By John Olive, Retired Director, AU Ornamental Horticultural Research Center, www.mobilecountymastergardeners.org
As the days grow shorter and the temperatures slowly begin to drop, a gardener’s fancy often turns to putting the garden to bed for the winter. Here on the Gulf Coast, veteran gardeners know that fall and winter is a good time to garden. With a few exceptions, it is also the best time to plant trees.
The traditional fall (September and October) can be very hot and dry along the Gulf Coast. For the purposes of this article, consider fall on the Gulf Coast as late October through mid-December. These dates are not carved in stone but are a block of time that is consistently after the dry fall and before the extreme cold that occurs some years in late December.
Along the Gulf Coast, it is best to wait until the typical dry fall period ends, and rains become more likely. Of course, every year is different, but this window is safe most years. Planting in the fall allows more time for trees to establish good root systems. A strong root system is a big plus when the summer heat and dry weather arrive, and helps the tree survive extreme late winter hard freezes.
Planting at the optimal time will not guarantee success, but it is a good start. To improve success in planting a new tree, it is good to review some general planting tips. Bigger is not always better. Often choosing a smaller tree over a larger tree is best. The larger tree may look good in the pot, but larger potted trees may be root-bound and have a relatively small root system, unable to support a large top. Not always, but often, a tree purchased while small will catch up and surpass the larger tree, once settled into the landscape.
Dormant, deciduous trees with no leaves require less water and focus their energy on root growth. Though the tops are dormant, the roots continue to grow throughout the winter. This winter growth gives the tree a head start before bud break in the spring. Even evergreen trees slow down in winter, use less water, and concentrate more energy toward root growth.
Dig a wide hole but not a deep hole. The hole should not be much deeper than the pot you are planting. Most horticulturists suggest not adding soil amendments to the planting hole. Fill the hole with the same dirt that came out of it. Adding peat, potting soil, or organic matter often creates a nice but confined environment, like the original pot, that the roots will not want to leave. They often won’t venture out into the surrounding soil because it is so nice right there in the original hole. A little additional organic matter is okay, but don’t overdo it. You want the roots to grow out from the original root ball.
One final tip to remember is to remove the sod from around the trunk and do not allow grass to grow right up to the trunk. Grass roots are very aggressive, will use a lot of water, and will take water from the planted tree. If grass is allowed to grow right up to the trunk, the tree may be damaged by weed trimmers and mowers. To avoid this, apply a thick organic mulch around the base of the tree but not so much as to create a ‘mulch volcano’ as described by Alice Marty in a recent Lagniappe article (09/06/2023).
There are a few exceptions to the fall planting rule.
Citrus and hardy tropicals are better planted in the spring. Then these cold susceptible trees have all summer to develop a good root system and therefore are better prepared to survive cold weather. If planted in the fall, the roots do not have time to get established, making the tree vulnerable to severe weather.
Trees from pots can be planted year-round but planting in fall greatly increases the chances for a healthy and long-lived tree. Just in time for fall planting, Mobile Botanical Gardens will have a selection of native and non-native trees at the Fall Plant Sale October 26, 27, and 28.