Black walnut (Juglans nigra) and hickory (Carya) trees are both common sights in forests and woodlands across much of eastern North America.
They are large deciduous trees that produce edible nuts and valuable timber.
While they share some similar characteristics, there are also important differences between these two types of nut-producing trees.
- Black walnut trees grow taller (up to 100 ft) while hickories are shorter (60-80 ft) at maturity.
- The leaves of black walnut have 15-23 leaflets; hickory leaves have 7-9 larger leaflets.
- Black walnuts produce round "cannonball" shaped nuts; hickory nuts are oblong with a thin husk.
- Black walnut wood is heavier and harder; hickory wood is elastic and shock-resistant.
- Black walnut trees have allelopathic juglone that inhibits other plants; hickories do not.
- Both trees provide edible nuts for wildlife and humans, valuable timber, and ornamental interest.
- Black walnuts thrive in deep fertile soil and are native to northeastern North America.
- Hickories grow across a wider range including south-central states and have shaggy, ridged bark.
Appearance and Growth Habit
Black walnut trees typically reach mature heights of 100 feet or more. They have an open, spreading canopy and straight trunks that can be over 3 feet in diameter.
The bark is dark and deeply furrowed.
Hickory trees are smaller, usually reaching about 60-80 feet at maturity. They have an irregular, oval-shaped canopy and shaggy gray bark with long ridges.
The leaves of both trees are pinnately compound, meaning they have multiple leaflets arranged along a central rachis or stem.
Walnut leaves normally have between 15-23 leaflets, each 2-3 inches long.
Hickory leaves are larger overall, with 7-9 leaflets that may reach 6 inches long.
Black walnuts grow relatively fast when young, but their growth rate slows with age. Hickories grow moderately fast throughout their life span.
Both trees are fairly long-lived, typically over 100 years.
Flowers and Fruits
Black walnuts produce separate male and female flowers in the spring.
The male flowers are yellow-green catkins that dangle from the branches.
Female flowers are tiny, spherical and green. After pollination, the female flowers develop into round green fruits 2-3 inches across.
These mature in the fall into the familiar brown "cannonball" shaped walnuts.
Hickory flowers are also catkins, but they emerge from the branch tips. The male catkins are slender, yellow and up to 6 inches long.
Female flowers occur in spikes of 2-5, and develop into somewhat pear-shaped or oblong fruits.
Hickory nuts have a thin outer husk that splits open at maturity in the fall.
The hard, wrinkled shells of both black walnut and hickory nuts encase sweet, oily kernels. These nuts are prized by both wildlife and humans.
Bark and Wood
Mature black walnut trees have very dark, heavily ridged bark with deep furrows running vertically along the trunk.
Hickory bark is tighter and lighter gray in color, with interlacing narrow ridges that give it a shaggy appearance.
The hard wood of both trees is known for its strength, hardness and shock resistance.
However, black walnut wood tends to be heavier, harder and more weather resistant than hickory.
The rich, brown heartwood of walnut trees is particularly valued in furniture making and other applications.
Hickory wood is commonly used for tools, baseball bats, bows and other products requiring elasticity and stiffness.
Habitat and Range
Black walnut and hickory species share similar habitat preferences and overlapping native ranges.
They both occur naturally in moist forests and bottomlands throughout the central and eastern United States.
Their ideal growing conditions include deep, fertile soil and abundant sunlight.
Black walnut has a more northerly distribution, extending into Canada and the upper Midwest.
The hickories' range extends farther west and south into Texas and Mexico.
Both trees are also widely planted well outside their native ranges.
These large nut trees have important ecological benefits.
Their nuts are a valuable autumn food source for wildlife including squirrels, deer, bears, foxes and birds.
Flowering catkins also provide pollen or nectar to insects and other pollinators. The trees' deep root systems help prevent erosion on slopes and riverbanks.
Black walnut trees produce natural chemicals called juglone that suppress the growth of many other plant species under or near them.
This gives mature walnuts a more open understory. Hickories do not have this allelopathic effect on nearby vegetation.
Both types of trees provide shade, nesting sites, cover and perching spots for birds and other wildlife.
After dying and decaying, the rot-resistant wood of fallen walnut and hickory trunks provides habitat for cavity nesters, reptiles and amphibians.
Uses for Humans
Beyond their edible nuts, black walnut and hickory trees have many uses for humans.
Their hard, strong wood is made into furniture, flooring, veneers, lumber and wood products. High-quality walnut timber is especially prized for its rich color and luster.
Hickory wood is used for tools, sporting goods, fuel and smoking wood for meat.
These trees are also grown ornamentally in parks, yards, golf courses and other landscaping.
Their flowers, leaves, bark and form provide visual interest and shade. Specifically, black walnuts are popular specimens prized for their massive size and spreading canopy.
Hickories are valued for their shapely, more compact form and attractive bark.
Black walnut and hickory trees are American classics, providing beauty, shade, wildlife food and habitat along with high-quality wood.
While similar in many ways, walnuts reach a larger size while hickories have distinctive shaggy bark and large, fragrant leaves.
Both continue to fill important roles in both forests and human spaces.