General: Kentucky coffeetree is the only member of the genus Gymnocladus native to North America. The word gymnocladus comes from the Greek for naked branch, referring to the few stout twigs, which are conspicuous year round. The word dioicus relates to dioecious, meaning there are male and female trees. The tree lies dormant for about 6 months of the year, thus the name Dead Tree or Stump Tree.
Although a member of the legume family (Fabaceae), Kentucky coffeetree is not a nitrogen “fixer”. It is a medium to large, round-barked, native deciduous tree reaching heights of 18 to 30-m with a spread of 12 to 15-m. In open areas, the tree produces an open, rounded crown, but in native woods it grows to 23-m with few branches. Large specimen trees, such as Georgia’s champion tree stands 39.6-m tall in Pickens County, are uncommon. (The National Registry of Big Trees reports a specimen Kentucky coffeetree from Lake Co., Ohio, standing at 25-m with a spread of 23.5-m and a circumference of 5.2-m at DBH). Kentucky coffeetree’s short trunk, 0.3 to 0.8-m in diameter, divides into several large branches that end in contorted, stout twigs. Its unique, thick, dark bark is gray to grayish-brown, often marked with deep, irregular furrows and plates that curl at their sides.
The alternate, bipinnately compound leaves are the largest of any native species, measuring from 0.3 to 0.9-m in length by 4.6 to 6.1-dm in width, arranged in feather-fashion in 5 to 9 pairs of pinnae, the lowest are reduced to simple leaflets. Typically the leaves consist of six to 14 entire; more or less ovate (almond shaped) leaflets, 5 to 8-cm long, acute, rounded or cuneate at the base, pubescent beneath when young, short petioled, and swollen at the base. Leaves emerge late in the spring with a striking pink-bronze color, turning to a dark bluish-green above in summer. Fall color is often a golden yellow, but the leaves drop early.
Winter buds are small, reddish, and often placed above one another in close formation (superposed). Terminal buds are absent. The buds are small, downy, almost entirely imbedded in twigs, and surrounded by a hairy ring of bark.
The stout twigs are light brown to greenish-brown with whitish patches, somewhat zigzag or wavy, large heart shaped leaf scar, with a wide salmon-pink to brown colored pith.
Flowering and Fruiting: The greenish-white dioecious or polygamo-dioecious, inconspicous flowers appear in May and June, after the leaves, and are borne in terminal racemose clusters. The fruit is a tardily dehiscent, flat, thick, woody legume that ripens in September or October and usually persists unopened on the tree until late winter or early spring. The dark brown or red brown pod is 15 to 25-cm long, 2.5 to 5-cm wide, and usually contains 4 to 8 olive-green or dark brown to almost black seed separated by a mass of brown pulp.
Wood Characteristics: The wood is of heavy density (specific gravity of 0.53 green, 0.60 dry) with a coarse, straight grain. Its sapwood is narrow and yellowish white and the heartwood is light red to red or reddish brown. It is without characteristic odor or taste. Growth rings are conspicuously ring porous, resembling ash, honeylocust (Gleditsia triacanthos L.) or sassafras [Sassafras albidum (Nutt.) Nees.]. The wood is frequently confused with that of honey locust. It must be dried carefully due to a tendency to split. It is medium strong and has good to excellent working characteristics. Occasionally, it will show considerable ring shake, but is an attractive wood for home workshops. The wood finishes to a smooth surface and “polishes superbly”. It makes beautiful paneling which weathers to a light chocolate brown. When dry, the wood is stable and machines well.
Table 1. Fuel wood facts for Kentucky coffeetree.
*140,000 BTU per gallon of fuel oil.
Table 2. Kentucky coffeetree firewood quality ratings for five factors.
Ease of Splitting
Distribution: Kentucky coffeetree is uncommon in its native habitat. It can only be found in small colonies in temperate forests. The natural range extends from New York and Pennsylvania west to Minnesota, southward to Oklahoma, and east to Kentucky and Tennessee (Schopmeyer, 1974). The species is also found in the Dakotas, Texas, Georgia, and the Carolinas (PLANTS Database); naturalized in Alabama, West Virginia, Virginia, and Delaware (Steyermark, 1975). It is believed to have been introduced into some areas by Native Americans.
For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Habitat: Kentucky coffeetree grows in moist soils in bottom-land woods or rocky open wooded hillsides with other hardwood trees. It is commonly found on limestone soils and seldom found on unglaciated sites. The tree occurs sometimes in small colonies of rather widely separated individuals resulting from root suckers. Kentucky coffeetree can be found growing in association with sweetgum, tupelo, oaks, and hickories, also black walnut, basswood, elm, and pawpaw in temperate forests.
Range and Habitat in Illinois
Regularity: Regularly occurring
Regularity: Regularly occurring
Relatively hardy in zones 3 to 8, the tree adapts well to urban conditions. It prefers full sun, humus-rich, moist soil, and tolerates drought and occasional flooding. Considering its cultural tolerances, it should be on the list of “tough” trees. Kentucky coffeetree is a fast-growing tree when young with moderate to slow growth as the tree ages attaining 3.6 to 4.3-m in 10 years.
Range and Habitat in Illinois
Seedlings may be planted in the field after one year. Transplant balled and burlapped trees into deep, rich, moist soil for best growth.
Flower-Visiting Insects and Birds of Kentucky Coffee Tree in Illinois
(Bees suck nectar or collect pollen; hummingbirds & butterflies suck nectar; observations are from Robertson)
Trochilidae: Archilochus colubris sn
Apidae (Bombini): Bombus impatiens sn cp, Bombus pensylvanica sn fq; Anthophoridae (Eucerini): Synhalonia speciosa sn
Papilionidae: Papilio troilus sn
Molecular Biology and Genetics
Barcode data: Gymnocladus dioicus
Statistics of barcoding coverage: Gymnocladus dioicus
Public Records: 5
Specimens with Barcodes: 9
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N2 - Imperiled
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Kentucky coffeetree’s numbers are declining rapidly due to over harvesting. The species is not invasive; it is only found in small clusters due to root sprouting and makes up a rare component of any woodland. In nature the seeds germinate with difficulty due to a hard outer shell. Squirrels do not cache them, so the seeds do not spread from the mother tree except along streams where the seeds may be transported by water down stream. Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
No serious insect or disease problems. Messy habit, fallen leaf stalks and pods require some clean up.
Animals should not be allowed to graze woodland areas where Kentucky coffeetree grows or where it has been cut and allowed to sprout, until spring grasses and herbage are abundant. Sprouts can be grubbed periodically as a preventative measure as only a few of these trees will be found in any woodland. Fence in large fruiting trees to prevent livestock from eating the fallen pods. This measure is desirable over removing a species that is so rare in the landscape.
Cultivars, improved and selected materials (and area of origin)
Several cultivars are available in the nursery trade including selections that are predominately male such as ‘Espresso’, ‘J.C. McDaniel’ (Prairie Titan™), and ‘Stately Manor’, that produce no fruit. Espresso exhibits an upward arching branch form resulting in an elm-like vase shape. Prairie Titan is a very symmetrical, upright spreading tree 18 to 21-m tall with blue-green summer foliage, from the University of Illinois campus near Davenport Hall. Stately Manor is a narrow, upright form 10 x 6-m wide, is possibly best for street tree use. ‘Variegata’ is a little known, slower growing cultivar with streaks of creamy white variegation and pink-purple new growth. Availability of these cultivars may be limited.
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
The seeds are oval, about 1.9-cm long with a thick, very hard, and bony coat. They have been compared to small jawbreakers only 2000 times as hard. The seeds generally remain in the pod until it falls and is broken up by decay, a process which may take 2 years or longer. The impermeable seed coat is the only hindrance to germination. A 2 to 4 hour treatment of concentrated sulfuric acid is ideal for breaking down the seed coat. Once treated the seeds imbibe water quickly and will germinate uniformly when sown. Large, bulky, purplish-brown, leather-hard pods are produced that abscise differentially from late fall into winter. The flat pods range in size from 13 to 25-cm long and 4 to 5-cm wide. Pods may be collected from the ground and run through some type of flail device to expose the seeds. The hard coated seeds will not be harmed. They can be dried and store indefinitely.
Pretreated seeds should be sown in the spring in rows spaced 46 to 76-cm apart (but no closer than 15-cm) depending upon irrigation and cultivation methods. Sow 12 to 18 seeds per 0.3 linear meter of row and cover with about 2.5-cm of firm soil. In general, about 60 to 75 percent of the seed sown will produce plantable seedlings.
Root cuttings 4-cm long and 1-cm thick may be taken in December through March. Plant the roots horizontally in pots with sand or peat. This may be the only effective way to vegetatively propagate the trees as budding is reportedly unsuccessful.
The leaves, seeds and pulp are poisonous and are toxic to livestock, humans, and pets. Sprouts eaten in the spring have produced toxicosis. Leaves, young sprouts, and seeds with gelatinous mater around them contain the toxin. Cattle have reportedly died after drinking from pools of water contaminated by fallen leaves and seeds from the tree. There is at least one anecdotal report of a human poisoning by Kentucky coffeetree.
Clinical Signs: “Clinical signs include rapid onset (within 1 hour) of intense gastrointestinal irritation, profuse diarrhea and straining, vomiting, hypertension, bradycardia, respiratory depression, muscle paralysis, and convulsions. Animals often display depression. Death usually occurs within a day after clinical signs appear.”
Fertilize with formulations that promote woody growth rather than excessive foliar growth. Prune in winter or early spring; wood may be somewhat brittle. Longer, weaker branches should be pruned when young to promote a stronger structure.
Relevance to Humans and Ecosystems
Industry: Timber, the strong, heavy wood is used in general construction, cabinet work, sills, interior finish, fine furniture, railway sleepers, bridge timbers, crossties, fence posts and rails, and fuel wood (Table 1) and (Table2). Fence posts may last for more than 50 years, although the rot resistant wood is soft and staples pull out easily. Kentucky coffeetree lumber is available but not common. The fruit is high in saponins and is used as soap. The leaves have been used as a fly poison. Due to the tree’s toxic plant parts such as the leaves and raw seeds, there is little wildlife usage as a source of food.
Ornamental: Used for ornamental purposes in large area landscape plantings and parks. In the fall, ripening pods contrast nicely with clear yellow fall foliage. Decorative clusters of the large pods rattling in the wind make for an exceptional winter ornamental. The species was introduced into cultivation before 1748. Kentucky coffeetree has been slighted in the landscape industry.
Ethnobotanic: While native to North America, Native Americans introduced the tree to some parts of the continent as they used the pulp from the wood to treat insanity. The pulp was also used in home remedies to combat fever and treat headaches. The Omahas mixed the bark of Kentucky coffeetree and gayfeather (Liatris aspera Michx.) with a pulverized portion of buffalo-gourd (Cucurbita foetidissima H. B. K.) and used it as an appetizer and tonic. A tea was also made from the leaves and pulp and used as a laxative. Certain Indian tribes reportedly roasted the beans (seeds) for food. Early settlers used the beans of the tree as a substitute for coffee. CAUTION! The seeds and pods are poisonous. They reportedly contain cytisine, a quinolizidine alkaloid and nicotinic receptor agonist, which can be dangerous. However, researchers at Indiana State University have been unable to find experimental data verifying the presence of cytisine. A single major alkaloid was found to be present in many coffeetree plant parts. The alkaloid is thought to be neutralized in the roasting process. Hydrocyanic acid has also been suggested as a possible toxin. It can be destroyed by thoroughly heating the beans for at least three hours at 150˚C. The beans contain saponins which are more toxic to fish than to other animals. Hunting tribes traditionally put large quantities of the beans in streams and lakes to stupefy or kill fish.
Pioneer settlers used the coarse-grained, light brown to reddish-brown wood in cabinetry. Children used the beans in their games.
Conservation: Kentucky coffeetree was formerly planted around farmsteads. It is tolerant to a wide range of conditions such as drought, chalk (limestone), and urban conditions. The tree has been planted on mine spoils for soil reclamation and stabilization. Due to its reasonably strong wood Kentucky coffeetree will tolerate some ice without losing branches. This pest free tree is an alternative to ash and elm where they have been ravaged by insects and disease.
The Kentucky Coffeetree, Gymnocladus dioicus, is a tree in the subfamily Caesalpinioideae of the pea family Fabaceae, native to the midwest of North America. The seed may be roasted and used as a substitute for coffee beans; however, unroasted pods and seeds are toxic. The wood from the tree is used by cabinetmakers and carpenters.
Varies from 18 to 21 meters (60–70 feet) high with a spread of 12–15 meters (40–50 feet) and a trunk up to one meter (3 feet) in diameter. A 10-year-old sapling will stand about 4 meters (13 feet) tall. It usually separates 3 to 4½ meters (10–15 feet) from the ground into three or four divisions which spread slightly and form a narrow pyramidal head; or when crowded by other trees, sending up one tall central branchless shaft to the height of 15–21 m (50–70 ft). Branches are stout, pithy, and blunt; roots are fibrous.
The Kentucky Coffeetree is a moderately fast-growing tree, and male trees are often grown in parks and along city streets for ornamental purposes. The tree is typically long-lived, healthy trees living from 100 to 150 years. The Kentucky Coffeetree sheds its leaves early during the fall and appears bare for up to 6 months. The naked appearance of the tree is reflected through the Kentucky Coffeetree's Greek genus name: γυμνοκλαδυς = "naked branch." Like the Sumac, branches are absent of fine spray; smaller branches are thick and lumpish. Because of the absence of smaller branches and its later leafing, the French in Canada named it Chicot, the dead tree. . The expanding leaves are conspicuous because of the varied colors of the leaflets; the youngest are bright pink, while those which are older vary from green to bronze.
The bark is ash-gray and scaly, flaking similarly to black cherry, but more so. The flowers are dioecious, and the fruit is a hard-shelled bean in heavy, woody, thick-walled pods filled with sweet, thick, gooey pulp. Pod length ranges from 5 to 10 inches (130 to 250 mm); unfertilized female trees may bear miniature seedless pods. The beans contain the toxin cytisine.
- Bark: Tan or dark gray, deeply fissured, surface scaly, often with prominent narrow ridges. Branchlets at first coated with short reddish down.
- Wood: Light brown; heavy, strong, coarse-grained; durable in contact with the ground, takes a fine polish. Sp. gr., 0.6934; weight of cubic foot, 43.21 lb (19.60 kg).
- Winter buds: Minute, depressed in downy cavities of the stem, two in the axil of each leaf, the smaller sterile. Bud scales two, ovate, coated with brown tomentum and growing with the shoot, become orange green, hairy and about one inch long, before they fall.
- Leaves: Alternate, bipinnately compound, ten to fourteen pinnate, lowest pinnae reduced to leaflets, the other seven to thirteen foliate. One to three feet long, eighteen to twenty-four inches broad, by the greater development of the upper pairs of pinnae. Leaf stalks and stalks of pinnae, are terete, enlarged at base, smooth when mature, pale green, often purple on the upper side. Leaflets ovate, two to two and one-half inches long, wedge-shaped or irregularly rounded at base, with wavy margin, acute apex. They come out of the bud bright pink, but soon become bronze green, smooth and shining above. When full grown are dark yellow green above, pale green beneath. In autumn turn a bright clear yellow. Stipules leaf-life, lanceolate, serrate, deciduous.
- Flowers: June. Dioecious by abortion, terminal, greenish white. Staminate flowers in a short racemen-like corymb three to four inches (75–100 mm) long, pistillate flowers in a raceme ten to twelve inches (250–300 mm) long.
- Calyx: Tubular, hairy, ten-ribbed, five-lobed; lobes valvate in bud, acute, nearly equal.
- Corolla: Petals five, oblong, hairy, spreading or reflexed, imbricate in bud.
- Stamens: Ten, five long and five short, free, included; filaments thread-like; anthers orange colored, introrse; in the pistillate flower small and sterile.
- Pistil: Ovary superior, sessile, hairy, contracted into a short style, with two stigmatic lobes; ovules in two rows.
- Fruit: Legume, six to ten inches (150–250 mm) long, one and one-half to two inches wide, somewhat curved, with thickened margins, dark reddish brown with slight glaucous bloom, crowned with remnant of the styles. Stalks and inch or two long. Seeds six to nine, surrounded by a thick layer of dark, sweet pulp.
The Kentucky Coffeetree is believed to be an example of evolutionary anachronism. The tough, leathery seed pods are too difficult for many animals to chew through (in addition to being poisonous) and they are too heavy for either wind or water dispersal. It is thus believed that the tree would have been browsed upon by now-extinct mammoths and mastodons which ate the pods and nicked the seeds with their large teeth, aiding in germination which is a behavior seen among African Elephants eating Fabaceae relatives in Africa. Because of this, its range may have been much larger than in historical times. Since it only grows well in wetlands, this is thought to be the only way the seed pods can rot away in the absence of a large herbivore to eat them.
Gymnocladus (γυμνοκλαδυς) is of Greek derivation and refers to the stout branches destitute of spray.
It is one of three species in the genus Gymnocladus, the other two being native to eastern Asia. These are Chinese Coffeetree Gymnocladus chinensis in central China, and Burmese Coffeetree Gymnocladus burmanicus in Burma.
The name is sometimes hyphenated as 'coffee-tree'; the form 'coffeetree' here is as used officially by the United States Forest Service.
The Kentucky Coffeetree is considered a rare tree species. "Rare species are those that are so uncommon that they should be monitored to determine whether their populations are becoming threatened." It is widely dispersed, but rare.
The tree's native range is limited, occurring from Southern Ontario, Canada and in the United States from Kentucky (where it was first encountered by Europeans) and western Pennsylvania in the east, to Kansas, eastern Nebraska, and southeastern South Dakota in the west, to southern Wisconsin and Michigan in the north, and to northern Louisiana in the south. It is planted as an urban shade tree across the United States and eastern Canada, including California.
This tree usually occurs as widely dispersed individuals or small colonial groups with interconnected root systems. This tree is found in floodplains and river valleys but is also sometimes seen on rocky hillsides and limestone woods. In the northeastern part of its range, seemingly natural groves of this tree are actually associated with known prehistoric village sites. In some parts of its range, this tree may be used as an indicator of the presence of limestone or of calcareous soils.
Gymnocladus dioicus is cultivated by specialty tree plant nurseries as an ornamental tree for planting in gardens and parks. The peculiarly late-emerging and early-dropping leaves, coupled with the fact that the large leaves mean few twigs in the winter profile, make it a tree that is ideal for urban shading where winter sunlight is to be maximized (such as in proximity to solar hot-air systems).
It is often planted because of its unique appearance and interesting character. There are several Kentucky Coffee trees at Mount Vernon, in the gardens along the path leading up to the house of George Washington.
Trees prefer a rich moist soil, such as bottom lands. Its growth is largely unaffected by heat, cold, drought, insects, disease, road salt, ice, and alkaline soil.
Kentucky Coffeetree is easy to grow from seed. Filing the seedcoat by hand with a small file, and then soaking the seeds in water for 24 hours will ensure rapid germination. Propagation is also easy from dormant root cuttings.
The Meskwaki also drank the roasted ground seeds in a hot beverage similar to coffee. The common name "coffeetree" derives from this latter use of the roasted seeds, which was imitated by settlers because it seemed a substitute for coffee in times of poverty. The settlers however considered it inferior to "real" coffee:
|“||When Kentucky was first settled by the adventurous pioneers from the Atlantic states who commenced their career in the primeval wilderness, almost without the necessaries of life, except as they produced them from the fertile soil, they fancied that they had discovered a substitute for coffee in the seeds of this tree; and accordingly the name of Coffee-tree was bestowed upon it. But when communication was established with the sea-ports, they gladly relinquished their Kentucky beverage for the more grateful flavor of the Indian berry; and no use is at present made of it in that manner.||”|
The plant is toxic to some animals.
In addition to use as a food, the seeds of Kentucky coffee tree were used by Native Americans for ceremonial and recreational purposes. Seeds were used as dice in games of chance that were common in eastern tribes. The seeds were also used in jewelry. Because of the importance of Kentucky coffeetree to Native Americans, they undoubtedly contributed to its dispersal.
A specimen with a height of 26 metres (85 ft) was referenced in La Turpinerie, commune of Geay, a short distance from the Charente river in south-west France, growing in a typical calcareous soil (see Minutes of Congrès international de sylviculture de Paris, June 1900). Cut during the 20th century, it had a circumference of 2.8 metres (9 ft 2 in) and was the tallest in the country at this time.
- Cirrus Digital Morton Arboretum acc. 586-81-1
- NatureServe (2009). dioicus+ "Gymnocladus dioicus". NatureServe Explorer: An online encyclopedia of life, Version 7.1. Arlington, Virginia.
- Synonyms include American coffee berry, Kentucky mahogany, nicker tree, and stump tree. Beasley, V. (9 August 1999). "Veterinary Toxicology". Ithaca, New York: International Veterinary Information Service. Archived from the original on 22 August 2006.
- "Kentucky: Adoption of the Kentucky State Tree". NETSTATE. Retrieved 2013-06-12.
- Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scribner's Sons, pp. 109–112.
- "Kentucky Trees: Gymnocladus dioicus (Kentucky Coffeetree), Pea Family (Fabaceae)". Cooperative Extension Service, College of Agriculture, University of Kentucky. Archived from the original on 24 January 2009.
- Barnes, Wagner et al. (1977). Michigan Trees
- Bronaugh, Whit (2010). "The Trees That Miss The Mammoths". American Forests 115 (Winter): 38–43.
- Moerman, Dan. "Native American Ethnobotany Database". Native American Ethnobotany Database. University of Michigan. Retrieved 9 August 2014.
- Moerman, Dan. "Native American Ethnobotany Database". Native American Ethnobotany Database. University of Michigan. Retrieved 9 August 2014.
- "Kentucky Coffeetree (Gymnocladus Dioicus)". US Dept of Agriculture. Retrieved October 2012.
- "Gymnocladus". New International Encyclopedia. 1905.
- “Clinical signs include rapid onset (within 1 hour) of intense gastrointestinal irritation, profuse diarrhea and straining, vomiting, hypertension, bradycardia, respiratory depression, muscle paralysis, and convulsions. Animals often display depression. Death usually occurs within a day after clinical signs appear.”"Kentucky Coffeetree (Gymnocladus Dioicus)". US Dept of Agriculture. Retrieved October 2012.
- Veterinary link
- VanNatta, Andrew R. (2009). "Ecological Importance of Native Americans Culture to the Kentucky Coffee Tree (Gymnocladus dioicus)". University of Wisconsin Stevens Point. Retrieved 2013-07-17.
- "London Gardens Online". London Gardens Online. 1905-08-07. Retrieved 2013-07-15.
- Sternberg, Guy, (2004) Native Trees for North American Landscapes. Timber Press, Inc.
- University of Fort Smith Tree Guide Pod dimensions.
- Personal conversation with The Morton Arboretum regarding the occasional appearance of miniature seedless pods on female Kentucky Coffeetrees.
- Hightshoe, Gary L. (1988). Native Trees, Shrubs, and Vines for Urban and Rural America: A Planting Design Manual for Envieronmental Designers. New York: Van Nostrand Reinhold. pp 216–217.
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