Planting the Trees is part three of four in the Street Trees: Site Selection, Planting, and Maintenance in the Urban Landscape series.
After the tree species and size have been selected, the site properly prepared, and the planting hole dug, you are ready to plant the tree. All plants brought to the site should be stored in a shady area, watered daily, and protected from drying winds and temperature extremes. Fine root hairs are very sensitive to physical and environmental damage. Damage to the roots cannot be seen immediately but will show up later in reduced growth and disease and insect problems.
B&B, as well as containergrown trees, should be carried by the root ball. Carrying trees by the trunk or rough handling of the root ball can damage the roots. Containers and synthetic burlap and all ties or tags should be removed or dropped into the bottom of the hole. Regular, untreated burlap (treated burlap is green) may be left on the root ball if none shows above the soil line. Burlap above the soil line will have a “wick effect,” drying the root ball.
Be sure that the tree is straight in the planting hole and the top of the root ball is even with or slightly above ground level. For bare root plants, spread roots out evenly in the hole. Do not wad or jam roots into the hole! Begin backfilling up to two-thirds the height of the root ball using the same soil that came out of the hole. Fill the remainder of the hole with water and allow the tree to settle. Add the rest of the soil. If you are planting in sandy soils or on slopes where infiltration is a problem, use remaining soil to make a 3- to 4-inch berm or raised area surrounding the root ball. Be sure the berm is well beyond the edge of the root ball so water will be directed to the right place. Do not pile soil around the base of the tree. If drainage is poor, a berm is not recommended as you would not want to direct any additional water to the hole.
Mulching is essential to Mulching is essential to the successful growth of young trees. Mulch helps conserve and extend available water to the tree, reduces competition by suppressing weeds, moderates temperature extremes, and acts as a barrier or visible marker for damaging landscape maintenance equipment. Organic mulches support microbial activity important for tree establishment and growth.
Too much mulch can be harmful. Only 2 to 3 inches of pine straw or bark will be sufficient to provide weed control and moisture retention for the tree. Coarser mulches such as pine bark nuggets and pine straw do not support the growth of weeds as much as the finer compost materials. Herbicides can be used for additional weed control. Advances have been made in this area and products are available that are safe for the plants and are non-toxic to our environment. Contact your county Extension agent for help in selecting the right herbicide for your planting needs.
A commonly used mulch is black plastic. Black plastic suppresses weeds, but it also limits water infiltration and gas exchange. Roots under this material are usually concentrated at the surface where oxygen is available. Additional mulch is required for aesthetics. This mulch is usually washed away or decays to expose ugly, weathered black plastic. Black plastic is not a good choice for mulch.
Fabric mulches are more effective than black plastic, but additional organic mulch is still required for aesthetics. This material can also be exposed and become an eyesore. Another drawback is that weed seeds can blow into the mulch, germinate, and grow through the fabric. Despite its limitations, fabric mulches are alternatives and provide initially better weed control than organic mulches by themselves. Each situation will need to be evaluated on the basis of economics and available labor. Extend the mulched area 2 to 3 times the diameter of the planting hole to encourage root growth into the surrounding soils.
Staking and Guying
Staking and guying of trees is only necessary in windy locations, in areas of heavy traffic, or in situations where the tree will not stand up by itself (this should not happen if proper tree selection is made). Be sure to use a nonabrasive material such as flexible hose or nylon stockings to prevent rubbing and girdling of the tree. Never use wire even if protective foam or other guards are used. Staking is designed to prevent the tree from blowing over in high winds—not to restrict movement of the trunk. Any staking should allow flexing of the trunk. This flexing contributes proper taper development and strength of the trunk. Any stakes that are close to the root ball area should be driven through the root ball and into the native soil for good support. One or two growing seasons should be sufficient for getting the tree established so that the ties can be removed with the possible exception of extremely large trees (greater than 8-inch diameter). Be sure that these ties are removed!
Tree wraps, used for protection against sun scald on thin-barked trees, are rarely needed in Alabama. Wraps are sometimes used on fruit trees or pecan trees but rarely on ornamental shade trees. Some of the materials can cause more damage than help. Moisture accumulates behind the wraps and often creates optimum conditions for insects and diseases. New products are becoming available that are treated with pesticides to prevent this problem should wraps ever be required.
If possible, develop a 6-foot diameter sod-free buffer zone around the tree to protect the tree’s root zone from foot traffic and competition and to protect the tree’s trunk from injury. Use open paving stones instead of solid concrete or asphalt to allow water penetration and gas exchange. If traffic and compaction are going to be a problem, divert traffic through the use of landscape plantings or barriers, or use raised planters or elevated grating to protect the root zone.
Once the tree is planted, a maintenance program should be implemented to monitor water, insects, and disease. Water is crucial during the first and second growing seasons. Irrigation should be part of the initial planning. Drip irrigation is the preferred system. Neither water trucks nor dragging hoses provide the regular watering that trees require. The expense is partially offset with reduced labor, increased survival, growth, and establishment.
Fertilizer is not required for the first year if the soil has been properly prepared and fertilized as indicated by the soil test. Normal recommendations for fertilizing shade trees for maximum growth in an unrestricted area is 2 to 4 pounds of nitrogen per 1,000 square feet. This is usually applied in a split application in January and again in mid- to late June. However, in a street-tree environment, with a tree under stress and with a limited exposed root zone, dumping this amount of nitrogen in a 4- x 4-foot area could be disastrous. Fertilizer rates must be reduced to fit the size of the exposed area. Make more frequent applications or use slow-release fertilizers. This is also true for sandy soils where nitrogen leaches readily from the soil.
A method that is not recommended here is to apply ¼ to ½ pound of nitrogen per inch diameter at breast height. This method is rarely applicable for the urban setting with restricted, exposed root zone areas. Do not use this method for fertilization. If slow-release forms of nitrogen are used, up to 6 pounds of nitrogen could be applied per 1,000 square feet. To prevent damage to turf areas, never apply more than 3 pounds of actual soluble nitrogen per 1,000 square feet.
Street Trees: Site Selection, Planting, and Maintenance in the Urban Landscape series