The Society of Municipal Arborists (SMA) SMA, comprised of urban forestry professionals worldwide, has chosen yellowwood (Cladrastis kentukea) as its 2015 Urban Tree of the Year.
The yearly selection must be adaptable to some harsh growing conditions and have strong ornamental traits. It is often a species or cultivar considered underutilized by urban foresters. The Tree of the Year program has been running for 19 years, and recent honorees include ‘Vanessa’ parrotia (2014), live oak (2013), Accolade elm (2012), and goldenraintree (2011).
Columbia, Missouri Natural Resources Supervisor Brett O’Brien said, “Remarkably adaptable to our state’s weather and site conditions, yellowwood is a tree which is not particularly rare, but in my opinion is certainly not planted in our area nearly enough. It could be that it is not popularized because in un-irrigated turf areas it’s apt to be a little slow; in my experience I have found that in landscape beds or irrigated areas it grows fairly quickly.”
Indeed, the consensus is that yellowwood does well in a variety of urban conditions so long as it gets adequate water. It’s best used in parks, wide tree lawns, or, with pruning, in narrow tree lawns. Yellowwood is hardy in Zones 4a to 8b and is native to eastern North America. It is a medium-maturing tree in the legume family that matures at 30 to 50 feet tall and 40 to 55 feet wide. It can handle high soil pH (up to 8.2) and is considered relatively pest free. According to Cornell’s Urban Horticulture Institute, yellowwood is easy to transplant B&B or under 2-inch caliper bare root.
This tree has elegant year-round beauty. O’Brien admires the “pendulous fragrant white flowers, reminiscent of wisteria” and “the smooth, elephant-grey to light brown bark of the tree’s trunk, as well as the lustrous reddish-brown stems.” He said that a favorite yellowwood of his is located in downtown Columbia on the west side of a red brick building, in an unforgiving site where the tree spends the early morning in deep shade and late afternoon in blazing sunlight. Nevertheless, the yellowwood has thrived.
“Yellowwood trees admittedly have a maddening branching habit, generally doing fine until the tree is about chest height, when multiple leaders and included bark become quite common,” said O’Brien. “Judicious and timely pruning can help, though at a certain point, it is probably reasonable to just accept that good branching structure is not this tree’s strong suit. Yellowwood’s other positive attributes clearly outweigh this one idiosyncrasy, and I would suggest that the value and benefit this beautiful trees provides makes consideration for planting worthwhile in many urban areas.”
A pink-flowering cultivar, ‘Perkins Pink’ is available but may be challenging to find.
The SMA recognizes the underutilized and strongly ornamental yellowwood for its service to urban forests and encourages its use when matched appropriately to site and as part of a diverse urban tree inventory.
Article provided by the Society of Municipal Arborists.
Editor’s Note: Arbor Age magazine is not affiliated with the Society of Municipal Arborists or the Urban Tree of the Year selection.
By Leonard Phillips, ASLA Emeritus
Common Name: Yellowwood
Botanical Name: Cladrastis kentukea (lutea)
Height: 30 to 50 feet
Spread: 40 to 55 feet
Form: Rounded shape, loose form, wider than tall at maturity
Bloom Period: Early summer, May-June
Flower: 1-inch long, white flowers in pendulous clusters, 8 to 14 inches long; fragrant, heavy blooms on alternate years; tree will be covered with blossoms on a good year and hardly flower on a bad year
Fruit: 2- to 4-inch, long, thin, bean-like pods which turn brown, persistent
Spring Color: Leaves open yellowish-green in spring
Summer Foliage: Mid-green in summer, dense compound leaves, 8 to 12 inches long
Autumn Foliage: Orange to yellow in autumn
Winter Color: Light gray bark is attractive in winter, excellent form is displayed in winter
Bark: Smooth, light gray, often multi-stem exfoliating bark, thin bark easily damaged
Habitat: Species native to central Southeastern United States
Culture: Needs space, rich soil, needs good drainage, tolerates high pH, as well as acid soil, sensitive to drought and compaction, full sun when young, more tolerant with age
Hardiness Zone*: 4a to 8b
Growth Rate: Fairly fast, full size in 30 years
Pest Problems: Excellent resistance, nothing serious
Storm Resistance: Generally excellent although some reports indicate weak branch crotches in major windstorms, prevented by pruning older trees
Planting: Transplant bare root or B & B from local or northern nurseries, deep roots
Pruning: Prune at planting and 3 years later to mature form; bleeds heavily if pruned in winter or spring; remove bad branches and crotch angles
Propagating: Stratified seed or cuttings in winter
Design Uses: Excellent shade tree for homes, parks and open space, equally well as specimen or in groves
Companions: Use with Galium as ground cover
Other Comments: Attractive to bees, starts to bloom when half grown, wood is yellow
Available From: Most nurseries
These are the personal observations of the author, living in New England – Zone 6. Leonard Phillips can be reached via e-mail at firstname.lastname@example.org
Note: Arbor Age magazine is not affiliated with the Society of Municipal Arborists or the Urban Tree of the Year selection. Leonard Phillips did not participate the Urban Tree of the Year selection.
Photo by Emily Hamilton