Smaller trees, like dogwoods, require less space and have beautiful springtime blooms.
Small trees have skyrocketed in popularity, mostly thanks to utility companies. Trees no taller than 25-35 feet will not grow up into overhead power lines, which reduces tree-related outages and the need for heavy pruning to achieve clearance.
Smaller trees require less space above and below ground than larger trees do, which generally (but not always) results in fewer and less severe conflicts with infrastructure. Highly urbanized planting sites are often too cramped for large trees, whereas small trees can more easily be tucked into tight spaces.
Small trees are no less prone to storm damage than larger trees. Yet, shorter trees with small diameter wood are inherently less likely to cause serious harm when they break.
In spring, dogwoods, crabapples, cherries and other small trees push prolific, show-stopping blooms that few shade trees can match.
In spite of these benefits, however, there are some serious shortcomings to small trees.
Thanks to ecological adaptations in their native environments, small trees may have short but very wide canopies, multiple stems or trunks, low branching, and irregularly shaped crowns.
These growth forms are generally not appropriate along streets, in parking lots or in commercial districts.
Can you imagine a vine maple in a sidewalk cut out or a parking lot island? You would constantly be hacking up the tree to provide the clearance and visibility you need in those settings.
Small trees are perhaps the worst trees to plant for sign visibility. Pruning up the low branches almost never achieves good line-of-sight with signage, and cutting off the top of the tree – topping – damages the tree and can lead to many tree health problems.
Many small trees, including Cherries, Plums, Pears, Crabapples, Hawthorns and Serviceberries, are susceptible to a battery of insect and disease problems, which can reduce tree health, increase mortality and drive up maintenance costs. Some orchardists are concerned that pests and diseases harbored by ornamentals may inadvertently threaten local fruit crops as well.
Environmentally, small trees are dwarfed by larger ones. A small tree casts less shade, buffers fewer winds and conserves less energy. Small trees also intercept less stormwater, scrub fewer particulates from the air, and capture less carbon than large trees will. The relatively shorter lifespans of most small trees means what benefits they do provide won’t last as long.
A small tree is beautiful in bloom, however, few small trees can achieve such architectural feats as framing and softening the visual appearance of large buildings, delivering the much-coveted tunnel-effect on tree-lined streets or providing a more comfortable sense of human scale in pedestrian areas.
Sometimes a small tree is the best option, such as when power lines are overhead, but small trees aren’t a panacea. Planting the right tree in the right place should always include an analysis of the pros and the cons. And in fact, knowing the cons may be more valuable.
This article was first published on “Ear to the Ground,” the official blog of the Washington state Department of Natural Resources. For more information on tree care, go to dnr.wa.gov/urbanforestry.
