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SMA 2015 Urban Tree of the Year: Yellowwood

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)

Parentage: Native

Family: Fabaceae

Introduction: 1812

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 lenphillips@on-line-seminars.com


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

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