Understory Trees: Small Trees With Big Payoff

By Cathy Jean Maloney
The Morton Arboretum

Make no big plans for your garden this spring.  Instead, consider small, understory trees for major impact.  

An understory tree fits neatly under the canopy of a forest or near a multi-story house.  Unlike large shade trees such as oaks or maples which can grow to 100 feet, an understory tree typically reaches maturity at fifteen to thirty feet.  It adds structure, texture, color and multi-season interest, and should be one of the first plants for your garden.  

“In today’s suburban or city yard, understory trees are really the answer,” says Peggy Pelkonen, The Morton Arboretum’s landscape architect.  She notes that while a typical quarter-acre lot can visually support just one large shade tree, many understory trees can be added for variety.  

“Understory trees may be very ornamental,” Pelkonen notes, “and their beauty is readily appreciated because you’re eye to eye with it.”

Redbuds (Cercis canadensis) are among Pelkonen’s favorites because of their exquisite purple-pink dainty buds in spring.  Shade-lovers, they are a good solution for many shadowy city lots or suburban yards with existing large trees.  Pelkonen likes the redbud’s heart-shaped leaves for texture in summer and bright yellow color in fall.  “The small, bean-shaped pods in winter are an added bonus,” she says.

Hawthorns (Crataegus) are another great small deciduous tree.  Their horizontal spreading branches are striking in winter, and most have tiny white flowers in spring, followed by colorful berries that birds love.  Pelkonen recommends ‘Winter King’ (Crataegus viridis ‘Winter King’) noting, “I really love that spreading shape, and it can handle urban situations.”

While many hawthorns should be planted away from heavily trafficked areas because of the thorns they drop, ‘Winter King’ is nearly thornless, according to Doris Taylor, Arboretum Plant Clinic manager.

In the dogwood family, Cornelian-cherry dogwood (Cornus mas) is covered with clusters of bright yellow flowers in spring, among the earliest to bloom.  It sports elongated, red fruit in late summer and has interesting peeling bark for winter interest.  Pagoda dogwood (Cornus alternifolia) is native to our region and features horizontal branching, flattened white flower heads in spring and blue-black berries that will have birds flocking to your yard.  The showy flowering dogwood (Cornus florida), while tempting, is very fickle in our region and rarely successful. “A good alternative is Kousa dogwood (Cornus kousa) which blooms two weeks later and is more tolerant of alkaline soils,” Taylor says.

Some trees look like multi-stemmed shrubs. Among Pelkonen’s favorites is a unique Peking lilac (Syringa pekinensis 'Morton' China Snow®) whose white flowers appear in mid-summer. “The flowers bloom much later than most lilacs, and the plant is very drought and salt tolerant,” Pelkonen says. She also favors spicebush (Lindera benzoin) with its dainty yellow flowers.

Serviceberry is usually seen as a tall, multi-stemmed shrub, but it may also be a small, single-trunk tree. As an added visual treat, lovely Cedar Waxwings may flock to this tree for its red berries.

Glad You Asked

Q.  I’d like to plant a crabapple, but don’t like their messy fruit.  Which one should I choose?
A. There are many new varieties of crabapples today with persistent fruit that don’t drop, such as ‘Donald Wyman,’ ‘Red Jewel,’ and ‘Sentinel.’  Some have great resistance to common crabapple diseases like scab, rust, and mildew.  See The Morton Arboretum website (www.mortonarb.org) for a complete list of crabapples suited to our area.

Q.  I want to plant an understory tree near the corner of my house.  How close can I plant it?
A. Understory trees work well to soften the edges of a house and tie it to the landscape.  While it depends upon the type of tree you plant, generally if you plant the trunk at least fifteen feet away, the tree and house will thrive.

At The Arboretum
It’s one of the most popular wintertime attractions: an unforgettable weekend of Siberian husky dogsled demonstrations, displays of huskies available for adoption, and presentations on the dogs’ history in “Tails On The Trails,” January 26-27, 11 a.m. – 4 p.m.

Cathy Jean Maloney writes for The Morton Arboretum.