Bigger is not always better. Just ask all of the folks who go out of their way at the nursery to purchase dwarf trees. In small-yard design, these mighty mites naturally stand head and shoulders above their taller counterparts as the right choice for the allotted space.
The fact is that many homeowners new to the constraints of small-yard design make the mistake of planting a specimen that is too big for their landscapes. The result of their poor selection is that the plant quickly outgrows its space, necessitating its removal after only a short period of time in the ground. Learning from their mistake (hopefully), they make a wise choice next time around and purchase a more appropriately sized specimen.
Evergreen Dwarf Trees
If a plant is characterized as a "pine" yet is used as a ground cover, that gives you a pretty good idea that it is a dwarf tree. Such is the case with some types of mugo pines: These evergreens (3 to 5 feet tall x 10 feet wide) have a broad-spreading habit that makes them a popular choice as a ground cover.
Dwarf Alberta Spruce
If you are a plant novice, you may see dwarf Alberta spruces around all the time without even knowing it. You will often see them used in balanced pairs, flanking a front entrance. Because they will remain relatively small for a number of years, people sometimes treat them as container plants for the porch.
But beware: As a plant that may eventually reach 12 feet in height, Alberta spruce does not stay quite as small as you might like. "Dwarf trees" is, after all, a somewhat relative term. To keep the plant "in bounds," though, you can always prune it. The fact that the plant is a slow grower is another point in its favor if you landscape in a small yard.
Japanese White Pines
Some of the smaller members of the pine world have a message for you: Beware of the "guilt by association" pitfall in judging them. Any bad press you may have heard about the larger specimens, such as eastern white pines, Pinus strobus (their messiness, the tendency of their limbs to break, and more), should not influence your attitude toward the dwarf trees that happen to be pines.
One elegant example is Arnold Arboretum Dwarf Japanese white pine. At 10 years old, it will stand 3 feet tall, with a spread of under 2 feet.
Slender Hinoki cypress is an intermediate-sized Hinoki cypress, being more compact (about 15 feet tall, at maturity, and about 5 feet wide) than the species plant (which reaches more than 50 feet in height) but not as short as 'Nana Gracilis'. which stands at 9 feet tall at maturity.
Deciduous Dwarf Trees
Contorted hazelnut also goes by such common names as "Harry Lauder's Walking Stick" and "Corkscrew Filbert." Although technically a shrub, it can be cited as an example of a deciduous dwarf tree because that is how many people view it. Contorted hazelnut may actually be at its best in winter: Without any leaves in the way, you can better appreciate the madcap twists and turns of its branches. Its mature size is 8 to 10 feet in height, with a similar spread.
Small Japanese Maples
You may be most familiar with regular-sized Japanese maples, but there are also dwarf types that are useful for small-yard landscaping. For instance, Sharp's Pygmy Japanese maple (Acer palmatum 'Sharp's Pygmy') is said to reach a height of just 3 feet in 10 to 15 years. This plant bears green, deeply dissected leaves in summer that morph into a brilliant red in autumn. Perhaps better-known is that graceful weeper, the Crimson Queen Japanese maple (8 to 10 feet tall x 10 to 12 feet wide).
Weeping Pussy Willows
Perhaps you've gone out into the woods on a late winter's day to cut some branches from a pussy willow tree (or shrub) to bring them home, place them in a vase, and admire them whenever you need a reminder that spring will, eventually, return. If so, you probably know the pussy willow as a rather wild-looking plant, interesting for its catkins but perhaps not shapely enough to grow in the landscape.
But there is a type sold at nurseries that has a nice, weeping form, making it suitable even for the landscapes of people who like their plants tame-looking. It reaches 6 to 7 feet tall, with a spread of 5 to 6 feet.
Tiger Eyes Sumac
Like contorted hazelnut, sumac is, technically, classified as a shrub, even though its trunk is tree-like. But, given the beauty of Tiger Eyes, it is doubtful that you will want to quibble over technicalities. A yellowish-lime color for most of the growing season, the foliage goes berserk in fall, morphing into a mix of yellow (usually the predominant color), orange, and red. At most, it will reach 6 feet tall and 6 feet wide.