Garden Care : Maples in Minnesota

Maples in Minnesota

New Englanders may think they have top bragging rights, but it would be hard to imagine Minnesota without all the beautiful maples that grace our landscapes. Here is a versatile group of plants that offer shade, size, shape and color. Except for one shrub-form maple, all the maples that live in our climate are trees. Amur maple can be grown as either a shrub or a small tree. Tree maples vary incredibly - from a compact 20 foot mature tree like the Sugar Cone maple to a towering 75+ footer - like the Majesty Sugar maple.

Although there are more than 150 species of maples found around the world, less than 15 species are native to North America. Maple trees are all botanically in the genus Acer. While they aren't grown for their flowers, all of them bloom early in the spring. Depending on the variety, some have separate male and female flowers and others have perfect flowers (with male and female parts in the same bloom). For homeowners, that means most maples will have seeds; a few are seedless and some have lots of seeds. The seeds on maples are called samaras. They are those flat papery pods with wings. A few other trees have similar winged seeds, but maple seeds are distinctive because they have paired wings. With the exception of boxelder maples, all the hardy maples have simple leaves that are lobed and coarsely toothed. The overall size and shape of the leaves vary greatly. Maples play several roles in the landscape. Most often, they are used to provide wonderful summer shade and fall color. They can also be used as a border tree, almost like a huge hedge, on large pieces of property. In the Twin City area, they are used extensively for boulevard plantings. They are also often used for their summer foliage color, their winter bark and their winter form. The amur maples have fragrant flowers.

When selecting the type of maple to plant, it is important to try to match the plant to the site. In the list below of the various maples suited to our area, any preferences as to site conditions are noted. This especially important if you have a particularly moist site, or the soil is heavy clay or sand. The mature height and width of the tree may also limit where it can be planted. And be sure to look at shape which varies from columnar through oval and round to broad. There are dozens of distinct varieties of maples well suited to landscapes in our area. While we enjoy having all these maples to choose from, there are, however, several very tempting varieties of maples that are not fully hardy in our climate, most notably, the Japanese, Korean and Seibold maples. These varieties are only hardy to Zone 5 and should only be considered if you have a warm micro-climate that is very protected. What is meant by soft maple or hard maple? And what difference does it make for the gardener? The terms apply to the strength and density of the wood they develop and, while some clearly fall into one category or the other, a few straddle that invisible line in between. Generally, sugar maples are the hardest maples. Close behind are black maples (often grouped with the sugars) and Norway maples. Silver maples are soft along with box elders. Red maples and a few others are in that middle zone.

For more information on all the hardy varieties of maples for our area, check out our information sheet entitled Maple Varieties. It will provide you with details about size, fall color, shape, site requirements and hardiness.

Care of Maples
Once established, maples are fairly easy to care for, but special care should be given to matching the maple to the site and following proper planting techniques. By matching the maple to the site, stresses are reduced that might lead to later problems. Whether you are planting a B&B, potted or bare root maple, It is crucial to make sure it is planted at the correct depth. To do this, find the area along the base of the trunk where it begins to widen and lateral roots start to spread outward. This is called the “root flare”. The root flare is the bottom of the trunk and the top of the root system. On a bare root plant, this will be easy to see. Ignore what might appear to be a soil line a few inches higher. On potted or B&B trees, the soil may be covering the root flare making it more difficult to identify. Gently remove soil along the base of the trunk until you find those first lateral roots. Unfortunately, B&B and potted trees sometimes are too deep in their soil for long-term growth. Once the root flare is identified, you can go ahead and plant the tree following directions, making sure the root flare is at or just above the surrounding soil level. Ongoing care of maples doesn't differ much from any other shade tree. They should be fertilized yearly when young and pruned as needed to encourage good branching structure. Maples can be pruned in the winter or in early summer. To avoid having to deal with maples seeping profusely, don't prune them in late winter or early spring. The seeping isn't usually harmful to the tree, but it can be stressful and draw a variety of creatures. That same sap is what is gathered for making maple syrup.

Problems
Maples can have problems with several types of insects and disease. Most of these problems affect the appearance of the maples more than they do the health. Being aware of possible problems lets the homeowner make informed choices as to treatments. In our area, maples are sometimes bothered by galls, aphids and cankerworms. The most common diseases that affect maples are anthracnose and verticillium wilt. There are also various cultural and environmental problems that may occur with maples. Most cultural problems are related to incorrectly siting the plant, planting the wrong variety of maple or planting too deep. Like almost every other shade three, maples also struggle with environmental stresses such as salt, exposure and pollution. Maples are also known for problems with the bark splitting during the winter.