Kentucky Coffee Tree Growing Guide: Avoid Seeds & Pods Danger (Roasting)

Image Credit: MONGO²⁸

What Is the Kentucky Coffee Tree/American Coffee Berry? (Gymnocladus dioicus)

The Kentucky Coffee Tree, sometimes called the American Coffee Berry, is a large, native, deciduous, leguminous tree with spreading branches and striking summer foliage. Its scientific name, Gymnocladus dioicus,¹⁸ hints towards its long dormant season (Gymnocladus = “naked branch”).⁵

The Kentucky Coffee Tree is increasingly rare in the wild as the seeds require very precise conditions to germinate, requiring the tree to rely on root sprouts for reproduction.

However, this unique tree is becoming a fixture in public spaces such as parks and college campuses.¹¹

Kentucky Coffee Tree Facts

The Kentucky Coffee Tree is truly one-of-a-kind, making these Kentucky Coffee Tree facts all the more interesting.

• The Kentucky Coffee Tree is one of only six species in the Gymnocladus genus and the only species native to North America. The other five species are native to East Asia.^7,19
• In 1873, Gymnocladus dioicus became one of the first plants ever grown from seed at Harvard University’s Arnold Arboretum.¹¹
• This species was used as a non-caffeinated coffee substitute, a practice introduced by the Meskwaki Native Americans in Kentucky before coffee became more accessible.^11,19
  (Read about how to calculate your coffee carbon footprint)
• The huge, compound leaves of Gymnocladus dioicus are larger than any other native North American species!²⁰
• The wood of the Kentucky Coffee Tree is known as “Kentucky Mahogany” due to its reddish-brown tone.¹⁹
• The Kentucky Coffee Tree has a very long dormant period as it is one of the latest trees to leaf in the spring and the earliest to drop leaves in the autumn.⁸
• In prehistoric times, the seed pods were consumed by giant herbivores like the wooly mammoth, broken down by stomach acid, and excreted elsewhere to take root and grow. Without these mammals, the thick-coated seeds must lie buried and dormant until the outer layers rot away and they can germinate.⁸
• There are a few cultivars of the Kentucky Coffee Tree. Cultivars are generally male to avoid seed litter.³
• The Kentucky Coffee Tree was formerly the state tree of Kentucky, before being replaced by the Tulip Poplar in the 1990s.^9,14

How To Identify Kentucky Coffee Tree

The Kentucky Coffee Tree makes an impression in any landscape, standing as tall as 100 feet!¹⁶

Inarguably, the most distinctive feature of the Kentucky Coffee Tree is its enormous, compound leaves, but the purple brown seed pods of this species are also fairly recognizable.

In the wild, coffee trees often grow in shared areas with Hickory, Elm, and Basswood Trees. To learn more about how to identify Kentucky Coffee Trees, explore the following sections for a detailed examination of their various features.

Kentucky Coffee Tree Leaves

The deciduous Kentucky Coffee Tree leaves are truly a marvel and notable for their sheer size! Unlike the simple leaves of the Maple, Oak, Poplar and Dogwood Tree leaves, leaves of the coffee tree are compound.

The huge leaves are twice-divided or bipinnate, meaning that each leaf has many secondary veins branching from the central vein, with each secondary vein bearing many leaflets. The leaf structure is similar to that of a fern.

A single leaf can grow up to 3 feet long, and the individual leaflets may reach lengths of up to 2 inches. Each leaflet is almond-shaped with smooth (entire) margins and a slightly pointed tip.^17,20

The leaves and leaflets are arranged in an alternate fashion, and a single leaf may have more than 40 leaflets. The dark green upper side of the leaf is contrasted by a lighter green, slightly hairy underside.²³

The tree blooms late in the spring with an initial pinkish bronze tint, and the foliage turns a brilliant yellow briefly in early autumn before the leaves fall.^3,16

Kentucky Coffee Tree Seeds

The large, dark brown seeds of the female Kentucky Coffee Tree are encased in a long, leathery, purplish brown pod (up to 10 in. long and 2 in. wide). Each pod contains a few large, poisonous seeds which are woody and nut-like with a hard and thick outer coating.

The seeds are surrounded by a dark, bitter, sticky pulp. The pods often remain on the tree well into the winter season.^14,23

Kentucky Coffee Tree Flower

Kentucky Coffee Tree flowers are dioecious, meaning that individual trees bear flowers with either male or female parts, but not both.¹⁷ The greenish-white flowers are approximately 1 inch around, and they grow in panicles at the tips of branches.

The panicles of the female tree can be nearly 3 times as large as the males, growing up to 12 inches long.^14,16 The inflorescence of Gymnocladus dioicus is rather inconspicuous because the abundant foliage tends to hide the flowers.

Kentucky Coffee Tree Wood

Kentucky Coffee Tree wood has reddish-orange hues similar to mahogany, giving rise to the moniker “Kentucky Mahogany.” The twigs of this tree are very stout, and the pith is salmon colored to orange.

As it ages, the Kentucky Coffee Tree bark becomes deeply fissured or furrowed like Cottonwood Tree bark. Gymnocladus dioicus is a hardwood tree that has been used in cabinetry, wall paneling, fence posts, and rail ties.

(Want to learn more about the Janka Wood Hardness Scale?)

The wood may be confused with that of the Honey Locust (Gleditsia triacanthos). Unfortunately, over-harvesting has led to a rapid decline in native coffee tree populations and the wood cannot be easily purchased.^4,16

Planting Tips for Kentucky Coffee Tree

Kentucky Coffee Trees are extremely hardy in a wide range of environments. They grow nearly as well in urban settings as rural settings.

This section includes planting tips for Kentucky Coffee Trees, such as:

• Plant in a large, open area that receives plenty of sunlight
• Plant a male tree (seedless) or seedless cultivar
• Plant in an area away from pets and children

How Far Apart To Plant Kentucky Coffee Tree

Kentucky Coffee Trees have wide branching canopies which can spread to more than 50 feet in diameter. It is important to consider this when determining how far apart to plant Kentucky Coffee Trees, because each tree needs full sunlight.

Given its size, a single tree is likely adequate for most yards or small landscapes. Coffee trees are often found as individual organisms in the wild, and they are beautiful as stand alone landscape trees.²²

When To Plant Kentucky Coffee Tree for the Best Yield

The first step aside from knowing where to plant a coffee tree is knowing when to plant Kentucky Coffee Tree for the best yield. The Kentucky Coffee Tree acclimates best when planted during the warm seasons: spring and fall.

It should not be planted during periods of extreme heat, drought, or freeze.¹⁰

Growing Kentucky Coffee Tree From a Seed

Growing Kentucky Coffee Tree from a seed can be a challenge initially as the seed is encased in a pod and surrounded by a hard exterior coating. To get the seeds to germinate, a gardener needs to remove the outer coating.

There are a few ways to go about this, such as filing off the coating of each seed, soaking seeds in sulphuric acid, or pouring boiling water over the seeds and soaking for 24 hours.⁸

Using warm water to help the seeds scarify and germinate is probably the easiest method. Try this in the spring.

At the end of the 24 hour period check the soaking seeds for any discolor, misshapen or floating seeds and discard them. The remaining seeds can be sown immediately into pots with a 1:1 ratio of all purpose potting soil and perlite.

Water and drain the soil before making a small hole for the seed. Place pots in partial sunlight and keep the soil moist for up to 1 month, or until the seeds germinate.¹⁰

Growing a Kentucky Coffee Tree From a Seedling

Some local nurseries may sell Kentucky Coffee Tree seedlings, and there are many online nurseries which can ship seedlings at an affordable price. But for many individuals, the process will begin with them starting their own tree from seed.

Kentucky Coffee Tree seeds will usually be started indoors in small pots or trays. These can be placed outdoors in partial sunlight when the weather allows.

(Image: Eiku²⁷)

After a few months, the seedling should reach a height of 4 to 6 inches. This is usually a good time to transplant the small seedling to a significantly larger pot where it can remain for a while.

When transplanting, remember to add water and consider adding organic fertilizer as well. Some sources indicate that the young coffee tree seedling should be ready to transplant to its permanent home after its first growing season when it is about one year old.

Other sources recommend allowing the tree two to three growing seasons before transplanting it.^2,21 Be sure to choose a time for transplanting when the soil is warm, usually in the fall or spring.

A young tree with tender new growth is more vulnerable to pests. When growing a Kentucky Coffee Tree from a seedling, it is very important to protect the seedling from various insect pests such as slugs and caterpillars.

These can often be picked off by hand. Regular watering and occasional fertilization also help to increase the vigor of the young tree.

Growing a Kentucky Coffee Tree From a Cutting

While some sources suggest that it is possible to grow a Kentucky Coffee Tree from dormant root cuttings, there is little guidance available on effectively growing a Kentucky Coffee Tree from a cutting.¹²

The USDA suggests taking root cuttings during the winter that are 4 centimeters long by 1 centimeter thick.²¹

Root cuttings should only be taken from trees that are healthy and vigorous during their dormant months, and gardeners should avoid taking too many cuttings from a single organism. Young roots are preferable, and these should be cut from the main root at the crown.

After removing any lateral root shoots and small root fibers, the root cutting should be planted horizontally about 1 inch deep in a pot filled with a mixture of peat, sand, and grit. A light watering is recommended, and the pot should be placed in a weather-protected area that receives adequate sunlight.

Cuttings will usually form new growth by the following spring and be ready to transfer to a larger pot.²⁵

Best Growing Conditions for Kentucky Coffee Tree

The Kentucky Coffee Tree is a highly adaptable and tolerant tree specimen. It can thrive in a wide range of climates and soil types.

However, the best-growing conditions for Kentucky Coffee Trees are in full sun conditions with moist, rich, well-draining soils.

Kentucky Coffee Tree Growing Zone

The optimal Kentucky Coffee Tree growing zones are zones 3a through 8b, making it an ideal tree for temperate climates, essentially anywhere in the continental U.S. As this tree does not prefer climates with intense heat and excessive rain, the only places where it is unlikely to thrive are the subtropical areas along the coasts of California and the southernmost tips of Texas, Louisiana, Arizona, and Florida.

Use the USDA Plant Hardiness Zone Map to find relevant growing zones and view the growing zones for Kentucky Coffee Tree (where to grow).

Watering Needs for Kentucky Coffee Tree Plants

The watering needs for Kentucky Coffee Tree plants are very easy to meet. This hardy tree can tolerate periods of drought and rarely needs watering.

However, that doesn’t mean that the tree won’t benefit from watering. In fact, Gymnocladus dioicus can be watered as often as twice weekly in the first several weeks after planting and once weekly throughout its first growing season.

Once established, only water during periods of drought and avoid watering the leaves.¹³

How Long It Takes To Grow Kentucky Coffee Tree

Kentucky Coffee Trees start off as rapid growers, but their growth rate wanes after the first few years. Anyone wondering how long it takes to grow Kentucky Coffee Trees can expect the average tree specimen will grow about 12 or 13 feet in its first ten years.²⁰

How Much Sunlight Does Kentucky Coffee Tree Need Each Day?

Many people want to know how much sunlight does Kentucky Coffee Tree need each day. Gymnocladus dioicus requires full sun conditions year round (at least 6 hours of direct sunlight each day).

Luckily, its substantial size makes it easy for the tree to obtain adequate sunlight.

Companion Plants for Growing Kentucky Coffee Tree

Many types of plants flourish beneath the canopy of the Kentucky Coffee Tree, as its long dormant period (5 to 6 months annually) and its dappled shade create optimal conditions.

The best companion plants for growing Kentucky Coffee Trees are native flowering shrubs and herbaceous plants which thrive in partial sun and shade.

(Image: NasserHalaweh³⁰)

Lawn turf grows very well around this tree where it receives adequate sun.³

How To Stop Kentucky Coffee Tree Disease

Most likely, gardeners will never need to know how to stop Kentucky Coffee Tree disease because Kentucky Coffee Tree disease prevention occurs naturally. Since the coffee tree is poisonous to animals, animals usually steer clear of these trees and subsequently, they can’t transfer diseases from other trees.

In the rare case where a coffee tree does become diseased, prune and remove diseased twigs and branches to prevent spreading.¹

Common Pests of the Kentucky Coffee Tree

Remarkably, the Kentucky Coffee Tree really has no major pest problems. A couple of common pests of the Kentucky Coffee Tree include leafrollers, spider mites, and scales but these typically cause little damage and don’t require either chemical or natural pest control for Kentucky Coffee Tree.¹⁵

Kentucky Coffee Tree Pros and Cons

The Kentucky Coffee Tree is a great tree for many reasons, but it also has a few drawbacks. View the table below for a summary of Kentucky Coffee Tree pros and cons.

Toxic Kentucky Coffee Tree Seeds and Pods

Anyone growing a Gymnocladus dioicus tree specimen must be cautious of the toxic Kentucky Coffee Tree seeds and pods, particularly if animals or children use the area. The seeds and pods of this tree contain the toxic alkaloid cytisine.

This toxin is supposedly neutralized when the seeds are roasted, and roasted beans can be used to make a coffee substitute, for seasoning, and other culinary purposes.⁸

Individuals who aren’t interested in using the seeds may elect to plant a male Kentucky Coffee Tree which will not produce the dangerous and messy pods.

(Image: MONGO²⁹)

A very unique tree in the North American landscape, the Kentucky Coffee Tree has served many purposes and filled many roles over time. Present day, foraging of the coffee tree ‘beans’ has become a hobby for some people who use the roasted seeds for culinary flavoring.

With native populations dwindling, this popular, low-maintenance tree is now cultivated as a landscape plant on golf courses, campuses, parks, and gardens! Use the growing and tree care guide in this article to learn a trick for how to grow the Kentucky Coffee Tree from seed today!

Frequently Asked Questions About Kentucky Coffee Trees