- Kentucky Coffeetree
- Gymnocladus dioicus: Kentucky Coffeetree1
- General Information
- Use and Management
- Kentucky coffeetree
- Tree & Plant Care
- Disease, pests, and problems
- Disease, pest, and problem resistance
- Native geographic location and habitat
- Bark color and texture
- Leaf or needle arrangement, size, shape, texture, and color
- Flower arrangement, shape, and size
- Fruit, cone, nut, and seed descriptions
- Cultivars and their differences
- Related posts:
Additional information: The Kentucky coffeetree belongs to the pea or legume family. Although many members of the legume family have an association with a bacterium that converts gaseous nitrogen into a usable form, the Kentucky coffeetree cannot “fix” nitrogen.
Although widely distributed, this tree is a rare forest tree and occurs in scattered populations. The national champion Kentucky coffeetree, 97 feet tall, is in Maryland.
The fruit of Kentucky coffeetree is a typical legume pod,but the flowers are not the typical pea-like form most people associate with legumes. There is some evidence to indicate that the Kentucky coffeetree was introduced into Kentucky by Native Americans, who used pulp from its wood to treat insanity. A tea made from leaves and pulp was used as a laxative. The seeds of Kentucky coffeetree were used by early settlers as a substitute for coffee. However, caution must be taken because the seeds and pods are poisonous. They contain the alkaloid cystisine that can be dangerous. Cystisine is thought to be neutralized in the roasting process. Cattle have died after drinking from pools of water containing fallen seeds and leaves from Kentucky coffeetree.
Gymnocladus dioicus is the botanical name for the Kentucky coffeetree. Gymnos is the Greek word for “naked” and klados is Greek for “branch.” This name refers to the large, coarse branches (without smaller twigs) that remain after the rachis and petiole of the bipinnately compound leaves fall. The species name, dioicus, refers to the tree’s dioecious nature.
Because leaves of this tree are late to emerge and early to fall, the Kentucky coffeetree is without leaves, or naked, much of the year. Kentucky coffeetree has the largest leaves of our woodland trees. The bark is rough and furrowed and the older branches terminate in a flower cluster, forcing new branches to form in a “zig-zag” pattern. Kentucky coffeetree has reasonably strong wood and will tolerate some ice without losing branches.
To see a Kentucky coffee tree (Gymnocladus dioicus) in the wild is a rare event. Each year your chances of doing so are diminishing. This interesting and beautiful legume is quite rare, growing in small scattered populations throughout eastern and Midwestern North America. Presettlement records hint that its rarity in nature is not necessarily a recent phenomenon either. It seems that, at least since humans have been paying attention, this tree has always been scarce.
Despite its rarity in the wild, the Kentucky coffee tree has gained a lot of popularity as a landscape tree. It is an attractive species with contorted branching and large, airy leaves. It’s about this time of year when folks start wondering if they have killed the new tree they planted last fall. I often hear complaints from folks new to this species that their trees must have lost their buds over the winter. The reason for this lies in its generic name. “Gymnocladus” is Greek for “naked branch.” The leaf buds are not exposed like they are in other tree species. Instead, they are imbedded within the twigs, hidden under a hairy ring of bark. Kentucky coffee tree does not leaf out until late spring, well after most other trees have broken dormancy.
In the wild, Kentucky coffee tree can be found growing on floodplains and, very occasionally, scattered through upland habitats. As such, water has been invoked as the only known dispersal agent. This is a strange mechanism to call on as nothing about this tree (other than its current habitat) suggests adaptations for water dispersal. Its seed pods are quite heavy, chock full sweet pulp, and don’t float very well. What’s more, the pods often remain on the tree all winter and the large seeds within require ample scarification before they will germinate. They are toxic to boot.
Even more perplexing is just how well this species does when planted outside of floodplains. It seems equally at home growing in a yard or along the sidewalk as it does on a floodplain. Taken together, all of these clues seem to suggest that the Kentucky coffee tree is missing something. Perhaps it is missing a preferred seed disperser?
The megafaunal dispersal syndrome has become a sexy topic in ecology. Essentially it posits that North America was once home to a bewildering array of large mammals that flourished leading up to the end of the Pleistocene. With that many large animals haunting this once wild continent, many have suggested that North American vegetation evolved to cope with and even exploit their presence. Certainly we see this happen on a smaller scale with things like birds and small mammals. We see it on a much larger scale with animals like elephants and rhinos in Africa and Asia. Could it be that when the Pleistocene megafuna went extinct in North America, the plant species they dispersed suffered a huge ecological blow?
The limited range of species like the Kentucky coffee tree would certainly seem to suggest so. Though it is a hard theory to test, the fruits of this tree seem adapted to something much more specific than running water. The large pod, the sweet pulp, and the hard seeds would suggest that the Kentucky coffee tree requires a larger mammalian herbivore to eat, scarify, and pass its seeds. No animal native to this continent today does the trick effectively. Most animals avoid the seeds entirely, which is likely due to their toxicity. Sure, the occasional seed germinates successfully, however, based on its limited natural range, the fecundity of the Kentucky coffee tree has been diminished.
Photo Credit: Roger Latourwww.floraurbana.blogspot.ca
Gymnocladus dioicus: Kentucky Coffeetree1
Edward F. Gilman and Dennis G. Watson2
This is a medium-growing tree that will reach a height of about 70 feet while spreading 45 to 60 feet. The state tree of Kentucky should be used more often because it is adaptable to many soils, including alkaline, has interesting bark and grows with an open canopy allowing light to penetrate to the ground for adequate turf growth beneath the canopy. The coarse branch texture in the winter is also quite unique, forming an interesting silhouette of only several large branches. Large seed pods hang on the tree in the winter but can be a litter problem when they fall in the spring. They are very hard and can be `shot’ from a lawnmower running over the fruit. Male trees are sometimes available and they do not set fruit, but this is often unreliable. The seeds (in a 5 to 10-inch-long pod) and leaves may be poisonous to humans. The pod contains seeds which used to be roasted as a coffee substitute. The leaves are bipinnately compound and can be up to 18 inches long, resembling walnut.
Middle-aged Gymnocladus dioicus: Kentucky Coffeetree
Scientific name: Gymnocladus dioicus Pronunciation: jim-NOCK-luh-dus dye-oh-EE-kuss Common name(s): Kentucky Coffeetree Family: Leguminosae USDA hardiness zones: 3B through 8B (Fig. 2) Origin: native to North America Invasive potential: little invasive potential Uses: street without sidewalk; reclamation; shade; specimen; highway median Availability: somewhat available, may have to go out of the region to find the tree Figure 2.
Height: 65 to 70 feet Spread: 45 to 60 feet Crown uniformity: irregular Crown shape: oval Crown density: open Growth rate: moderate Texture: medium
Leaf arrangement: alternate (Fig. 3) Leaf type: bipinnately compound, odd-pinnately compound Leaf margin: entire Leaf shape: elliptic (oval), ovate Leaf venation: pinnate Leaf type and persistence: deciduous Leaf blade length: less than 2 inches Leaf color: green Fall color: yellow Fall characteristic: showy Figure 3.
Flower color: white/cream/gray Flower characteristics: not showy
Fruit shape: pod or pod-like, elongated Fruit length: 6 to 12 inches, 3 to 6 inches Fruit covering: dry or hard Fruit color: green, brown Fruit characteristics: does not attract wildlife; showy; fruit/leaves a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; showy; typically one trunk; thorns Pruning requirement: little required Breakage: resistant Current year twig color: brown, green Current year twig thickness: very thick Wood specific gravity: unknown
Light requirement: full sun Soil tolerances: clay; sand; loam; alkaline; acidic; well-drained Drought tolerance: high Aerosol salt tolerance: moderate
Roots: not a problem Winter interest: yes Outstanding tree: yes Ozone sensitivity: sensitive Verticillium wilt susceptibility: unknown Pest resistance: free of serious pests and diseases
Use and Management
The trunk normally grows straight up through the crown and is very strong. Branches grow at wide angles to the trunk and are usually well-spaced along the trunk. This configuration adds to the durability of the tree. Be sure that major limbs are kept at less than about half the diameter of the trunk to ensure that they remain well-attached to the tree. The crown is round or oval in youth, becoming more upright and oval with age.
Some people object to the sparse branching when this tree is young, but some pruning to create more branches can help. Any shortcomings of the tree are made up by the almost total lack of insect or disease problems. Lawns grow well beneath the tree due to the light shade cast by the thin, open canopy.
Kentucky Coffeetree is well-adapted to urban soil and could be used more often and, like most trees, does best when provided with irrigation until well-established. Amazingly tolerant of drought and poor soil once established although it is native to rich bottomland soil. Used as a street tree in some communities. Be careful using the tree in a lawn since the pods could become projectiles from mowing equipment.
Male cultivars without fruit should be available soon. These will be well-suited for planting along streets.
Propagation is by seed, or grafting male plants.
Pests and Diseases
No pests or diseases of major concern.
This document is ENH446, one of a series of the Environmental Horticulture, UF/IFAS Extension. Original publication date November 1993. Revised December 2006. Reviewed February 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.
Edward F. Gilman, professor, Environmental Horticulture Department; Dennis G. Watson, former associate professor, Agricultural Engineering Department, UF/IFAS Extension, Gainesville, FL 32611.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.
U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
Kentucky Coffeetree in Spring with bare branches except for the prior years seedpods still attached to branch tips.
Eloise Butler wrote in 1914 “In winter, a more intimate acquaintance can be made with deciduous trees. For it is only after the leaves have fallen that the architecture of trees can be clearly discerned. Every species has a different form. No individual, ever is exactly like another.” (1)
So, what is that dead tree over there? Rough bark, stubby sparse branches, bare twigs – it appears deceased except for those funny pouches on the end of some branches. You are looking at a Kentucky Coffeetree in the winter. Those ‘pouches’ are the past season’s seedpods, the branches are stubby and sparse by design as they have to support the largest leaves of any native North American deciduous tree. Bare twigs – the tree hides its buds until just before the leaves pop out. It’s scientific name is Gymnocladus dioicus. The first part is from two Greek words meaning ‘naked’ and ‘branch’ – the appearance when not in leaf. The second word, dioicus, meaning ‘separate houses’ is used when the flowers of the tree are of one sex only and trees of the male sex must be close by for the female flowers to be pollinated and produce the seed pods.
Kentucky Coffeetree in late Spring fully leafed-out.
Kentucky Coffeetree grows up to 80 feet in height with a rounded to open crown depending of how much space it has. As trees go, this one has attractive, quite striking, flowers with a purple calyx, whitish petals, yellows on the reproductive parts – its in the Pea Family (Fabaceae) where you usually find colorful attractive flowers.
Eloise Butler liked it but it was not found in her Garden as it is native to the counties south of the metro area, so she obtained some selections from the Park Board nursery, which at the time, was located in Glenwood Park, of which her Garden was a corner of. . Eloise’s successor, Martha Crone, really liked the tree; she planted 36 of them in 1934 and more in 1949. It is without doubt that those large ones on Geranium Path and Violet Way in the Garden are those early trees.
Today, the Coffeetree is so rare in the wild that it is listed on the Minnesota DNR’s ‘Special Concern’ List. It is also becoming rare in other parts of North America. Fortunately, it is planted in many public spaces. I see it frequently in a number of public parks and the Minnesota Landscape Arboretum has a number of them gracing the hillside of the new sculpture garden – but none so large as those in the Garden.
The female flowers of the Kentucky Coffeetree
A Park Board official wrote in 1975 “Over the last century the Park Board has planted a number of these interesting trees throughout the city. Most parks have at least one of them. The largest of these are two Kentucky Coffeetrees growing on either side of Minnehaha Creek just upstream from the point where Lake Nokomis flows into the creek.” (2)
Now to the matter of that name – Coffeetree. It was not a good tasting beverage. Francois Michaux said it best: “The name of Coffee Tree was given to this vegetable by the early emigrants to Kentucky and Tennessee, who hoped to find in its seeds a substitute for coffee; but the small number of persons who made the experiment abandoned it, as soon as it became easy to obtain from the seaports the coffee of the West Indies.” (3) Michaux also noted that those early emigrants sent the tree to France in late 1700’s where it thrived in and around Paris. Maybe their descendants are still there.
Below: The leaves are bi-pinnately compound, the largest leaves of any North American native species.
My Kentucky Coffeetree
All that is required to grow the tree is a seed, space and patience – especially the latter. Wait till Spring and find one of the seed pods that has overwintered on the tree or on the ground below the tree. The seeds will be ready to germinate. There are usually 4 to 6 seeds per pod embedded in a sticky pulp. Most critters avoid eating the seed as they contain a toxic alkaloid called cystisine, so its not hard to find pods. Find an open space where the tree has room to grow. The 3/4 inch seed, should be scarified and just-covered with soil, watered and put a little fence around it. I started mine in a small pot, which requires planting in the ground by Autumn or the root development will be hindered.
The dark seeds of Kentucky Coffeetree just beginning to sprout.
Now comes the patience part. Some say the tree is fast growing at first then it slows down; commentary perhaps from someone who never grew one. My tree has been in the ground six years now and it is six feet high. It looked nice when it had those large compound Summer leaves but after leaf-fall it was just a stick, that is, until year six when I saw near the top of the stick a short stub. Finally a branch! Yes, in year six several leaves developed on the stub and now it will begin to look like a real tree – sometime – as after leaf-fall I still have a stick, but with a stub near the top. I wonder what sex it is – will it be female and have fragrant flowers and maybe get pollinated from some male in a near-by park and make seeds? or will it be male and just have flowers? I will never know. Most deciduous trees require decades before flowering and bearing fruit. Maybe the next steward of my plot of land will find out – or the person after that – but hopefully the tree will survive and add another touch of interest to the landscape.
(1) Annals of the Wildlife Reserve, 1914, unpublished.
(2) Mr. Gordon Morrison, Coordinator of Environment Education for the Minneapolis Park Board, The Fringed Gentian™, 1975
(3) Francois Michaux, The North American Sylva or A Description of the Forest Trees of the United States, Canada and Nova Scotia, Vol. 1, 1819.
Kentucky Coffee Tree (Gymnocladus dioicus)
In 1967, several specimens of Kentucky Coffee Tree were planted near the Arboretum Shop area. Over time, the original trees died and were removed, but numerous root sprouts have survived forming two small groves around the stumps. Kentucky Coffee Tree is found throughout Tennessee and ranges from southern Ontario to northern Louisiana and Georgia and west to Oklahoma, Kansas, eastern Nebraska, and southeastern South Dakota. Kentucky Coffee Tree was designated the State Tree for Kentucky in 1976, but legislation was enacted in 1994 to replace it with Tulip Poplar.
Kentucky Coffee Tree belongs to the Pea family (Fabaceae). It grows to heights of 60 to 70 ft and has very large compound leaves (1 to 3 ft long by 1.5 to 2 ft. wide). These alternate, compound leaves are bipinnate (i.e., twice compound) with a central rachis having pinna bearing 6-14 leaflets, 1-2 in. long. The genus name Gymnocladus, from the Greek meaning “naked branches,” refers to the coarse branches without twigs that are evident in the spring and winter when the large leaves are absent. The dark grayish brown bark has deep fissures with scaly ridges. The reddish brown wood – referred to as “Kentucky Mahogany” – has been used by woodworkers and cabinet makers, and is prized for interior millwork, bridge timbers, and railroad ties. It also is often used as a street tree. Kentucky Coffee Tree is dioecious, having male and female flowers on different trees. The large black to brown seed pods (3-8 in. long) contain seeds with very hard coats that were roasted by early American settlers as a coffee substitute – the basis for the common name “Coffee Tree.” The leaves and uncooked seeds are potentially toxic.
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Tree & Plant Care
Transplant in sites with deep, rich, moist soil.
Consider male cultivars to avoid messy fruit.
Disease, pests, and problems
No serious pests.
The tree’s leaves and seeds are poisonous.
Disease, pest, and problem resistance
Tolerant of high pH, drought, and pollution.
Native geographic location and habitat
Native to the Midwest. Often found along streams and in flood plains.
Bark color and texture
Bark is dark brown; rough, becoming scaly with curved edges.
Leaf or needle arrangement, size, shape, texture, and color
Alternate, bipinnately compound leaves; with numerous leaflets; lowest set of leaflets simple.
Leaflets, oval with entire margins and blue green color; mild yellow fall color.
The whole leaf is 36 inches long and 24 inches wide.
Flower arrangement, shape, and size
Long (8 to 10 inch) spike-like clusters of greenish white flowers; male and female flowers on separate trees.
Fruit, cone, nut, and seed descriptions
5 to 10 inch long, red-brown, leathery pods containing a few large rounded seeds on female trees.
Male trees are seedless.
Cultivars and their differences
“These plants are cultivars of a species that is native to the Chicago Region according to Swink and Wilhelm’s Plants of the Chicago Region, with updates made according to current research. Cultivars are plants produced in cultivation by selective breeding or via vegetative propagation from wild plants identified to have desirable traits.”
Espresso (Gymnocladus dioicus ‘Espresso’): Arching branches provide a vase-shape; male cultivar.
Prairie Titan™ (Gymnocladus dioicus ‘J.C McDaniel’): An upright, spreading male selection.
Stately Manor (Gymnocladus dioicus ‘Stately Manor’): Male cultivar with a more narrow, upright form.