No. 135 

1962 

A WEEDING IN TEN-YEAR-OLD NORTHERN HARDWOODS-METHODS AND TIME REQUIREMENTS 

Although weeding young northern hardwoods is not a common practice. 

most foresters will agree that weeding such stands is silviculturally sound 

in terms of improved growth and quality. Major obstacle to the widespread 

weeding of young stands as a routine cultural treatment is lack of information about the techniques and costs involved. 

As part of an intensive northern hardwood management study at the 

Bartlett Experimental Forest, in Bartlett, New Hampshire, some information on weeding techniques and costs was recently obtained. Data for 

one specific weeding operation are presented here, including the relationship of man-hour requirements to number of .crop trees per acre. and 

observations on crew organization and equipment. 

The Young Stands 

The young sapling stands in which the weeding was done occupied 

small areas, patches of 0.3 to 0.9 acre that had been clearcut 10 years 

before. These patches represented the first cutting in a compartment of 

northern hardwood timber that was to be harvested and regenerated by 

the patch-cutting system. 

The regeneration in patches of this size in the Rartlett area is expected 

to contain a high proportion of yellow and paper birches.' This expecta- 

'See Gilbert, Adrian M , 2nd Jensen, Vlctor S .I MAN~C;ESIENT GUIDE FOR NORTHbRN H4RDW'OODS 

IN NEW ENGLAND U S Forest Serv Northedat Forest E\pt Std , St2 Pdper 112, 22 pp , 11111s , 1958 
tion was realized: both birches were well represented in the 10-year-old 

sapling stands. However, these birches were being badly crowded by other 

species, particularly by the fast-growing noncommercial pin cherry and 

striped maple. Weeding to release the more promising birch stems was 

deemed necessary to maintain them in the stands, as well as to stimulate 

their growth. 

Eighteen patches, having a total area of 11 acres, were weeded in the 

operation described here. Besides yellow birch and paper birch, pin cherry, 

and striped maple, the species present included sugar maple, white ash, 

red maple, and beech. Much of the regeneration was of seed origin, but 

there were occasional sprout clumps of red maple and root suckers of 

beech. The taller stems, from which crop trees were selected for release, 

ranged in height from 15 to 25 feet and in diameter from 1 to 3 inches at 

breast height. 

Both total stocking and the stocking of desirable species varied considerably. Most patches were insufficiently stocked with good stems of 

commercial species to provide the desired number of suitably spaced crop 

trees (about 200 per acre). Some patches had only a few crop trees, and 

were occupied largely by pin cherry, striped maple, and other growth of 

no commercial promise. 

Field Procedures 

All the weeding was done on a crop-tree basis. Species, form, crown 

class, freedom from disease and damage, and origin (seedlings in preference to sprouts) were the major factors considered in choosing the 

individual crop trees (fig. 1). To conform with the objectives of patch 

cutting-that is, to produce new stands containing a high proportion of 

the birches-yellow birch and paper birch were favored over other commercial hardwoods wherever they qualified as good crop trees. In fact, 

most of the crop trees chosen were birches: 60 percent were yellow birch 

and 29 percent paper birch. The rest of the crop trees were sugar maple 

(6 percent), white ash (2 percent), beech (2 percent), and red maple 

(1 percent). A total of 1,305 crop trees were chosen in the 18 patches. 

Crop trees were chosen at a flexible 15 x 15-f00t spacing, which would 

result in about 200 crop trees to the acre if strictly followed. Actually, it 

was possible to adhere to this spacing only in those patches or parts of 

patches that were exceptionally well stocked with good seedling stems 

of commercial species. The actual selections varied by patches from 36 

to 205 crop trees per acre, and averaged 118 trees per acre. 
Figure 1-A typical yellow birch crop tree after weeding. 
The original plan was to remove or kill all trees, regardless of species 

or quality, that were competing directly with the crown of a selected crop 

tree. In practice this was modified, and some competing trees of crop-tree 

caliber were left as insurance. The number of trees removed around each 

crop tree varied little, averaging 4.0 stems per tree. In size, the trees 

removed were comparable to the crop trees-ranging mostly from 15 to 

2 5 feet tall. 

The weeding crew consisted of three men: a forester selected crop 

trees, marked trees to be removed, and kept recards; two laborers cut or 

treated the marked trees. For our modest-size job, this crew organization 

was efficient and quite satisfactory. 

Generally, trees up to 2 inches in diameter at breast height were cut, 

and larger ones were frilled and treated with 2,4,5-T solution. However, 

Figure 2-The Sandvik bush ax was safe to use. It proved 

to be adequate for both frilling, as shown above, and for 

cutting small trees. 
Figure 3-Frilled trees were treated with 2,4,5-T in oil, 

carried in these handy squeeze bottles. Only the larger stems 

and most stump sprouts were frill-treated. 

competing trees that were overtopping or severely rubbing the branches 

of the crop trees usually were cut and pushed to one side. For the whole 

job, 89 percent of the trees removed around crop trees were completely 

severed; only 11 percent were frill-treated with 2,4,5-T. 

The tools used were a 2-pound single-bit ax, a Sandvik bush ax, and a 

plastic squeeze bottle of 2,4,5-T in oil. The two types of axes made a 

good combination for cutting or frilling the sapling-size stems (figs. 2 

and 3). Since the undergrowth in many of the patches was dense, the 

Sandvik tool was especially well adapted for the job; it was not only 

efficient, but also much safer to use than most other cutting tools. For 

severing stems, the Sandvik tool was best suited for those smaller than 3 

inches in diameter; the conventional-type ax was better for larger trees. 

However, for frilling the larger trees, the Sandvik tool worked very well. 
Six of the 18 patches were worked over with no preliminary subdivision 

of the area. The remaining 12 patches were divided into 15-foot lanes in 

advance of tke crew. This was done by one cf the laborers who went 

ahead and marked the lanes with light grocery string. When the stringing 

was finished he ret~lrned to the crew, and the job proceeded as usual. 

Stringing lanes in this manner had advantages: it insured even coverage 

of the area, oriented the crew, and helped guide the spacing of crop trees. 

This was particularly helpful in the denser stands. 

Time Requirements 

Weeding time per acre ranged from 6.0 to 21.6 man-hours, and averaged 

14.5 man-hours, exclusive of travel time to the work area and between 

patches. Several factors influenced weeding time: number of crop trees 

released per acre, steepness of slope, rockiness, amount of underbrush, and 

in some cases problems in selecting the crop trees. Where acceptable crop 

trees either were scarce, or plentiful but unusually uniform in quality, the 

choices sometimes were difficult. 

Of these factors, only number of crop trees released per acre was easily 

measurable. Accordingly, a simple regression equation was developed to 

estimate weeding time, using number of crop trees released per acre as 

the independent variable: 

Y = 4.06 + 0.083X 

where Y is estimated weeding time in man-hours per acre, and X is 

number of crop trees released per acre. The independent variable in this 

equation accounts for 58 percent of the variation in weeding time. The 

standard erior of estimate is i= 3.68 man-hours per acre (fig. 4). Although 

the equation is not precise, it should be helpful for estimating weeding 

time in similar operations. 

Discussion 

If weeding were undertaken on a commercial scale in young stands 

similar to those treated in this study, the man-hour requirements could 

undoubtedly be reduced. For instance, except for occasional rough checks, 

crop-tree tallies would be unnecessary on a production job, and no marking or recording of trees removed would be done. Assuming qualified men 

were available, one technical man could supervise several crews after they 

tiad been trained to select crop trees and perform the requisite weeding 

treatments. 

Our weeding experience to date, as here reported, has provided some 

information on techniques, accomplishments, and man-hour costs that 
30 - 

Sb = 0.19159 

t = 4.5931 (SIGNIFICANT AT 0.01 LEVEL) 

es - T = .76 re = -58 

STANDARD ERROR OF ESTIMATE 23.68 • 

Y = 4.06 +.088X 

Z . 20 

8 

$ 15 

8 P 

$ lo 

5 

. 

0 25 50 75 100 125 150 175 200 225 

CROP TREES RELEASED PER ACRE iXI 

Figure 4-Regression of man-hours on number of crop trees 

released. 

may be helpful to other managers of northern hardwood forests who wish 

to try weeding treatments in their young sapling stands. We cannot as 

yet judge the silvicultural merits of the weeding we have done, but as 

time goes on, the silvicultural effects can be evaluated. These effects will 

give some indication of whether benefits to justify the costs can be 

expected, and also will provide- background information for setting up 

comprehensive, well-designed studies to determine how and when to 

weed, and the cost-and-return relationships. 

-BARTON M. BLUM and STANLEY M. FILIP 

Research Foresters 

Northeastern Forest Experiment Station 

Forest Service, U.S. Dept. Agriculture 

Laconia, N. H.