Yellowwood

Basic Information
Tree ID: 
163
Family: 
Fabiceae
Genus and species: 
Cladrastis kentukea
Description: 
The Kentucky Yellowwood (also known as American Yellowwood or simply the “Yellowwood”) as its name suggests, is found throughout the South-Eastern United States, primarily Kentucky, Tennessee, and Arkansas although it is rare in the range. It is typically small to medium sized, although it can grow to be 30-feet high with a canopy area of 40-55 feet. It is a dicot and deciduous, meaning it loses its leaves in the winter. “Yellowwood” is a reference to the yellow color of its wood when it's been freshly cut, and its leaves change to a bright yellow during the fall. It’s a slightly late bloomer, flowering in late spring like in early June.
Surveyors: 
Ingrid Moore, Ashley Sottosanti, Karinne Tennenbaum
Location
Area: 
Marsh and Farnam Gardens
Collected Data
Tree shape: 
Round
Date of tree entry: 
02/08/2024
Height: 
9.20 m
Diameter at breast height: 
9.88 m

Bark
The bark of the Kentucky Yellowwood is very smooth and a light brown or gray with gray and white patches. The bark of a sapling is yellowish green and develops into a reddish brown as it ages. It develops texture or an elephant-skin appearance as the tree ages.
Twigs & branches
The Kentucky Yellowwood has smooth, shiny, reddish-brown branches. The genus name Cladrastis has Greek origins as the combination of klados (meaning “branch”) and thraustos (meaning “fragile”). Thus, together they mean “brittle branch” that refers to the fragility of the twigs. These branches are fragile and vulnerable to harsh weather conditions, including high winds and blizzards. The name “yellowwood” comes from the fact that this tree’s wood contains a yellow dye that allows for a unique wood color. The stems have light-colored pores that allow for gas exchange.
Foilage
Leaves are pinnately compound (arranged along a middle vein) and vary between 8-12 inches long. They alternate branching and have 7-11 leaflets that are each about 2-4 inches long. Buds start appearing in early-to-mid-March and leaves grow around late-April - this is quite a bit later in New Haven. Leaves are pale green when they come out in the spring and turn to a dark green over the summer. In the fall, they are a beautiful bright yellow before dropping for the winter. The leaves lack hair.
Reproductive Structures
Kentucky Yellowwoods are slow-growing in their early years, are hermaphroditic, and have perfect flowers, meaning they have both male and female parts. They are most commonly pollinated by bees and butterflies. The flowers are small and white with yellow middles, and grow in a hanging fashion. The number of flowers on each tree is quite variable, and every 2-3 years these trees flower quite heavily. These flowers are then replaced with the pod-like fruits.
Fruit
The Kentucky Yellowwood is classified as a legume and typically develops hanging yellow-brown or yellow-green fruits in late August. The pods each contain 2-6 seeds, and become ripe in the fall.
Seasons
  • Winter
  • Spring
  • Summer
  • Fall
Research
Natural range of distribution: 
Habitat: 
The Kentucky Yellowwood is found across the southeastern United States east from North Carolina and west to Oklahoma. It can be found scattered in southern Indiana through to Alabama. It is most commonly found in the Bluegrass region of Kentucky along the Kentucky River. It is best suited for USDA Zone 4. Its range is very fragmented though which makes it one of the rarest trees found in the eastern United States. It thrives best in well-drained soil and full sun.
Origin, history, and uses: 

The Kentucky Yellowwood was found by botanist Andre Michaux in 1796. The Kentucky Yellowwood is the only one found in the US but there are other Yellowwoods found across Asia. In 1994 it won the Pennsylvania Horticultural Society Gold Award and selected as the Urban Tree of the Year in 2015 by The Society of Municpal Arborists.

Believe it or not, the Kentucky Yellowwood gets half its name from the distinct yellow color of its heart wood when recently cut. This was used as a dye by early Appalachain settlers. The wood was then used to make gunstocks, furnitire, and for decorative wood pieces. While out of fashion now for furniture use, the Yellowwood is often planted as an ornamental tree.

It has a wide canopy area perfect for shade and beautiful, fragrant flowers. These trees are drought and pest resisitant. This makes them excellent for garden planting, but they are susceptible to damage and require lots of pruning which makes them poor urban street trees. This provides excellent habitat for nesting songbirds and high-quaility nectar. It is fairly cold tolerant and resistant to most pests and diseases, making it an excellent garden plant. Although, due to its deep roots, this tree is very difficult to tranpsplant.

Phenology: 
In the southern end of its range, the Kentucky Yellowwood blooms around mid-May. The tree first flowers when it reaches between 12 to 18 feet. It has a slow growth rate ad continues until it's 30 to 50 feet tall. The flowering season is very variable and it won't flower every year. About every second year, the Kentucky Yellowwood experiences a very heavy flowering season. The tree has incredible, yellow fall foliage. It is deciduous so drops its leaves in the winter. This particular tree in New Haven will most likely begin to flower in late June as this is very northern for its range.
References: 
  1. https://www.uky.edu/hort/Yellowwood
  2. https://greatplainsnursery.com/product/american-yellowwood-2/
  3. https://mortonarb.org/plant-and-protect/trees-and-plants/yellowwood/
  4. https://plants.ces.ncsu.edu/plants/cladrastis-kentukea/
  5. https://www.wildflower.org/plants/result.php?id_plant=CLKE
More
Other information of interest: 

The largest documented Kentucky Yellowwood is found in Spring Grove Cemetery in Cincinnati, Ohio. It is 22 meters tall with a 2.2 meter trunk diamter.

Media and Arts
“The Road Not Taken”
Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;
 
Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,
 
And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.
 
I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I—
I took the one less traveled by,
And that has made all the difference.
 
-Robert Frost (1915)

To the tune of “Frere Jacques” 

  • “Yellow woo-oood, yellow woo-oood”

  • “How you’ve grown, how you’ve grown”

  • “Cladrastis kentukea, cladrastis kentukea” (pronounced “cla-drastis kentucky-a)

  • “We’re proud of you, so proud of you”

-Karinne Tennenbaum

Comments

Ingrid Moore on April 25, 2024: