will need to make your soil more acidic. At planting time you can amend your soil with Acid Planting Mix to give your tree a quick start. After the first year you will need to apply sulfur, every spring, around the dripline of your tree to help keep the soil acidic.
High alkaline soil conditions prevent the roots from absorb- ing nutrients and water quickly enough to satisfy their needs, so the trees often show signs of leaf scorch even when the soil is kept moist. High alkaline soil conditions prevent Japanese maples from surviving in some conditions that the tree would otherwise tolerate such as ‘full sun’ areas, windy areas, or wet areas.
Japanese maples do not need a lot of fertilizer. In fact, too much fertilizer stimu-
lates too much growth and makes the tree more ‘leggy’ and weak. Fertilize Japanese maples once a year, in the early spring, with the same type of fertilizer that you use for rhododendrons, azaleas or other acid-loving plants. A monthly application of a soluble, acid-type fertilizer, from May through August, will also help keep the roots growing strong. Do not apply any liquid fertilizers directly to the leaves, it will burn them. Japanese maples flourish in the same growing conditions as Rhododendrons and Azaleas.
Water & Wind
Watering Japanese Maples
Japanese maples do not have any particular, or special water requirements, other than consistency. They can survive on limited water or with plentiful water, just as long as it is applied consis- tently. Do not give the trees a lot of water for a while and then drastically reduce the amount of water. The trees may struggle and the leaves may either dry up or burn. The opposite is also true, do not give the trees limited water and then dramatically increase the water. You may stimulate unwanted growth at the wrong time of year.
Water Japanese maples regularly, especially during the hot, windy weather of July and August. Do not sprinkle the leaves, or the water may actually burn the leaves instead of helping to prevent summer leaf scorch. Proper water management is one key to successful results when growing Japanese maples.
Preparing for Wind
Japanese maple trees hate hot, dry winds. South winds are the worst. There is not much you can do to prevent damage from these south winds during July and August so keep your tree as healthy as possible. The best prevention for this leaf scorch is to water your trees during, or immediately following, a hot wind. This extra water may help minimize any leaf damage. Remember to keep the water off the leaves during these hot, windy periods.
Japanese Maples are very hardy. They can tolerate most winter temperatures when they are healthy. Most Japanese maples that die during the winter either die from root rot, or from the soil drying out too much during the late-fall or winter. Root rot is a soil disease that usually starts by keeping the soil too wet, for too long of a time period during the spring and summer. Many gardeners kill their Japanese maples with kindness.
More Japanese maples die from the hot-dry summer weather conditions than die from the cold winter weather. One factor to remember is that it can be 15 to 25 degrees hotter right next to a house than it is out in the middle of the lawn or garden. This temperature variation can be just enough of a factor that the tree will not survive in that sunny condition, right next to the house, but it will grow just fine in a sunny area out in the yard. The same is true for trees planted next to white vinyl fences.
Placement of Japanese Maples
Most Japanese Maples prefer morning sun with some light afternoon shade. However, Japanese maples can grow almost anywhere in the yard. They will tolerate full sun, partial sun, or a lot of shade. The longer the tree has been planted in the yard, the more stress the plant can tolerate. A newly planted Japanese maple may struggle the first summer or two in the full sun. As the roots become established in good soil conditions, and the tree is watered and fertilized properly, the tree will grow just fine in most any area of your yard, including the hot, sunny areas. Green-leaf Japanese Maples tolerate the hot, sunny areas the best but many of the ‘larger-leaf’, red-leaf Japanese Maples will also tolerate the sun. The smaller laceleaf Japanese Maples will struggle in the hottest areas of the yard.
One factor to consider when you place your red Japanese maple is that they do need a little sunlight to maintain their brightest-red color. Too much shade minimizes the red shades. The leaves will not be as striking in the shade as they would be if the tree was planted in another area with more sunlight. Leaves tend to be greenish-red or a bronze color in the shade.
Prune Japanese Maples as little as possible. Do major pruning just before the leaves emerge in the spring. Japanese Maples do not respond well to major pruning. They do not send out new leaves or branches on the old wood. Be sure that you make all major pruning cuts just above another side branch that already has plenty of smaller twigs.
Minor corrective pruning and shaping can be done all sum- mer. The only regularly pruning that might need attention is to remove any excessive ‘twiggy’ growth that makes the tree too dense, especially when it is young.
Japanese Maples are relatively trouble-free. The biggest disease problem is from the root rot diseases; pythium, verticillium or fusarium. Keeping your tree healthy is the best way to prevent root rot. Adding sulfur to the soil each spring also helps prevent many root diseases from becoming a problem. Keep your soil consistently moist and not constantly wet.
Aphids, spider mites, and beetle or moth larvae can be an occasional pest that may need to be controlled once in a while. If all plants had as few pests as the Japanese Maples, gardening would be much simpler.
Growing Japanese Maples in Containers
In many areas Japanese Maples are used extensively in containers on the porch or patio. In our climate they do not survive without some major winter protection. Many Japanese maple roots die if the soil temperature drops below 14 degrees F. If you can protect your Japa- nese maple, in its container, from getting below 14 degrees F., you can usually have Japanese maple trees grow and flourish in pots on your patio. You may have to move the pots into an unheated shed, put them next to the house, bury them in straw, or make a structure to hold straw around them during the winter. This straw may help to keep them above the critical temperature.
Another important part of winter protection is water. Do not let the container completely dry out during the winter months. Water it when it starts to dry out. The best way to water plants during the winter is with snow. As the snow melts just give the container another shovelful of it.