Maples are among the most popular garden trees and shrubs. Many species have very decorative leaves and display magnificent fall foliage for their season finale. We provide an overview of the genus.
The genus maple (Acer) includes more than 100 species worldwide, most of which are deciduous trees and shrubs that are native to temperate and tropical zones of the northern hemisphere. They belong to the soapberry family (Sapindaceae) and within this the subfamily Hippocastanaceae. Some particularly beautiful wild species have come to Europe from China, Japan, and North America. Species native to Central Europe include Norway maple (Acer platanoides), the stately sycamore maple (Acer pseudoplatanus) at heights of over 100 foot, and the field maple (Acer campestre). The Japanese maple (Acer palmatum), native to East Asia, is one of the smallest species.
Appearance and Growth
From delicate small shrub to a mighty large tree: The species and varieties of maple are diverse like almost no other genus of tree. Maples are easily recognized by their leaves, which are mostly palmate and lobed, and either simple or pinnate like the box elder (Acer negundo), i.e. composed of leaflets. The leaves of most maples have a bright yellow or red color in fall.
Most species flower in spring before the leaves appear, the flowers are relatively inconspicuous. But they can be more eye-catching in their entirety as luxuriant panicles, clusters, or corymbs. During the summer, the fertilized flowers produce small nut fruits, which are connected in pairs to long, dry-skinned winged appendages. The winged fruit fall off when ripe and spin through the air like tiny propellers. Thanks to this clever strategy, maples are able to carry the ripe seeds relatively far from the mother tree.
Besides beautiful bud coloring and fall foliage, the picturesque growth form and pretty bark patterns of some species are very ornamental. For example, the snake-bark maple (Acer capillipes) and grey snake-bark maple (Acer rufinerve) have decorative bark. The papery, shiny red-brown bark of the paperbark maple (Acer griseum) is highly ornamental. Our gardens are home to around 30 different species of maple and a number of cultivars. There are numerous varieties of the Japanese maple, in particular, with highly variable leaf shapes and colors.
Location and Soil
Most maples are very frost-hardy and do not have any specific location requirements. However, it is often a good idea to choose a sheltered spot so that the beautiful fall foliage is not too exposed to the wind. The Japanese maple (Acer palmatum) and fullmoon maple (Acer japonicum) are particularly sensitive to wind. This species should not be planted in full-sun locations. When selecting a location, make sure that the maple is not exposed to late frosts and can enjoy the early morning sun. While the field maple thrives in calcareous soils, others grow almost anywhere, whether in heavy clay soils or acidic soils. In general, the soil should be nutrient-rich, permeable and retain moisture well. Locations within paved areas are unfavorable for maples, as the vast majority of species need open ground and do poorly in dry urban climates.
Maples can be purchased in stores as container plants, bare-rooted or with a root ball. First, find out how tall and wide the maple will grow over time, and check whether the intended location has suitable light, climate and soil conditions. It is advisable to plant the trees in spring or fall when the temperatures are relatively mild. And the rain can also get them off to a good start. Frost-sensitive species should only be planted out in the spring, if possible. Depending on the size of the tree, first, put one or more stable stakes into the planting hole. The hole should be two to four times as wide as the root ball. Use a garden fork to loosen the side wall and base so that the roots can spread more easily. Water the tree well and make sure it has plenty of water in the first two years, especially in dry conditions.
Maples tend to have a very shallow root system. You should never work the ground below the shrubs with a hoe, as this could damage the fine roots close to the surface. Using a layer of bark mulch as groundcover protects the roots from drying out and enriches the soil with humus. Young specimens in particular should be fertilized in spring with horn shavings or mature .
Maples do not need regular pruning. From time to time, very young plants might need a few adjustments for the crown to grow well. The trees should be pruned in summer, as they can flower very strongly in late winter and spring.
Overwintering or Winter Protection
The maples available from nurseries have no problem coping with the winters in these parts. Late frosts can be damaging to the new growth of some species, but they grow back without any issues. Japanese maples do not need any winter protection as container plants. Experience in Scandinavia has shown that they even sprout again when the root balls have completely frozen through in winter.
Where to plant
Large maple species, such as the Norway maple (Acer platanoides) and sycamore (Acer pseudoplatanus) are often planted as street and park trees. They are sometimes found in larger domestic gardens too. The ‘Atropurpureum’ and ‘Brilliantissimum’ varieties of sycamore are good for gardens. The Globe Norway Maple (Acer platanoides ‘Globosum’) is a very popular small-crowned garden tree. The native field maple (Acer campestre) is also used for trimmed hedges and is an important tree for wildlife gardens and landscapes that protect birds.
The smaller, more exotic species are mostly grown as solitary specimens, so that their picturesque crowns can develop uninterrupted. Slow-growing varieties of the Japanese maple are suitable as winter-hardy potted plants for balconies and patios. The mother species is also grown as a bonsai. Asian maples are generally a good choice for Japanese gardens.
To this day, the North American sugar maple (Acer saccharum) is of great commercial value, because the sap extracted from its bark is used for everyday maple syrup. In this country, the sycamore is an important forest tree – it provides exceptionally high-quality wood which is used for furniture building, among other things.
Important species and varieties
Asian maples offer picturesque growth and particularly beautiful fall foliage. In addition to the golden full moon maple (Acer shirasawanum ‘Aureum’), this includes varieties of the Japanese maple (Acer palmatum) and full moon maple (Acer japonicum). The full moon maple variety ‘Aconitifolium’ is widespread in this country with golden yellow, red, or dark red fall foliage. Red Cappadocian maple (Acer cappadocicum ‘Rubrum’) reveals a beautiful play of colors. New growth is violet-red, the leaves then turn green in summer, and shine a bright golden yellow in fall.
If you are looking for a maple with beautiful tree bark, try a grey snake-bark maple (Acer rufinerve) or snake-bark maple (Acer capillipes) which have long white stripes on their bark. The paperbark maple (Acer griseum) is another eye-catching species with mahogany to orange-colored bark that peels in thin layers. The Montpellier maple (Acer monspessulanum) is adorned with small distinctive leaves.
Maple species are generally propagated by seed. Some species even self-seed in the garden with their winged seeds. A number of different grafting methods are used for the propagation of cultivars, such as bud grafting and – for garden varieties of the Japanese maple – splice grafting in summer under glass. The Globe Norway Maple is cleft-grafted in spring or bud-grafted in summer onto the tall trunks of the Norway maple, because the variety grows slowly and does not form a straight trunk. Propagation by layering is also possible.
Diseases and Pests
Many species are susceptible to leaf diseases such as powdery mildew and tar spot. Choosing a species-appropriate location is one of the most important requirements for healthy trees. Maples are occasionally affected by pests such as aphids, spider mites, gall mites, and cicadas. Japanese maples in particular are easily infected with Verticillium wilt in heavy, damp soils. Symptoms of the fungal disease include pale leaves that wilt quickly, a cracked bark, and stems and branches that seem to dry out for no apparent reason. With a little luck, you can save the maple by cutting off the infected branches, sealing the cutting points with grafting wax, and planting the tree in a different spot in the garden or in a new tub. If a tree becomes infected with sooty bark disease, this must be reported to the local plant protection service and immediately felled, as the fungal spores can also be harmful to humans. The disease threatens the native sycamore in particular, but the Norway and field maple can also be affected.