Semi-dwarf trees, as the name implies, are intermediary between standard and dwarf trees. Most will grow within the 10- to 15-foot height range, and depending upon species, spread to that approximate width. In general, when deciding upon a variety to plant, look at what grows well as a standard form in your zone, and check for semi-dwarf cultivars of those. All of the trees listed here are carried by nurseries, online and paper catalogs. Natives can also be found through local native plant societies, conservation departments or botanical gardens.
Smoketree (Cotinus coggygria) is one of the more unusual of ornamental, flowering trees. It produces minuscule pinkish-purple flowers so numerous on the long panicles, that they form a smoke-like cloud, which seems to hover over the branches rather than being attached to them. It has a rounded, shrubby form and deeply textured bark resembling dragon scales.
The leaves are large and turn a kaleidoscope of color in autumn--often it is possible to find yellow, lime-green, purple, orange and deep red together on a single leaf. This spectacular native is at home on dry, rocky slopes in full sun, but adapts well to most growing conditions in zones 4 to 9.
An apple relative, the crabapple (Malus sp.) is a beautiful tree that with its over 1,000 known varieties offers at least one to be grown in almost any region. A few--notably Dago, Radiant, Thunderchild and Spring Snow--are hardy to elevations as high as 8,000 feet. Crabapples tolerate most soils, but like full sun or only the lightest shade. Fruits are both edible and ornamental, and the flowers range from white to a deep red-violet depending upon species variety.
The fringetree (Chionanthus virginicus) is a pretty native flowering tree growing well within semi-dwarf standards at only 12 feet average height (although it can, rarely, reach as much as 20 feet tall under ideal conditions). The fragrant, white strap-like flowers hang in heavy clusters, creating a thick "fringe" that almost covers the leaves over the entire tree in spring.
The fall foliage is also very attractive. It prefers sun to light shade in zones 3 to 9. This is a low-maintenance tree, native to rocky glades and adapted to drought conditions and very dry soil.
The flowering dogwood (Cornus florida) is a native species, attractive enough to be the official state tree of three states, and the state flower of two more. Most varieties are on the tall side with flat topped spreading habit, but the variegated (green and white leaved) cultivar, Cherokee Daybreak can be kept below 20 feet with judicious pruning.
Dogwood has the typical showy white dogwood flowers (actually the bracts), but continues its appeal throughout the autumn, with spectacular burgundy-colored leaves, and into winter, with ornamental fruits attractive to winter birds. It prefers a semi-shady location with some sandy to light clay soil, is drought-tolerant and will thrive even on well-drained slopes.
Cherry trees (Prunus sp.) are excellent choices for mid-zone regions (some extremes will grow in zones 4 to 9, but most do best in zones 6 to 8). The Japanese flowering cherries (Prunus serrulata) are among the loveliest of flowering trees, offering lush displays of pink or white blooms in the spring, though they can become rather tall.
The cultivar "Mt. Fugi" is a white and pale pink, semi-double-blooming variety with a manageable height of 15 feet. Cherries prefer full sun to partial shade and thrive in moist but well-drained soils.