Forest Service 

Northeastern Forest 

Experiment Station 

Effects of Herbicide Release 

on the Growth of 8- to 

12-Year-Old Hardwood 

Crop Trees 

G. W. Wendel 

Neil I. Lamson 
Abstract 

In 8- to 12-year-old Appalachian hardwood stands, crop trees were released by 

stem injecting competing trees with a 20 percent aqueous solution of glyphosate. 

Species released were black cherry, red oak, and sugar maple. Release treatments were (a). injection of all trees within a 5-foot radius of the crop tree bole 

and (b) injection of all trees whose crown touched the crop tree. Five-year diameter growth of all species was significantly increased by both release treatments, 

but height growth was not affected by either treatment. Survival of released crop 

trees was higher and crown-class retrogression of released trees was less than 

unreleased trees. Glyphosate was effective in controlling most hardwood species 

during the 5 years of observation 

The Author 

G. W. WENDEL, research forester, received a B.S. degree in forestry from Iowa 

State University in 1951, and an M.F. degree from Yale University in 1957. He 

joined the Northeastern Forest Experiment Station's Timber and Watershed 

Laboratory at Parsons, West Virginia, in 1962. 

NEIL I. LAMSON received his B.S. and MS. in silviculture and forest soils from 

the State University of New York College of Environmental Science and Forestry. 

He joined the USDA Forest Service, State and Private Forestry, in 1972. Currently he is a research forester in timber management at the Timber and Watershed Laboratory in Parsons, West Virginia. 

Manuscript received for publication 15 October 1986 

USDA Forest Service 

370 Reed Road, Broomall, PA 19008 

May 1987 
Introduction 

Some control of species composition in young hardwood 

stands can be accomplished by releasing trees of desirable 

species and form (Erdmann 1983). Theoretically, released 

trees should grow faster and have a greater chance of 

attaining and maintaining dominance in the new stand. 

Major obstacles in regulating species composition in naturally regenerated stands are the variety of species, stem 

quality, large number of stems, and growth differences 

among species. 

Early work by Trimble (1973, 1974) generally showed that 

7-year-old stems of yellow-poplar, Liriodendron tulipifera L.; 

black cherry, Prunus serotina Ehrh.; and northern red oak, 

Quercus rubra L., did not respond in diameter or height 

growth when all competing trees within a &foot radius of 

the bole were cut. In a 9-year-old stand, Lamson and Smith 

(1 978) measured response of released sugar maple, Acer 

saccharurn Marsh.; red oak; black cherry; and yellowpoplar crop trees. All trees were cut that were one-half or 

more as tall as the crop tree and were within a radius of 5 

feet of the crop tree. Their general conclusions were (1) 

that release did not significantly improve height or diameter 

growth or length of clear stem, and (2) that a large portion 

exhibited crown-class regression in the 5-year period after 

release. One factor affecting response of crop trees in 

these studies, particularly in the 7-year-old stands, was the 

vigorous sprouting from the cut stems surrounding the crop 

tree. 

In this study, we injected glyphosate, a herbicide, into the 

base of competing stems and measured crop-tree response 

in d.b.h. growth, height growth, and changes in crown 

class. Glyphosate injection is very effective in eliminating or 

reducing sprouting of most hardwood species (Wendel and 

Kochenderfer 1982). 

The Study 

Seedling-origin crop trees in three 8- to 12-year-old naturally and artificially regenerated hardwood stands were 

selected for release. Species included codominant and 

intermediate black cherry; codominant, intermediate, and 

suppressed red oak; and intermediate sugar maple (Table 

1). Competing trees were injected with a 20 percent aqueous solution of glyphosate. Injections were spaced at intervals of 1.5 inches edge-to-edge around the base of all 

stems that had a basal diameter larger than 1.0 inch. 

Approximately 1.5 ml of solution was injected into each 

incision. In the 8- and 10-year-old stands, competing trees 

within a radius of 5 feet of the crop tree bole were injected. 

In the 12-year-old stand, competing trees whose crowns 

were touching under or over the crop-tree crown were 

injected (Table 1). All crop trees were permanently marked. 

Crop trees were randomly selected, and every other crop 

tree was released. 

D.b.h., total height and crown class of each crop tree were 

recorded at the time of and 5 years after treatment. Analysis of variance was used to test for differences in d.b.h. 

and height growth. 

Results 

Survival 

Except for codominant black cherry and intermediate sugar 

maple, survival was better for released trees than it was for 

control trees (Table 2). 

Table 1.-Species, number of trees, and type of release used in the study 

Species 

Black cherry 

Black cherry 

Red oak 

Red oak 

Red oak 

Sugar maple 

Initial 

stand 

agea 

8 

8 

10 

10 

10 

12 

Initial 

crown 

Originb classC 

Number of trees 

Control Released 

Type of 

release 

5' radius around bole I, 

,I 

I 

Crown touching 

aptanted seedlings were 1-0 bare-rooted stock. 

bN = natural, P = planted. 

'2 = codominant, 3 = intermediate, 4 = overtopped. 
Table 2.-Five-year height growth and survival of control and released trees 

Initial 

Initial crown Survival Initial height Height-growth of survivors 

Species age classa ' Control Released Control Released Control Released Significanceb 

---Percent--- ---------------Feet --------------- 

Black cherry 8 2 100 92 16.6 16.6 10.8 10.7 NS 

Black cherry 8 3 87 100 14.1 14.3 7.6 7.7 N S 

Red oak 10 2 80 98 14.4 14.8 8.8 8.7 N S 

Red oak 10 3 65 86 13.0 12.3 5.0 6.5 NS 

Red oak 10 4 9 57 10.1 10.9 2.9 3.0 N S 

Sugar maple 12 3 100 100 22.7 24.3 6.5 7.0 NS 

a2 = codominant, 3 = intermediate, 4 =overtopped. 

bNS = not significantly different. Analysis of variance. 

Height growth 

For all species and crown classes, 5-year average height 

growth did not differ significantly between control and 

release trees (Table 2). 

D.b.h. Growth 

Five-year average d.b.h. growth was significantly greater 

for all released trees except 10-year-old overtopped red oak 

(Table 3). However, in all instances 5-year d.b.h. growth 

was nominally greater for released trees than control trees. 

Regardless of crown class, the difference in 5-year d.b.h. 

growth between control and released trees averaged 0.4 

inch for black cherry, 0.3 inch for red oak, and 0.7 inch for 

sugar maple. Also, the 5-year d.b.h. growth for released 

12-year-old intermediate sugar maples was similar to the 

response for codominant 8-year-old black cherry trees. 

Crown-class Changes 

A higher percentage of released than control trees 

remained the same or improved in crown class during the 5 

years (Table 4). A large proportion of black cherry in the 

codominant crown class in both control and released treatments retained their original crown class during the 5 

years. However, of the intermediate black cherry, 57 percent of the control trees retrogressed to the overtopped 

crown class or died. Twenty-four percent of the released 

intermediates became codominants compared to only 4 

percent for the controls. 

A higher percentage of released than control red oaks 

retained their original crown class, regardless of crown 

class. In contrast, there was higher mortality and retrogression to lower crown classes among the control red oak. 

For sugar maples that were initially intermediate, 69 percent of the released trees were codominant 5 years after 

treatment, while none of the control trees moved into the 

codominant class. 

Discussion and Conclusions 

The results of this study have shown that tree injection with 

a 20 percent solution of glyphosate is an effective way to 

eliminate competition around selected crop trees. Earlier 

work by Wendel and Kochenderfer (1982) showed that 

most of the common Appalachian hardwoods were killed 

and did not resprout after 2 years following injection with 

glyphosate. After 5 years in this study, the effects of 

release are still evident. 

In previous early release studies in West Virginia where a 

5-foot release radius was used, 7- and 9-year-old black 

cherry and red oak crop trees did not respond in height or 

diameter growth (Smith 1977). Vigorous sprouts from the 

cut stems were suggested as a possible reason for the 

poor response on the crop trees. In our study, using the 

same release criteria, we found that treated 8-year-old 

black cherry and 10-year-old red oak responded in d.b.h. 

growth and had less crown-class retrogression when a 

herbicide was used to kill competitors. The herbicide application reduced sprouting by killing the competing trees, 

thus leaving the crop trees competition-free for a longer 

period of time. 

Smith (1977) also noted that crop trees in young stands 

were often severely damaged by grapevines that flourished 

following release. 
1 Table 3.-Fiveyear d.b.h. growth of control and released crop trees 

Species 

Initial D.b.h. growth 

Initial crown Initial d.b.h. of survivors 

age classa Control Released Control Releasedb 

Black cherry 

Black cherry 

Red oak 

Red oak 

Red oak , 

Sugar maple 

I a2 = codominant, 3 = intermediate, 4 =overtopped. 

I bNS = not significantly different; * = P(0.05; * * = P(O.O1; analysis of variance. 

I Table 4.-Distribution of control and released trees by crown class, at the end of five growing 

seasons 

Initial Crown class 

Initial crown remained same or improved Dead 

Species age classa Control Released Control Released 

Black cherry 

Black cherry 

Red oak 

Red oak 

Red oak 

Sugar maple 

--------------- Percent --------------- 

8 2 68 88 0 8 

8 3 43 76 13 0 

10 2 14 22 20 2 

10 3 3 48 62 14 

10 4 9 50 9 1 43 

12 3 42 100 0 0 

'2 = codominant, 3 = intermediate, 4 = overtopped 

Since codominant 8-year-old black cherry and 10-year-old 

red oak responded to release, we would recommend 

releasing these. The results of this study also showed that 

some of the intermediate black cherry, sugar maple, and 

red oak responded significantly in diameter growth to 

release. However, 5 years after release only 3 percent of 

intermediate red oak and 24 percent of intermediate black 

cherry were codominant stems. How many of these 

codominant trees will retain this position until final harvest 

is not known. We would recommend releasing some intermediate black cherry where there is a need to improve 

species composition. We would not recommend releasing 

10-year-old intermediate red oak trees. Also, we would 

recommend releasing 12-year-old intermediate sugar 

maple. 

A major advantage of tree injection with glyphosate is that 

sprouting of most hardwood species is reduced, thereby 

providing a longer release period for the crop tree. Injection 

is also a safe and clean method of applying herbicides and 

environmental effects are minimized because the herbicide 

is applied directly to the target species. Cutting of competing trees on the other hand may provide immediate 

release, but sprouting may be a problem later on. For 

release of stump sprout crop trees, however, cutting may 

be the only method that can be used. Also, because cut 

trees are readily visible it may be easier to achieve a 

desired degree of release by cutting. 

Miller (1984) showed that in 12-year-old stands, chain saw 

release cost 42 cents per crop tree, injection with a 20 
percent glyphosate solution cost 61 cents per crop tree, 

and basal spraying with a 4 percent mixture of 2, 4-D and 

fuel oil cost 80 cents per crop tree. However, Miller's study 

did not evaluate the long-term effectiveness of the three 

release methods. In younger hardwood stands, where 

slower growing, desired species may not survive without 

early release, injection of competing stems with herbicide 

might be an effective method for maintaining and increasing growth of selected crop trees. Failure to release certain 

species early may negate future release growth response. 

Our study demonstrated that glyphosate will control many 

hardwood species but that the longer term costleffectiveness compared to other methods has not been determined. 

If species composition is not a concern, we suggest a 

cutting release when trees are more than 25 feet tall (Smith 

1977). Unless circumstances dictate otherwise, crop trees 

of desired species are best picked from the pool of dominant and codominant trees. 

For those who might be interested in using glyphosate to 

release crop trees, we recommend the following: 

Use a 20 percent aqueous solution of glyphosate, 

Inject about 1.5 ml of solution per incision, space incisions at about 1.5 inches edge-to-edge. One incision is 

sufficient for a 1.0-inch d.b.h. tree. 

Inject trees when they are dormant or approaching dormancy, but before sap begins to flow in the spring. 

When the sap is flowing, much of the herbicide solution 

can be forced out of the incision. 

To eliminate a sprout clump, make injections in the 

stump close to the ground. Thus, treatment of individual 

sprouts can usually be avoided. Do not release sprout 

origin crop trees by injecting competing sprouts on the 

same stump. 

Literature Cited 

Erdmann, Gayne G. 1983. Tending valuable young northern and central hardwoods in natural stands. In: Stier, 

Jeffrey C., ed. Proceedings, Silviculture of established 

stands in north central forests: First Society of American 

Foresters Region V Technical Conference; 1983 September 14-16; Duluth, MN. SAF Publ. 83-1 1. Washington, 

DC: Society of American Foresters; p. 76-99. 

Lamson, Neil I.; Smith, H. C. 1978. Response to crop-tree 

release; sugar maple, red oak, black cherry, and 

yellow-poplar saplings in a 9-year-old stand. Res. Pap. 

NE-394. Broomall, PA: U. S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station; 

8 P. 

Miller, Gary W. 1984. Releasing young hardwood crop 

trees-use of a chain saw costs less than herbicides. 

Res. Pap. NE-550. Broomall, PA: U. S. Department of 

Agriculture, Forest Service, Northeastern Forest Experiment Station; 5 p. 

Smith, H. Clay. 1977. Results of precommercial thinning 

in very young Appalachian hardwood stands. Northern 

Logger and Timber Processor 26:24-25. 

Trimble, G. R., Jr. 1973. Response to crop-tree release 

by 7-year-old stems of yellow-poplar and black 

cherry. Res. Pap. NE-253. Broomall, PA: U. S. Depart- I 

ment of Agriculture, Forest Service, Northeastern Forest 

Experiment Station; 10 p. 

Trimble, G. R., Jr. 1974. Response to crop-tree release 

by 7-year-old stems of red maple stump sprouts and 

northern red oak advance reproduction. Res. Pap. 

NE-303. Broomall, PA: U. S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station; 

6 P. 

Wendel, G. W.; Kochenderfer, J. N. 1982. Glyphosate 

controls hardwoods in West Virginia. Res. Pap. 

NE-497. Broomall, PA: U. S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station; 

7 P. 

Caution I 

Pesticides used improperly can be injurious to man, animals, and plants. Follow the directions and heed all precautions on the labels. 

Store pesticides in original containers-out of reach of 

children and pets-and away from foodstuff. 

Apply pesticides selectively and carefully. Do not apply a I 

pesticide when t.here is a danger of drift to other areas. 

Avoid prolonged inhalation of a pesticide spray or dust. 

When applying a pesticide, it is advisable that you be fully 

clothed. 

After handling a pesticide, do not eat, drink, or smoke until 

you have washed. In case a pesticide is swallowed or gets 

in the eyes, follow the first-aid treatment given on the label, 

and get prompt medical attention. If the pesticide is spilled 

on your skin or clothing, remove clothing immediately and 

wash skin thoroughly. 

Dispose of empty pesticide containers by wrapping them in 

several layers of newspaper and placing them in your trash 

can. 
It is difficult to remove all traces of a herbicide (weed killer) NOTE: Registrations of pesticides are under constant 

from equipment. Therefore, to prevent injury to desirable review by the U.S. Department of Agriculture. Use only 

plants do not use the same equipment for insecticides and pesticides that bear the USDA registration number and 1 fungicides that you use for a herbicide. carry directions for home and garden use. 

Wendel, G. W.; Lamson, Neil 1. 1987. Effects of herbicide release on the 

growth of 8- to 12-year-old hardwood trees. NE-RP-598. Broomall, 

PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest 

Experiment Station. 4 p. 

In 8- to 12-year-old Appalachian hardwood stands, crop trees were released 

by stem injecting competing trees with a 20 percent aqueous solution of 

glyphosate. Species released were black cherry, red oak, and sugar maple. 

Release treatments were (a) injection of all trees within a 5-foot radius of 

the crop tree bole and (b) injections of all trees whose crown touched the 

crop tree. Five-year diameter growth of all species was significantly 

increased by both release treatments, but height growth was not affected 

by either treatment. Survival of released crop trees was higher and crownclass retrogression of released trees was less than unreleased trees. 

Glyphosate was effective in controlling most hardwood species during the 5 

years of observation. 

1 ODC 181.41 243.8 176.1 

I Keywords: Appalachian hardwoods, crop trees, release, herbicide 
Headquarters of the Northeastern Forest Experiment Station are in Broomall, Pa. 

Field laboratories are maintained at: 

Amherst, Massachusetts, in cooperation with the University of Massachusetts. 

Berea, Kentucky, in cooperation with Berea College. 

a Burlington, Vermont, in cooperation with the University of Vermont. 

a Delaware, Ohio. 

a Durham, New Hampshire, in cooperation with the University of New Hampshire. 

a Hamden, Connecticut, in cooperation with Yale University. 

a Morgantown, West Virginia, in cooperation with West Virginia University, 

Morgantown. 

a Orono, Maine, in cooperation with the University of Maine, Orono. 

Parsons, West Virginia. 

a Princeton, West Virginia. 

Syracuse, New York, in cooperation with the State University of New York 

College of Environmental Sciences and Forestry at Syracuse University, 

Syracuse. 

a University Park, Pennsylvania, in cooperation with the Pennsylvania State 

University. 

a Warren, Pennsylvania. 

Persons of any race, color, national origin, sex, age, religion, or with any handicapping condition are welcome to use and enjoy all facilities, programs, and servi,ces 

of the USDA. Discrimination in any form is strictly against agency policy, and 

should be reported to the Secretary of Agriculture, Washington, DC 20250. 

I 

*U.S.COVERNRlENT PRINTING OFFICE:1987-748-lJ76:43015