It may seem like a silly question, but it definitely has merit! We do not see walnut trees in our area all too often. When I do, it is typically a black walnut (Juglans nigra). They tend to not be as hardy here on the coast as they are in more northern areas, although they can be grown in USDA hardiness zones 4 through 9. On the other hand, pecans (Carya illinoinensis) dot roadsides and old homeplaces across the coastal plains. There are remnants of orchards in every county I serve.

Walnuts and pecans both belong to the same family, Juglandaceae or the Walnut Family. So, how do we tell the difference between the two? Of course, the easiest way to tell the difference is the nut. Walnuts are round and resemble a green ball about the size of a baseball with a solid hull over the nut. The hull of the walnut takes a decent amount of work to separate.

Pecans are elliptical in shape and have a shuck that remains green until it splits, revealing the nut beneath. Tree structure is similar, although pecan trees will grow much larger in our area than black walnuts. Bark texture and bark color are very similar between the two trees but walnuts tend to have a somewhat rougher texture.

Both trees have pinnately compound leaves. This means that instead of single leaves on a petiole, they have multiple leaves on a petiole called leaflets. Herein lies one of the differences between the trees. Pecans have between 11 and 17 leaflets and walnuts have between 15 and 23 leaflets. A petiole is the stem-like appendage that supports the leaf away from the main stem. These trees both produce catkins and as such are wind-pollinated.

There is a difference in the size of the leaves. Pecan leaves tend to be a little smaller, measuring 12 to 20 inches in length. The color of the leaves tends to be a darker green on the upper side and a pale green on the underside. The shape of the leaflets tends to be long (2.5–7 inches) and lance-shaped, with tips that curve like the shape of a sickle. Walnut leaves measure 12 to 24 inches with individual leaflets ranging from 2.5 to 5 inches long. Although both leaves are lance-shaped, walnut leaflets tend to have longer points and are more symmetrical. Walnut leaflets will be covered in tiny hairs on the underside. Walnut leaves tend to be a much darker green than pecans.

Black walnuts were often planted around old homesites as well. The nuts were an acquired taste, often used in cooking. Black walnut trees are allelopathic. This means they release a toxin into the soil that makes growing many other plants nearby almost impossible. I have received multiple calls from gardeners whose vegetables aren’t growing only to find they have a walnut tree in proximity to their garden.

One of the best things you can ever do for your trees is to make certain they are properly planted. This is a process that begins with selection of good tree stock from the nursery. Next, dig a hole that is two to three times the size and depth of the root ball. If the tree was grown in a container, care must be taken to prune out any circling roots. This is one of the biggest issues I find on trees! These circling roots will continue to circle until they eventually cut other existing roots and/or girdle the tree. The result is a slow death of the tree. Plant your tree so that the first root is no more than 1 inch below the soil surface. This can be somewhat difficult to judge, I like to use a 2×4 piece of lumber laid flat across the planting hole to judge the soil surface. It is okay for the roots to be a little high because they will settle in with the first few rains. However, what you do not want to do is elevate the roots and mound the soil up high on the trunk. This practice stresses the tree and leaves it susceptible to all sorts of damage to the trunk. The same can be said for planting too deep, this will spell certain death for a tree. Gently compact soil around the roots as you fill the planting hole and then water your new tree in well.

If you are planting a tree this time of year, make sure to give it plenty of water. Although a containerized tree can be planted anytime of the year, the best time to plant a tree is in the late fall or early winter. Anytime a plant is disturbed or transplanted, the feeder roots need to be regrown. Planting during the dormant season allows these roots to have time to establish before they have to go to work in the spring of the year.

If you are in the market for a walnut or pecan tree, stop by your local extension center to learn all of the nutty facts surrounding these and other trees!

If you have a horticulture question, call the Extension Master Gardener volunteers in Beaufort County or Gene Fox at 252-946-0111. Email Gene at gene_fox@ncsu.edu. Your question might just make the paper!

Gene Fox is the area consumer horticulture agent with N.C. State Cooperative Extension.