Selecting, Planting, and Pruning Trees
By Matt Grubisich, Regional Urban Forester, Texas A&M Forest Service
Trees do wonderful things.
They shade your home or business, cutting your summer cooling bill and raising your property value. Trees and shrubs provide food and cover for songbirds and other wild creatures. Cool, green foliage creates a peaceful setting where you can deal with the stresses of daily life. Around your community, trees cleanse and cool the air, buffer wind and noise, protect water quality, prevent soil erosion, screen unsightly areas, and provide a setting for outdoor recreation.
For all the benefits trees provide, it’s worth spending a little time getting them off to a good start.
Generally, late fall through early spring is the best time to plant a new tree. Most shade and ornamental trees sold in the nursery trade are either balled-and-burlaped (B&B) or container grown. B&B trees should be planted as early as possible, preferably before bud break. Container-grown trees can be planted later in the season because there is less disturbance of the plant’s root system.
Selecting a Tree
Select a tree that is suited for your site. Native tree species are usually a good choice because they are adapted to local soil and rainfall conditions. Be careful! Just because a tree is native to Texas does not mean it will work in your yard. If you need advice, check with the county extension office, your city parks department, the Texas Forest Service, or a nursery professional.
Select a tree with a straight, dominant trunk and well-spaced lateral branches. Avoid “bargain” trees with a small root ball or deformed branch structure. Trees with low, slingshot crotches may require substantial pruning in order to develop a healthy crown. The root ball should be firm and moist, and the trunk and branches should be free of damage.
Planting The Tree
Loosen the soil in your planting site to a depth of 12 inches using a shovel, or tiger. Work an area 2 to 5 times the diameter of the root ball. This will provide hospitable conditions for the tree to send out roots. Do not add organic matter (compost or peat) to the loosened soil.
In the center of the planting site, dig a hole to the depth of the root ball. Set the tree in the hole so that the top of the root ball is level with the surrounding soil. When removing a tree from its container, take care to avoid breaking the root ball. Position the tree and backfill with a little soil to hold it in place. Twine, wire, and burlap should be cut and pulled down off the root ball of B&B trees.
Backfill with soil removed from the hole. Do not add organic matter to the backfill. As you fill the hole, use water to settle air pockets. Tamp the soil lightly, but do not compact the soil around the root ball.
Build a small dam around the base of the tree with soil from the hole. This will help hold water while it percolates into the soil. Spread 3 or 4 inches of mulch (compost, wood chips, etc.) over the entire planting site. Avoid piling mulch directly against the base of the tree.
If your tree seems to need additional support, use two or three 6-foot stakes pounded into the ground outside the root ball. Attach the tree to the stakes with wide nylon webbing. The traditional method of using rope or wire cushioned with a piece of garden hose may be effective, but it can cause damage to the tree. Whatever the method of attachment, the tree should have enough freedom to sway in the wind so it can develop strength. The stakes should be removed after the first growing season.
Fertilizer probably is not needed. If you want to fertilize, use a slow-release fertilizer that is high in nitrogen. Some nurseries carry packets of slow-release fertilizer for trees that can be tossed into the hole along with the backfill.
Pruning Young Shade Trees for Strength and Form
A new tree in your landscape holds the promise of great things to come: cool shade on a hot afternoon, branches for children (and adults) to climb, rustling leaves, and maybe a splash of color in the fall. Like any youngster, your tree will need some discipline in order to live a long, productive life. You can think of careful pruning as a way of training your young tree to grow strong and healthy.
Recently Planted Trees
A good branch structure actually starts in the nursery. When you select your tree, try to find one with a strong, dominant trunk and evenly spaced branches. Double leaders and low, “slingshot” crotches can create problems down the road.
When you plant a new tree, you shouldn’t have to do any corrective pruning the first year. Plan to start your pruning regimen before the second growing season. Give your tree a little pruning help every year during the first five or six years after it has been planted. Then it will be well on its way to having a strong branch structure, and you can walk away from it for another five or ten years.
What To Prune
- Double Leaders: Try to maintain a dominant trunk for at least six to eight feet without a major fork. If the trunk divides into two or more relatively equal stems, favor one strong stem and remove the others. In some cases, you may need to do this gradually over several years. Cut one stem back to a lateral branch and let the other fill-out and become dominant. After a year or two, remove the less-dominant stem altogether. The rule of thumb is to prune-out no more than one-third of the crown in a year, but on young trees, you may be able to push the limit a little higher to remove a double leader.
- Rubbing Branches: Eliminate branches that arc rubbing or will soon rub against another branch. Frequently, one branch will grow back toward the interior of the crown and cross several other branches. Removing this one branch may solve several problems.
- Crowding: Give each branch room to grow with minimal competition for sunlight. Your goal is to have major lateral branches evenly spaced eight to ten inches apart along the trunk.
- Narrow Branch Angles: Sometimes two branches will form a narrow, v-shaped crotch. As the two stems grow thicker each year, bark may be trapped between the two stems, preventing them from forming a strong union. This is called “included bark.” Branches with included bark at the point of attachment are more susceptible to failure under load from wind or ice. Occasionally, otherwise healthy limbs on mature shade trees will fail on a clear calm day – with potentially tragic results – because of included bark. If you see bark becoming pinched between a branch and the trunk, remove the branch before it grows large enough to become a hazard.
- Sprouts and Suckers: Fast-growing sprouts that shoot out of the trunk or main limbs have a weak point of attachment. If they are allowed to reach a large size, they may break during a storm and cause serious damage to the tree.
- Temporary branches: While the tree is young, it may have small lateral branches along the main trunk. You can leave them on the tree for the first few years because they will help it develop a thicker trunk. Starting at the bottom, remove one or two of them each year until you reach the height you want the first permanent limb.
The Proper Pruning Cut
At the base of each branch, you will see a slight swelling where it joins the trunk or main limb; this is called the branch collar (see graphic, below). The ideal pruning cut angles away from the main stem just beyond the branch collar. The finished cut will leave a little bump on the main stem, but not a pronounced stub.
When cutting a large branch with a saw, the weight of the branch may cause it to sag and peel bark down the side of the tree before the cut can be finished. Use the three-step method when removing a large limb. Make a cut on the bottom side of the branch, about one-third of the way through (1). Make a second cut on the top of the branch an inch or so beyond the undercut (2). This will remove most of the weight of the limb without peeling bark. Finish the cut by removing the stub that is left (3).
Image via Texas A&M Forest Service