Benjamin K. Cooper, Undergraduate Research Assistant *
Gary R. Johnson, Associate Professor, Urban and Community Forestry *
Tree stem protection, commonly referred to as tree wraps, can serve two basic functions:
- stem protection from physical (mechanical) damage and
- modify the stem’s ambient environment. Physical or mechanical protection may protect the stem from equipment, animal, vandalism and herbicide damage. The stem-ambient conditions that potentially may be modified by protection materials are air temperature and humidity.
Facts And Myths: What Information Is Research-Based?
Secured incorrectly, any tree wrap can be a detriment. Most problems occur due to three common situations:
- the wrap is applied too tightly to the stem, allowing no airspace between the material and the stem,
- the material is left on too long, and
- the material is attached to the stem with another material that does not decompose soon enough to avoid stem girdling (constriction) [Fig.1].
Any material that is applied directly to stem tissues may trap moisture, which may lead to more cases of stem diseases, decay, and infestations of certain insects that can damage stem tissues [Fig. 2]. Most commonly, the insects that prefer tightly wrapped stem conditions are woodborers and wasps with wood-boring larvae. It has also been observed that tightly wrapped stems have larger lenticels, which may or may not be a health issue. Leaving a tightly attached, synthetic or rot-proof wrap on the stem for too long, or using synthetic materials to attach the wrap to the stem may girdle the stem [Fig. 3].
As the stem expands during growing season – even the first growing season – the rigid materials may compress (girdle) the stem tissues. This compression may restrict water, nutrients and/or photosynthates from normal movement within the stem, or weaken the stem physically. Other protectants such as paint and slaked lime may chemically damage the stem tissues.
A wrap that minimizes temperature changes within the stem environment should be the most helpful in preventing sunscald or frost cankers [Fig. 4a-c]. Studies have been conducted that indicated that wrapping tree stems with paper wraps provided no more benefit than leaving the stems bare. Research has also shown that wraps with reflective material on the outside and insulation on the inside considerably moderated temperature fluctuations in the air surrounding the stem as well as the stem tissues.
Wraps should not be left on tree stems for more than one year. Never attach wraps to stems with materials (synthetic twine, plastic, wires) that will not decompose within a year.
Numerous materials have been used to protect tree stems. The most commonly used materials include:
- paper wrap (kraft paper)
- latex paint
- commercial plastic guards
- homemade guards
Guards and wrapping materials may be purchased at lawn and garden centers. For larger orders, contact Ben Meadows Company (1-800-241-6401) or Forestry Suppliers (601-354-3565).
Plastic guards can be used to prevent physical damage to trees [Fig. 5]. They can prevent the bark from animal, lawnmower and string trimmer damage [Fig. 6, 7]. Seemingly small mechanical injuries can eventually be the demise of the tree when decay fungi or disease pathogens enter through the wounds. A simple alternative to guards is the installation of a mulch ring around the base of the tree [Fig. 8]. Mulch has other benefits, too, but does eliminate the need to mow or trim around the base of the tree.
Wraps. Stems should be wrapped from the bottom (near soil line) to the top (first set of branches) to keep water from seeping in between the wrap and stem. The top should be attached with a stretchable material, such as masking tape or light twine, that will decompose naturally within a year [Fig. 9a & b]. Never use fiber-reinforce tape, nylon cord or wires to attach the wrap to the stem. They could girdle the stem. Wraps may be installed any time but they must be removed within a year.
Guards should be loose enough to allow air to flow through the space between the stem and the guard [Fig. 10]. This will allow the guard to better moderate the ambient stem conditions, especially temperature and humidity. Many guards have holes in them to aid in this process. Like wraps, guards may be installed any time, but may cause girdling and excess stem moisture conditions if left on for too long. Guards, like wrapping materials, should be removed within a year or at least before the stem out-grows the guard diameter [Fig.11-13].
Any use of guards or other stem protection materials can best be summed up by a statement made by Bonnie Appleton, who has researched and authored several articles on stem protection: “Regardless of the reason for using a trunk protective material, there is no point in providing protection at planting if the material used may eventually damage the tree because of improper material selection, or nonremoval. Timely readjustment or removal is mandatory, for both tree growth and aesthetic reasons.” [Fig. 14-15]
Appleton, B.L. 1995. Use and misuse of tree trunk protective wraps, paints and guards. Florida Urban and Community Forestry Newsletter 1995(Spr): 2.
Appleton, B.L. and S. French. 1992. Current attitudes toward and uses of tree trunk protective wraps, paints and devices. Journal of Arboriculture 18(1): 15-20.
Harris, R.W. 1999. Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines. Prentice Hall, Englewood Cliffs, NJ 687 pgs.
Hart, J.H. and G.K. Dennis. 1978. Effect of tree wrap on the incidence of frost crack in Norway maple. Journal of Arboriculture 4:226-227.
Litzow, M. and H. Pellett. 1983. Materials for potential use in sunscald prevention. Journal of Arboriculture 9(2): 35-38.
Owen, N.P., C.S. Sadof and M. Raupp. 1991. The effect of plastic tree wrap on borer incidence in dogwood. Journal of Arboriculture 17(2): 29-31.
Watson, G.W. and E.B. Himelick. 1997. Principles and Practice of Planting Trees and Shrubs. Savoy, IL: International Society of Arboriculture. 199 pgs.