Maples (Acer spp.) are normally single-trunked deciduous shrubs to large trees. They are commonly grown as shade trees, and frequently produce red, yellow or orange fall colors. The canopies may range from narrow and columnar to large and wide. Sizes can range from about 8 feet to 100 feet tall. Maples sold as clumps are either one tree with three or more trunks -- sometimes called multi-trunked trees -- or three trees planted together in the same pot or hole. While maples aren't often planted in clumps, a few types are sold as both single-trunked trees and clump forms.
Vine maples (Acer circinatum), thriving in U.S. Department of Agriculture plant hardiness zones 4 through 8, are probably sold as clumps or multi-trunked trees more often than as single-trunked trees. Sometimes they are grown that way in the nursery, but often they are collected in the wild where they grow naturally as clumps. Permits are required to remove trees from forests. Vine maples are native to the Pacific Northwest, and several varieties are available, such as "Pacific Fire" (Acer circinatum "Pacific Fire") with red bark, and "Pacific Purple" (Acer circinatum "Pacific Purple") with purple leaves.
Probably the most notable feature of the paperbark maples is the shiny, cinnamon-colored exfoliating bark. Because the bark is so remarkable, this tree holds interest year-round. In fall, the foliage turns a bright crimson. They are normally small trees reaching 18 feet in the landscape, but can reach 50 feet tall with age. Paperbark maples are hardy in USDA zones 5 through 8. They are usually sold as single-trunked trees, but can often be found in a clump-form.
Amur Maples (Acer ginnala) are small trees that reach about 15 feet tall. Amur maples and their cultivars are hardy in USDA zones 3 through 8 and are known for their cold hardiness. They are small trees that reach about 20 feet tall and wide, and the leaves display red, orange and yellow fall colors. They can be found as both single-trunked trees and clumps. A couple of varieties are available, including "Compactum" (Acer ginnala "Compactum"), which grows to only 8 feet tall and wide, or "Flame" (Acer ginnala "Flame"), with flame-red fall colors.
Hedge maples (Acer campestre) are also called cork bark maples because the branches are covered with a corky bark. They are sold both as single-trunked trees and as clumps. Amur maples and their cultivars are hardy in USDA zones 5 through 8. They can reach 35 feet in height and width with age, and while most maples display colorful fall foliage, Amur maples bear yellow fall foliage. Several varieties are available, including "Compactum" (Acer campestre "Compactum"), a globe-shaped dwarf, and "Carnival" (Acer campestre "Carnival"), a variegated form.