Photographic Guide of 

Selected External Defect 

Indicators and Associated 

Internal Defects 

in Yellow-Poplar 

United States 

Department of 

Agriculture 

Forest Service 

Northeastern Forest 

Experiment Station 

Research Paper NE-646

Everette D. Rast 

John A. Beaton 

David L. Sonderman 
Abstract 

To properly classify or grade logs or trees, one must be able to correctly identify

indicators and assess the effect of the underlying defect on possible end products. 

This guide assists the individual in identifying the surface defect indicator and shows 

the progressive stages of the defect throughout its development for yellowpoplar. 

Twelve types of external defect indicators and associated defects that are particularly 

difficult to evaluate are illustrated and described. 

The Authors 

EVERETTE D. RAST, forest products technologist, received a B.S. degree in forestry

from the University of Missouri in 1960 and an M.S. degree in agricultural economics 

from The Ohio State University in 1970. He joined the USDA Forest Service in 1960 

as a forester on the Mendocino National Forest and transferred to the Northeastern 

Forest Experiment Station, Delaware, Ohio, in 1966. From 1966 to 1987 he was with

the log and tree grade project, and then the management and utilization alternatives 

for nonindustrial private forests. In 1987 he was transferred to the Station's Forestry

Sciences Laboratory in Princeton, West Virginia, as a member of the Advanced 

Hardwood Processing and Technical Resource Center. 

JOHN A. BEATON, forestry technician, received a certificate as a forest technician 

from Lake City Junior College and Forest Ranger School, Lake City, Florida, in 1964. 

He joined the Forest Service in October 1964 as a forestry aid at the Forest Insect 

and Disease Laboratory, Delaware, Ohio. In November 1976, he was transferred to 

Project 1351, Northeastern Forest Experiment Station, Delaware, Ohio, as a forestry

technician. 

DAVID L. SONDERMAN, forest products technologist, joined the Northeastern 

Forest Experiment Station in 1962 and was on the staff of the Eastern Softwood

Timber Quality project until 1972. From 1972 to 1987 he was located at Delaware, 

Ohio, with the Northeastern Station's project on management and utilization 

alternatives for nonindustrial private forests. He is currently with the Station's 

Forestry Sciences Laboratory at Princeton, West Virginia. 

Manuscript received for publication 6 November 1989 

Northeastern Forest Experiment Station 

5 Radnor Corporate Center 

100 Matsonford Road, Suite 200 

P.O. Box 6775 

Radnor, Pennsylvania 19087 

May 1991
Introduction Discussion of Defects

This photographic guide on yellow-poplar is the fifth in a series

designed to assist in the understanding of the relationship 

between exterior defect indicators and the underlying defect. 

In this study, like the black walnut (Rast et al. 1988) and white 

oak (Rast et al. 1989) studies, bolts were sliced and 

photographs of interior defects were taken at the USDA Forest 

Service's Forest Products Laboratory in Madison, Wisconsin. 

In this publication we provide a stereo pair of photographs of

the defect indicators to give the user a more realistic view. 

The defect indicators reported in this publication are: 

suppressed bud; suppressed bud cluster; open and 

occluded (closed) bird peck; light, medium, and heavy

distortions; new and old wounds; seam; bump; and bark 

break. We believe that these indicators often are difficult to 

identify and evaluate in terms of their effect on end-product

quality. Graders normally have little difficulty recognizing and 

evaluating obvious grading defects such as limbs, forks, 

bumps, and butt scars. 

The photo format for each defect evaluated in this publication 

is, first, a pair of stereo photographs of the defect indicator on

the log surface. Next is an enlarged set of prints showing the 

defect indicator followed by a series of prints of the actual 

defect as it appears at different depths below the log surface.

Below the photo of the defect indicator (Fig. 1) is a list that 

describes the size of the defect in terms of length (along the

grain), width (across the grain), and height (above the normal 

bark contour); log diameter, inside the bark (ib) at the defect;

round-up thickness; core diameter; and distance of defect 

above the stump. The information listed below the interior 

defect (Fig. 1) indicates distance below the log surface (inside 

the bark) as well as the distance from the first slice of veneer 

to that particular photographed defect. The last photograph in 

each defect series also lists total veneer thickness, which is

the distance from the initial slice of usable veneer to the 

veneer core. Since the veneer was sliced at 1/16 inch, and 

the depth of the defects is reported in 1/10-inch intervals, 

some of the depth figures may be identical due to rounding.

Procedure

Fifteen yellow-poplar trees on the Vinton Furnace 

Experimental Forest in southeastern Ohio were selected, 

felled, and bucked into twenty-seven 4-foot bolts containing 

the defects selected to be studied. Many of the bolts 

contained two or more defects. The bolts were carefully

transported to a warehouse to be photographed. This 

controlled environment enabled us to take quality

photographs of defect indicators and provided a good 

storage area for the bolts until the film was processed. 

The ends of the bolts were marked off in quadrants using the 

geometric center as the midpoint. The quadrants were aligned 

to keep all of the defects in quadrant 1 or 2, if possible. A 1-

inch groove was routed along the 3-4 quadrant line, providing 

an identification mark in the rotary-cut veneer for clipping. By

clipping at this point, each sheet of veneer was one complete 

revolution of the log. This provided a method for identifying the 

correct defects corresponding to the surface defect indicators

that were photographed. 

Prior to slicing, the bolts were steam-heated in a water vat Suppressed Buds

just enough to loosen the bark. Next, the bolts were debarked 

by hand, replaced in the vats, and heated to the correct 

slicing temperature. A bolt was then removed from the vat, 

chucked in the lathe, and rotary sliced into 1/16-inch-thick 

veneer. Before getting a continuous sheet of veneer, the 

round-up pieces of veneer were counted and those necessary

for photographing were saved. Once it began coming off in a 

continuous sheet, the veneer was clipped at the notch in the 

small end and stacked by bolts. The bolt number was put on 

the first and last sheet of veneer to identify each bolt. Only 10 

to 15 bolts were sliced at a time so the defects could be 

photographed the same day to prevent stain or discoloration. 

Then the veneer was put in cold storage before drying. 

Epicormic branches develop from two types of buds: 

suppressed or dormant buds and adventitious buds 

(Kormanik and Brown 1969 and Shigo 1986). Suppressed 

buds (Fig. 1) can persist for many years as a bud trace or 

they can sprout suddenly after some stimulus such as 

thinning or damage to the tree. After sprouting, many

develop into small limbs that often die, but the bud trace 

usually continues to form in the cambial zone. The defect 

indicator is identified by a slight break in the bark pattern with 

a small protuberance in the center. Adventitious buds form 

anew from the cambium, usually following some injury to the 

tree. 

 1 
Figure 1. - Suppressed bud and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . Depth below - . . . . . . . . 

Log diameter at defect (ib) . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . 

V2 x 1/2 inches 

10.1 inches 

0.3 inch 

5.9 inches 

21.0 feet 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . 0.9 inch 

First sheet of veneer. . . . . . . . . . . . . . . . . . 0.5 inch

 2 
Figure 1 (Continued) 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.4 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 2.0 inches 

Total Veneer Thickness. . . . . . . . . . . . . . . . . . . . 2.0 inches 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.1 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 1.8 inches 

 3 
Suppressed Bud Clusters 

Figure 2 shows very faintly the presence of the concentric 

rings around the defect indicator as well as evidence of 

several individual buds. Also, many adventitious knots are 

visible in the first defect photo.

As its name implies, a suppressed bud cluster is a group of

suppressed buds (3 to 20) tightly clustered in a small area,

normally less than 2 by 2 inches in size. Usually, there is 

evidence of concentric rings around the defect indicator. 

Figure 2.-Suppressed bud cluster and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . . . Depth below

Log diameter at defect (ib). . . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . . 

2 x 2 inches 

14.7 inches 

0.3 inch 

6.0 inches 

31.0 feet 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 inch 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . . . . .0.3 inch 

 4 
Figure 2 (Continued) 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.3 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 2.0 inches 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.3 inch 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . . . . .1.0 inch 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.0 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 3.8 inches 

Total Veneer Thickness. . . . . . . . . . . . . . . . . . . . 3.8 inches 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.3 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 3.0 inches 

 5 
Bird Peck disregarded in grading logs and trees, whether or not they

reach the cambium layer, so long as the tree is cut shortly

after injury. The rationale is that the peck defects will be

removed during the initial stages of primary processing 

(debarking, slabbing. or round-up) of the log. 

Bird peck is evaluated by determining whether callus tissue is 

formed in the peck holes (Rast et al. 1973). If the peck holes

are open, the pecks did not reach the cambium layer and 

there will be no damage. But if the peck holes are closed, 

there will be damage to the tree. Bird pecks are sometimes 

considered as old or new. However, this classification should 

not be used except to say that new bird pecks can be 

Figure 3 shows primarily open bird peck that is not occluded 

and, therefore, can be disregarded. However, careful 

examination of the photograph reveals occluded bird

Figure 3. - Open bird peck. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . . 

Log diameter at defect (ib). . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . 

1 x 13 inches 

8.9 inches 

 0.1 inch 

5.9 inches 

30.0 feet 

 6 
By contrast, in looking at the occluded bird peck in Figure

4 one can observe clearly the callus material in the pecked 

holes and the defects in the underlying wood. Severe bird 

peck can lead to a separation of the wood along the rings. 

pecks (in the center of the row pointed out by the arrows). 

No photos of veneer defects were taken as the only

indication of defects in the wood was these two occluded 

bird pecks. 

Figure 4.- Occluded (closed) bird peck and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . Depth below

Log diameter at defect (ib). . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . 

10 x 10 inches 

10.0 inches 

0.2 inch 

5.9 inches 

28.0 feet 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.0 inch 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . . . . .0.8 inch 

 7 
Figure 4 (Continued) 

Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.1 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 0.9 inch 

Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.2 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 1.0 inch 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.4 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 1.1 inches 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.5 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 1.2 inches 

Total Veneer Thickness. . . . . . . . . . . . . . . . . . . . 1.6 inches 

 8 
Bark Distortions

shows a slight amount of curvature in the surrounding bark 

plates, and the bark pattern varies only slightly from normal.

Because of these features, light bark distortions are 

inconspicuous and often overlooked. Medium bark

Bark distortions usually indicate an overgrown knot and 

because of age they have no height measurement (flush 

with the normal contour of the bark). They are classified as 

light, medium, or heavy. A light bark distortion (Fig. 5)

Figure 5.-Light bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Log diameter at defect (ib). . . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . . 

4 x 3 inches 

15.0 inches 

0.0 inch 

6.0 inches 

27.0 feet 

Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . . . 4.0 inches 

 9 
Figure 5 (Continued) 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.3 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 4.3 inches 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.5 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 4.5 inches 

Total Veneer Thickness. . . . . . . . . . . . . . . . . . . . 4.5 inches 

 10 
of concentric circles encompassing the defect indicator and

"pucker-like" appearance of the center. 

distortions (Fig. 6) show more of the concentric circles, but 

they are broken in several areas by flat bark plates or the 

regular bark pattern. Also, there usually are several welldefined breaks in the bark pattern from the outer edges to the 

center of the defect indicator. Heavy bark distortions (Fig. 

7) normally are identified by the characteristic pattern 

All bark distortions result in some product degrade, but the 

amount of degrade decreases as the depth to the initial 

defect below the log surface increases. Light bark 

Figure 6.-Medium bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Log diameter at defect (ib). . . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . . .

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . . 

2 x 2 inches 

15.4 inches 

0.1 inch 

6.0 inches 

19.0 feet 

Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.1 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 2.0 inches

 11 
Figure 6 (Continued) 

Depth below Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.1 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 3.0 inches

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.4 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 2.3 inches 

distortions, because of their greater depth below the log 

surface, are not considered defects in grading factory lumber 

logs, but medium and heavy distortions are. Likewise, many

of the grading systems for veneer logs disregard light bark 

distortions. If we increase the log diameter at the point of 

occurrence of the light and heavy distortions (Figs. 5 and 7) 

so they are equal to the diameter of the log at the point of 

occurrence of the medium distortion (Fig. 6), then the depth 

below the log surface to the first sign of the defect would be 

approximately 4.2, 2.0. and 0.5 inches, respectively. This 

clear area between the log surface and the defect is 

important in determining product suitability and, therefore, 

the log's economic value. 

Depth below

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.6 inches 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . .. 4.5 inches 

Total Veneer Thickness. . . . . . . . . . . . . . . . . . . . 4.5 inches 

 12 
Figure 7.-Heavy bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size. . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Log diameter at defect (ib). . . . . . . . . . . . . . . . 

Round-up thickness. . . . . . . . . . . . . . . . . . . . . 

Core diameter. . . . . . . . . . . . . . . . . . . . . . . . . 

Defect distance above stump. . . . . . . . . . . . . 

2 x 2 inches Depth below

14.7 inches 

0.3 inch 

5.9 inches 

9.0 feet 

Log surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 inch 

First sheet of veneer. . . . . . . . . . . . . . . . . . . . . . . . . 0.2 inch 

 13