Carya illinoensis pecan variety Candy. (Photo by Tom Pope)

For Release On Or After 12/20/13

November through February is the best time to plant pecan trees. But before you decide to add a pecan tree to your landscape, there are some things to consider.

Pecan trees grow to be quite large – 60 feet tall with a spread of 40 feet – so make sure your site is large enough. In addition, the wood of pecan trees is somewhat brittle. You should not plant a pecan in a location where branches might fall on your house or other structures. Pecan trees should be planted at least 20 feet (preferably more) away from homes, garages, patios, etc.

Recommended varieties for Louisiana include Elliot, Candy, Sumner, Houma, Caddo, Oconee and Melrose. They are more resistant to diseases and are better suited for home landscapes. Pecans must be cross pollinated to produce well. Generally, most areas have enough pecan trees for this to happen if you plant only one tree.

Pecans are wind-pollinated, and the pollen can travel a significant distance. However, if your area has no pecan trees, you should plant two different types – an Elliot, Candy, Sumner or Melrose with a Houma, Caddo or Oconee.

Planting pecan trees

Survival is usually better when you plant smaller-sized 4- to 5-foot trees grown in containers. Never allow the roots of the trees to dry out prior to planting. Dig large holes for planting – two to three times the diameter of the root ball and the same depth.

Prune badly damaged and dead roots from the trees before planting. Place the root ball of the tree in the hole and fill back in around it with the soil you dug out.

It will be important to water young trees during periods of dry weather, especially during summer the first and even second years after planting. Mulches should be used around newly planted trees to conserve moisture and prevent weeds.

Why pecan trees fail to bear

Home gardeners are sometimes perplexed to discover that their pecan trees have failed to produce well. First, you must consider the length of time since planting. Pecan trees generally take 6 to 10 years after planting before they begin to produce good crops of nuts. Only time and patience can correct this issue.

In some cases, the trees that once produced abundant nuts now, years later, produce few if any pecans. Trees may also produce nice crops of nuts, but the quality leaves a lot to be desired with nuts that are poorly filled or contain no meat at all. What has gone wrong? Is there any way pecan trees can be brought back into production and maintained?

Healthy leaves are essential

Think of a pecan tree as a very complex factory where leaves are responsible for producing the food that is ultimately used to produce nuts. It takes about 40 pecan leaflets to set and fill out a single pecan nut.

During the growing season, foliage manufactures food, which is translocated and stored in the root system to produce nuts the following spring. Early leaf loss can result limited or reduced nut production the following year. Foliage damage during the growing season also can reduce the current year’s crop.

Early leaf loss can be the result of a combination of problems, especially a disease called scab. Scab is a fungal disease that appears early on the leaves and nuts as small black lesions, which later enlarge and completely blacken the leaves, eventually killing them and causing defoliation.

Scab also will attack and damage the shuck or outer covering of the pecan and result in a poorly filled or hollow nut. If you see numerous black spots, streaks or areas on the shuck of the pecan and the nuts are poorly filled, pecan scab is the problem.

In addition, various leaf-feeding insects can compound problems. Insects such as aphids, mites and fall webworms attack pecan leaves, contributing to early defoliation.

The pecan variety dictates the severity of the pecan scab problem. Many older varieties, such as Stuart, Success, Mahan and Desirable, are very susceptible to scab disease. On the other hand, varieties listed at the beginning of the column are moderately to very resistant to the scab organism.

Pecan varieties not considered scab resistant can only be kept in production by applying fungicides throughout the growing season. Pecan trees are too large to be sprayed with conventional garden equipment, and most gardeners do not have spray equipment that will reach the top of a 30-foot tree.

Another factor helpful in maintaining productive pecan trees is an annual application of fertilizer. Pecan trees should be fertilized in February with about one pound of general-purpose fertilizer per inch diameter of the trunk measured 3 feet from the ground. Do not fertilize young trees the first year they are in the ground.

Pecans are an important part of our culture and cuisine, and it’s nice to have plenty of them to use and share from your own tree. Just remember that sufficient room, proper variety selection and good care are important to success.

Rick Bogren