Part 3 of 3:
The ABCs of successful tree planting:
Follow-up care fore new plantings

By Jack Radecki

Once planted, hopefully the right tree in the right place as described in parts I and II of this article(1), trees are all too often left to fend for themselves. This is especially true for contracted work.

     As was mentioned in previous articles, it was proven that up to 95 per cent of the tree's root system is removed at time of harvest, particularly when the tree is machine dug into a wire basket. In most cases, newly planted trees cannot reestablish their root systems without the appropriate after care. I recommend to all my students, and especially landscape contractors, that they encourage their clients to buy into a follow-up care program. This not only provides more work for the industry, it is vital for tree survival. As a rule of thumb, there should be a year's worth of intensive after care for every inch of caliper of the transplanted tree, with the primary focus being on an appropriate watering program.

Water stress is the most severe problem facing newly planted trees. With a diminished root system, the newly planted tree cannot absorb enough water to counteract the transpiration of moisture through the leaves, especially on sunny days. During periods of drought, caliper trees should receive at least 10 gallons of water twice per week. The use of either a root feeder or a saucer area helps to prevent run off.

     Mechanical devices such as tensiometers or issometers measure the amount of moisture in the soil, but it is difficult to overwater any tree planted in a properly drained site. Caution needs to be exercised, however, if trees are planted in low, wet or poorly drained sites.

     Scientific research data is now available to support the use of drip irrigation systems. According to Dr. Roger Funk of the Davey Tree Co. (Ohio), drip irrigation produces large mats of fibrous tree roots. Rain jet or oscillating systems, on the other hand, are less effective, being susceptible to evaporation, run-off and uptake by turf. Moisture left on foliage overnight by overhead systems also promotes the development of fungal diseases.

Mulching provides a tree with a number of benefits, as it:
  • retains soil moisture;
  • stabilizes soil temperature;
  • provides a barrier zone for two of any tree's worst enemies, namely the weed eater and the lawn mower;
  • wood mulch decomposes and releases nutrients into the soil in the form of organic matters, which also helps to condition the soil. If we are worried that it takes large amounts of nitrogen to break down wood chips, we must also remember that the nitrogen is again released into the root zone after decomposition;
  • controls the growth of weeds and turf; and
  • mulch provides an aesthetic quality to the landscape.

     Woodchip, generally obtained from tree care operations, is the most commonly used type of mulch. Other forms include bark chips, broken clay tile, gravel and geotextiles. Ground asphalt, obtained from road resurfacing applications, can also be used as mulch, and even paving can be used as mulch for a newly planted tree.

     A maximum depth of two inches is recommended. Too much mulch can cause girdling, as tree roots will rise to the surface with more air, rather than growing out into the soil. Excessive use of mulch can also provide a home for rodents. At the base of the stem, keep the mulch depth to one inch, as excess moisture can be a breeding ground for phytophthora fungus (basal stem root rot).

Do not fertilize at planting time, especially in the spring, as fertilizers can cause a tree to use its carbohydrate reserves, resulting in the growth of long, succulent shoots which do not harden off properly. This also promotes a greater root-shoot imbalance. The best time to fertilize is in the fall, after the shoots have hardened off and after at least one full growing season. Dr. Funk has proven that the nutrients provided by fertilizers are used strictly by the root system after the top of the tree has stopped growing.

     While it is commonly believed that phosphorous is the main ingredient required for healthy root growth, we, in fact, need to be more concerned about the presence of an adequate supply of nitrogen. Most of our soils contain an abundance of phosphorous, while nitrogen, which is required in large quantities, readily leaches away from the soil. In the maintenance of large, weak trees, a fall fertilizer using 30-10-7 blue nitroform powder with a hydraulic liquid injection system can produce some very dramatic results.

     For smaller trees planted for at least one full year, a 10-6-4 fertilizer can be applied at the rate of one or two pounds per caliper inch of tree. The fertilizer can be broadcast over the rooting area or, for larger trees, two-inch holes can be drilled to a depth of 12 inches at 12- to 24-inch intervals. About one-half cup or four ounces of fertilizer should be placed in each hole to achieve the recommended rate of application.

To develop an ideal branching structure, a young tree should be pruned four to five times within the first 10 years, depending on the variety. Corrective pruning at time of planting was covered in a previous article(1). Subsequently, trees should be inspected every two to three years for interfering, horizontal and double leader branches. Depending on the species, we usually try to develop a scaffold systems of branches equally spaced (i.e. eight to 12 inches apart) with one true leader.

     Depending on the species and location of the tree, we should also remove one or two temporary branches from the bottom of the crown to provide for an appropriate stem height. There are exceptions, of course, as we would never want to raise the stem height of a copper beech, for example. Except in rare circumstances, conifers do not need to be pruned at all. As they mature, it may be desirable to remove some of the lower dead growth.

Soil conditions and turf
Although we provide as large a soil volume as possible, tree roots will still grow to the outer edges of the planting pit. Aeration and the addition of organic matter to the peripheral root zone are required for trees as they mature. Fertilization alone is not enough. There are several technologies available to help alleviate soil compaction, including a new air-spade technique that blows compressed air into the soil.

     All too often on urban sites, tree roots are cramped into the top six inches of soil, which is designated for turfgrasses. Turfgass is a tree's most serious competitor for nutrients, and wherever possible, we should consider the California model, which utilizes ground covers, shrubs and mulches, together with trees in landscaped frontages.

     Tree planting is an investment in any urban landscape situation, and deserves to be treated as such with an adequate after care program. Only in this way can we ensure our investments will increase in value and provide us with the many shade, cooling, air cleaning and aesthetic benefits we have come to expect of trees, our "guardians of the earth."

Jack Radecki is the Supervisor of Arboriculture Services for The Mount Pleasant Group, where he has been employed for the past 22 years. Experienced in all maintenance aspects of trees and with extensive knowledge of nurseries, landscape design and planting, Mr. Radecki is an expert in tree identification and selection. He shares his knowledge with the trade and public through seminars, continuing education courses at community colleges and tree study tours, as well as on a consulting basis in landscape appraisals, hazard tree evaluation, diagnostics and species/site matchings. A Graduate Forester from the University of Toronto (B.S.C.F.), Mr. Radecki is registered Arboricultural Consultant with the American Society of Consulting Arborists, director and past president of the Ontario Shade Tree Council, and member of the International Society of Arbiculture, the Seneca College Advisory Committee Environmental Landscape Management and the Sir Sandford Fleming College Advisory Committee, Urban Tree Maintenance Program.

(1) See also, Part I, "Know your trees and their growth requirements," May 2000, and Part II, "Prepare the site before planting," June 2000.