Cooler weather, especially winter, is perfect for planting trees and shrubs in south Louisiana.

Planting in winter gives the trees several months to establish roots before they begin active above-ground growth. And establishing those roots is fundamental to growing healthy trees.

Also, trees planted in winter require less water because of lower temperatures and slower growth.

Much like people, many plants slow down during cold winter months. Roots largely responsible for moving water, nutrients and gases through the plant, however, will continue those activities.

So now is the time to plant that pecan tree you've been wanting. But keep this in mind: Pecan trees grow to be very large — up to 60 feet tall and 40 feet wide.

At a minimum, pecan trees should be planted 20 feet away from any buildings or structures — farther is better.

Pecan wood is relatively soft and brittle, so you're going to have lots of branches falling out of your tree.

Pecans are wind-pollinated. The pollen travels pretty far, so if a nearby neighbor has trees, great. If not, you need to plant at least two trees to get pecan trees to make nuts.

A number of recommended pecan varieties for growing here are Elliot, Candy, Sumner, Houma, Caddo, Oconee and Melrose, which are more resistant to diseases and are better suited for home landscapes. It's recommended that you plant two different types. Good combinations are Elliot, Candy, Sumner or Melrose with Houma, Caddo or Oconee.

Plant a container-grown tree that's 4 to 5 feet tall. Never allow the roots of the trees to dry out prior to planting.

Dig a hole two to three times the diameter of the root ball and the same depth as the container. Loosen the root ball when planting, and be sure to remove dead roots or prune them if they have become potbound. Place the root ball of the tree in the hole and fill around it with the soil you removed from the hole.

As with all trees, it is essential to water heavily at the time of planting and for the next two weeks to get good root growth. Water young trees during extended drought periods, especially during the first and even second summers after planting.

Mulch around newly planted trees to help conserve moisture and prevent weeds. Do not fertilize your trees the first year after they have been planted. Beginning year two, trees should be fertilized annually in February. Apply 1 pound of general purpose fertilizer per inch diameter of the trunk measured 3 feet from the ground.

Once a tree is growing, it may not make nuts for six to 10 years because it puts all of its initial energy into establishing roots.

Healthy leaves are essential for nut production. It takes about 40 pecan leaflets to set and fill out a single pecan nut. During the growing season, foliage manufactures food that is used and stored in the root system for nut production the next spring. Early leaf loss can limit or reduce nut production the next year. Foliage damage during the growing season can also reduce that year’s crop.

Early leaf loss can result from a combination of problems, especially scab, a fungal disease that appears early on the leaves and nuts as small black lesions that later enlarge and completely blacken the leaves, eventually killing them and causing defoliation. Scab can attack and damage the shuck or outer covering of the nut and cause a poorly filled or hollow pecan.

Leaf-feeding insects can worsen the problems. Insects such as aphids, mites and fall webworms attack pecan leaves, contributing to early defoliation.

The pecan variety dictates the severity of the scab problem. Many of the older varieties — Stuart, Success, Mahan and Desirable — are very susceptible to scab disease. Pecan varieties not considered scab-resistant can be kept in production only through the application of fungicides throughout the growing season. Large pecan trees can be difficult to spray with typical garden equipment available to consumers. Planting disease-resistant trees is your best defense.

Email questions to gardennews@agcenter.lsu.edu.