Some effects of severity of pruning on growth and production in the Concord grape

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UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN

Y

L161— O-1096

Some Effects of Severity of

Pruning on Growth and

Production in the

Concord Grape

By A. S. COLBY AND L. R. TUCKER

UNIVERSITY OF ILLINOIS

AGRICULTURAL EXPERIMENT STATION

BULLETIN 393

CONTENTS

TYPICAL GROWTH AND FRUITING HABITS 179

OUTLINE OF EXPERIMENT 180

SHOOT GROWTH AND FRUIT PRODUCTION 182

PRUNING AND GENERAL VINE GROWTH 189

PRUNING AND VINE YIELD 191

GROWTH AND PRODUCTION RESPONSES 191

GROWTH AND PRODUCTION ALONG THE CANE 194

EFFECTS OF PRUNING ON FRUIT-BUD FORMATION 201

SUMMARY 204

PRACTICAL APPLICATION 204

LITERATURE CITED 206

DEFINITION OF TERMS.. . 206

Urbana, Illinois July, 1933

Publications in the Bulletin series report the results of investigations made

by or sponsored by the Experiment Station

Some Effects of Severity of Pruning on

Growth and Production in the

Concord Grape

By A. S. COLBY, Chief in Small Fruit Culture, and L. R. TUCKER,
formerly Scientific Assistant in Pomology

GRAPEVINE has been subjected to many methods of
I pruning and training by growers and investigators, to all of
"^ which it has adapted itself readily, giving constant and definite
responses. If the grower is to determine the most economical and
profitable degree of pruning to use, he must be able to recognize the re-
sponses which a grapevine makes to different pruning treatments. He
should be able to interpret the condition of a healthy vine by observing
its previous season's growth and fruiting activities, if that season was
normal. He should be able to tell whether a vine has been pruned cor-
rectly, or whether it has been pruned too little or too severely; he
should know what results will be obtained by varying the pruning
treatments.

The investigations reported in this bulletin deal with the cumu-
lative effects on the growth and fruit production of Concord grapes of
consistent winter pruning to varying degrees of severity during the
five years 1924-1928.

TYPICAL GROWTH AND FRUITING HABITS

In any pruning experiment the typical growth and fruiting habits
of the plant must be taken into consideration. As a grape bud de-
velops into a shoot in normal vine growth, a leaf bud is produced at
each node on alternate sides along the shoot. A bud forms in the axil
of each leaf, and sometimes a secondary shoot or lateral is later pro-
duced near this bud. A tendril or a flower cluster may be found opposite
the leaves at some of the basal nodes. After these inflorescences have
been produced up to five in number, the shoot may continue to grow
for several feet with no more blossoms.

The following year the buds vary in size along the portion of the
shoot that was selected as a cane at pruning time. Some do not grow,
but remain latent, while some produce weak and others vigorous shoots.

179

180 BULLETIN No. 393 [July,

Some time during the late summer of the season previous to fruit-
ing, flowers begin to be differentiated in the fruit bud in the axil of
the leaf on the shoot.6* The number of these inflorescences in the
different buds along the shoot varies, fewer being found near the base
than farther out. This habit has been widely studied, usually by meas-
uring the fruit production the following year on the shoots originating
from these buds.2> 7> 8> 9> "» 14* These studies, indicating that the basal
buds are less fruitful than the buds farther from the base, resulted in
the recommendation of the so-called "long-cane" system of pruning
(leaving canes with five or more nodes each) rather than the "spur"
system (leaving approximately three nodes per cane). Again, buds on
some shoots contain more flower clusters than those on other shoots.
A study of this variation has shown that the shoot of medium vigor
will make the most productive cane the following year.10' "*

When a bud contains more than one flower cluster, the clusters
usually vary progressively in size along the fruiting area of the shoot
produced from this bud, the tip cluster being the smallest.4* This in-
dicates that the clusters nearer the base in the fruit bud increase in
size as extra clusters are set, and that the buds carrying the largest
number of inflorescences are potential producers of large clusters.

OUTLINE OF EXPERIMENT

In the experiment reported in this bulletin the 4-cane Kniffin sys-
tem of training was followed. Data were secured from 48 vines in
1927 and from 64 in 1928. The plants used in the experiment are
growing in the Station vineyard in Urbana. They were planted in
1917 and are of average size for their age in that locality.

The vineyard is located on the eastern slope of a recessional mo-
raine characteristic of the Early Wisconsin glaciation. The soil is
brown silt loam of morainal type merging into a black clay area at the
base of the slope. The vines are so distributed over the plot that soil
differences are minimized. Clean cultivation is practiced during the
early part of the growing season, followed by a cover crop of oats,
buckwheat, and soybeans sown in August and disked under the fol-
lowing spring.

The number of nodes to which any vine in this experiment was
pruned varied not more than 15 in any two of the six years 1922-1927.
In 1922 the vines were classified into seven groups according to degree

*These numbers thruout the text refer to literature citations on page 206.

1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

181

of severity of pruning, the number of nodes that were left in the re-
spective groups ranging from 20 to 90 in multiples of 10.* This treat-
ment was consistently followed for five years and detailed comparisons
made of vine growth and production in 1927 at harvest time. The
treatment was continued and comparisons again made in 1928.

TABLE 1. — SUMMARY OF GROWTH AND PRODUCTION OF CONCORD VINES,
ILLINOIS EXPERIMENTS, 1927 AND 1928

Item

Year

Node-number range to which vines were pruned

Total

20-29

30-39

40-49

50-59

60-69

70-79

80-89

1

Number of vines in
each range

1927
1928

7
9

3

24

15
17

11
11

9
3

2
0

1
0

48
64

Vine averages

2

Average number of

1927

17.6

30.3

37.7

47.5

54.6

61.5

65

shoots produced

1928

17.1

25.8

35.2

43.1

50.3

per vine

3

Percentage of nodes

1927

29

19

26

27

21

29

28

dormant

1928

28

28

26

24

23

4

Percentage of nodes

1927

8

15

12

15

11

16

8

producing two

1928

8

11

11

8

10

shoots

5

Percentage of

1927

15

8

5

3

2

1

2

shoots broken off

1928

16

12

8

5

6

6

Total growth of

1927

130

166

200

226

233

241

264

main (primary)

1928

144

183

204

205

233

shoots in feet

7

Total growth of lat-

1927

92

56

91

90

78

95

64

eral (secondary)

1928

168

150

140

88

100

shoots in feet per

vine

8

Total growth of

1927

223

223

291

316

310

336

327

main and lateral

1928

312

333

344

293

334

shoots in feet per

vine

9

Number of laterals

1927

61

83

99

111

122

156

146

per vine

1928

109

124

138

114

155

10

Total number of

1927

13

53

60

74

90

96

96

clusters per vine

1928

18

35

54

63

78

11

Average weight of

1927

19.9

122.8

173.1

198.6

250.6

247.0

275.0

fruit per vine in

1928

48.1

99.7

135.2

167.3

211.5

ounces

12

Average size of

1927

1.36

2.35

2.66

2.64

2.70

2.46

2.86

cluster in ounces

1928

2.22

2.66

2.48

2.59

2.68

1 3

Number of spur

1927

4.0

7.7

12.9

17.0

19.8

24.0

45.0

buds left per vine

1928

4.3

8.1

10.7

18.8

22.3

(Table is concluded on next page.)

*The small buds at the base of the cane were included in making the counts.
These buds are dormant or produce a nonfruitful shoot.** In this experiment
both fruitful and nonfruitful shoots were considered.

182

BULLETIN No. 393
TABLE 1. — Concluded

[July,

Item

Year

Node-number range to which vines were pruned

20-29

30-39

40-49

50-59

60-69

70-79

80-89

Shoot averages

14

Average length of

1927

88

67

66

59

51

48

49

main shoot in

1928

102

89

70

59

56

inches per vine

15

Average length of

1927

63

22

33

24

17

20

12

the laterals in

1928

123

80

49

26

24

inches from each

main shoot

16

Average length per

1927

151

89

99

82

68

68

60

shoot in inches of

1928

225

169

119

85

79

terminals and

laterals combined

17

Average number of

1927

3.4

2.8

2.8

2.4

2.3

2.6

2.2

laterals from each

1928

6.6

5.2

4.0

2.8

3.1

main shoot

18

Average number of

1927

.66

1.73

1.53

1.59

1.65

1.56

1.48

clusters per shoot

1928

1.02

1.34

1.54

1.47

1.55

19

Average weight of

1927

1.0

4.1

4.4

4.3

4.6

3.9

4.2

fruit in ounces

1928

2.7

3.8

3.8

3.9

4.2

per shoot

Growth and fruit production were studied both separately and col-
lectively in each pruning group, both the shoots and the cane being
used as units of comparison. The location and length of each main
shoot on the vine, the number and length of its laterals, and the number
and weight of clusters produced were noted. From these data the
effects of pruning to varying degrees of severity were determined.

SHOOT GROWTH AND FRUIT PRODUCTION

Growth. — The 48 vines from which data were secured in 1927,
ranging from the 20-to-29-node to the 80-to-89-node group (Table 1,
Item 1) produced 2,003 shoots ranging in length from less than 1 foot
to more than 50 feet per shoot (Table 2). The 64 vines in the 1928
test ranging up to the 60-to-69 node group (Table 1, Item 1) pro-
duced 1,995 shoots. The shoot growth per bud in this group varied in
length from less than 1 foot up to 100 feet (Table 2).

The shoots were first grouped according to length of terminals and
laterals (Table 2). About half the shoots were less than 5 feet long.
The short ones had very few and short laterals. The more vigorous
shoots were longer wTith an increase in both length and number of

1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

183

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BULLETIN No. 393

[July,

laterals (Fig. 1). Lateral shoot growth occurred, therefore, at a more
rapid rate than growth of the central or main shoot. Since the laterals
produce many of the leaves, a larger proportion of the leaf surface
on the very vigorous shoots must have been formed later in the season
than on the less vigorous shoots. Both the very weak and the very

800

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300

200

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• LATERAL LENGTH 1926

TERMINAL LENGTH 1928

H ll 1927

200

300 400 500 600 700
TOTAL SHOOT GROWTH IN INCHES

900 1000

FIG. 1. — RELATIONSHIP BETWEEN LENGTH OF TERMINALS AND OF LATERALS
ON SHOOTS OF DIFFERENT DEGREES OF VIGOR, 1927 AND 1928

An increase in shoot vigor resulted in an increase in both length and number
of laterals.

vigorous shoots produced slightly fewer clusters and slightly less fruit
than did the shoots of medium vigor (Table 2). Similar and less vari-
able results were previously reported by the authors.4*

The variation in vigor and fruitfulness between groups was so
slight and the variation within each group was so large, as shown by
standard deviations in Table 2, that there seemed to be little relation-
ship in these shoots between vigor and fruit-bud formation or fruit
production.

Clusters. — The shoots were also classified according to the number
of clusters they produced (Table 3). The number of clusters per shoot
during the years 1927 and 1928 ranged from 0 to 5 and 0 to 4 re-

1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

185

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7P27
Number of shoots in each cl

Average ounces of fruit per
Standard deviation in ounce

Average weight per cluster i

Average terminal length per
Standard deviation in inches

Average lateral length per si
Standard deviation in inches

Average combined termina
per shoot in inches
Standard deviation in inches

Average number of laterals
Average length per lateral ii

192S
Number of shoots in each cl

Average ounces of fruit per
Standard deviation in ounce

Average weight per cluster i

Average terminal length per
Standard deviation in inche

Average lateral length per s
Standard deviation in inche

Average combined termina
per shoot in inches. . . .
Standard deviation in inche

Average number of laterals
Average length per lateral ii

186

BULLETIN No. 393

[July,

spectively (Table 3), while the amount of fruit on a shoot ranged from
none to more than a pound. Since this number had been determined
in the flower bud, this grouping was used as an index to the amount
of flower formation that took place. The number of clusters was also
a very good index of the amount of fruit produced (Tables 2, 3,
and 4). Even under the wide range of pruning treatments for the

FIG. 2. — CONCORD VINE SEVERELY PRUNED TO 16-25 NODES, 1924-1929

Severe pruning of the above vine for six years resulted in too vigorous
shoots with long internodes. Very little fruit was in prospect from this vine for
the 1929 season. (Photographed June 5, 1929)

two years, 1927 and 1928, the production of any of the growing buds
left on the vines after pruning seemed to be largely determined by the
number of embryonic flowers differentiated the previous season.

In accordance with the findings of Partridge,10* Schrader,12* and
the authors,4* the average cluster size in a given area became larger
as the number of clusters increased (Table 3).

As shown by the standard deviations, a wide range of shoot vigor
existed among those shoots having the same number of clusters

1933}

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

187

(Table 3). There seemed to be little relationship between shoot vigor
and the previous year's fruit-bud formation, tho the extent of fruit-bud
formation appeared to have considerable effect upon the production of
a shoot the following year.

FIG. 3. — CANE FROM CONCORD VINE PRUNED TO 16-25 NODES, 1924-1928

Vigorous shoots with considerable lateral growth, much of which occurred
late in the season, developed on this severely pruned cane. One shoot has been
broken off near the end of the old cane.

Yield. — The shoots were again classified and studied according to
the number of ounces of fruit they produced (Table 4). Under this
method of grouping, average growth was similar to that shown in
Table 3, where the number of clusters was taken as the unit. Under

188

BULLETIN No. 393

[July,

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1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

189

this range of consistent annual pruning, individual shoot vigor had very
little apparent effect on the same year's fruit production.

PRUNING AND GENERAL VINE GROWTH

The growth and fruiting activities of the different groups of vines
varied with the treatments they received (Table 1 and Figs. 2, 4, and
6). The number of shoots was limited in proportion to the number

FIG. 4. — CONCORD VINE PRUNED TO APPROXIMATELY 60 NODES DURING 1924-1929

Moderate pruning of the vine as shown above resulted in shoots of medium
vigor and with sufficient bloom to yield a good crop. (Photographed June 5,
1929)

of buds left at pruning time (Table 1, Item 2). This limitation, how-
ever, did not seem to affect markedly either the percentage of nodes
producing two shoots (Item 4) or the percentage of nodes remaining
dormant (Item 3).

At harvest time a survey of the activity of these vines showed that
the amount of their new wood or shoot growth was not limited by the
severity of the pruning treatment (Item 9). Even where the more se-
vere pruning reduced the number of buds and thus limited the possible
number of potential shoots, each shoot was usually longer than the
shoots on vines less severely pruned (Item 7) and produced more
laterals of greater vigor (Item 15). As a result the total vegetative
growth of the vine remained about constant even tho the type of
growth varied.

190

BULLETIN No. 393

[July,

Two other conditions resulting from the pruning need to be taken
into account in this connection. First, more severe pruning resulted in
an increase in the percentage of shoots broken by various causes, such
as storms and tools used in cultivation (Item 5). This may be ex-
plained by the fact that the smaller number of shoots afforded less

FIG. 5. — CANE FROM CONCORD VINE PRUNED TO 56-65 NODES, 1924-1928

Shoots of medium vigor with few laterals resulted on this moderately
pruned cane. Compare with the too vigorous shoots resulting from severe prun-
ing as shown in Fig. 2. Polarity along the cane is illustrated by the shoot
growth.

protection to one another while the resulting vigorous and tender
growth offered a greater exposure. Next, the 4-cane Kniffin system of
training, as previously mentioned, theoretically involves leaving four
spurs at pruning time for renewal purposes. With the vines in the very
severely pruned group, spurs were often unattainable in the desired

1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

191

location (close in to the trunk). The severely pruned canes were short
and in some cases behaved similarly to spurs in that they furnished
some of the shoots for canes the following year. On the other hand,
where the very light pruning (Item 13) was followed consistently, it
was often impossible, at pruning time, to find four canes long enough
to furnish the required number of buds, and a few extra spurs were
necessarily left on the vine.

PRUNING AND VINE YIELD

The average yield per vine in the different groups declined as the
severity of pruning was increased (Table 1, Item 11). Since pruning
has long been practiced as a method of thinning the fruit of the grape,
this result was expected.

The average production per shoot was also slightly smaller with
this decreased total yield (Item 19). Shoot production was determined
by size and number of clusters (Items 12, 18), both of which varied in
a more or less similar manner.

GROWTH AND PRODUCTION RESPONSES

Effects of Cane Length on Shoot Growth and Fruit Production of
Vines Similarly Pruned. — Grape production is related to the fruiting
pattern of individual canes, as previously discussed. In this experi-
ment the cane length of the vines, which were trained to the 4-cane
Knirnn system, necessarily varied under the different pruning treat-

TABLE 5. — AVERAGE GROWTH AND FRUIT PRODUCTION PER SHOOT FROM CANES

PRUNED TO DIFFERENT NUMBERS OF NODES AND ORIGINATING FROM

VINES PRUNED TO A SIMILAR NUMBER OF NODES

Number of nodes
per cane left
after pruning

Termi-
nal
length

Lateral
length

Total
length

Number
of
clusters

Weight
of
fruit

Size
of

clusters

Nodes
forming
shoots

inches

inches

inches

OS.

02.

perct.

Vines with 40 to 49 nodes (1927)

Canes with 1 to 8 nodes

68

29

98

1.81

5.18

2.86

69

Canes with 9 to 16 nodes

66

30

97

1.88

5.96

3.17

79

Increase due to extra cane length

-2

+ 1

-1

+ .07

+ .78

+ .31

+10

Vines with 40 to 49 nodes (1928)

Canes with 1 to 8 nodes

78

63

141

1.68

4.20

2.50

72

Canes with 9 to 16 nodes

68

41

108

1.87

4.80

2.56

78

Increase due to extra cane length

-10

-22

-33

+ .19

+ .60

+ .06

+6

Vines with 50 to 59 nodes (1928)
Canes with 1 to 8 nodes

53

26

79

1.57

4.13

2.63

70

Canes with 9 to 16 nodes

65

30

95

1.92

5.45

2.84

81

I ncrease due to extra cane length

+ 12

+4

+16

+ .35

+ .32

+ .21

+11

192

BULLETIN No. 393

[July,

ments. The effects of pruning on yield may be studied thru the activi-
ties of the canes as well as thru those of the vine.

To determine the effect of cane length upon growth and produc-
tion, all of the canes in one group of vines were divided according
to their length, as shown in Table 5. This treatment was repeated
with three groups in order to obtain three measures of the average
variations. The canes with nine or more nodes formed a noticeably
larger number of shoots per node than did those with fewer nodes.

TABLE 6. — EFFECT OF DEGREE OF SEVERITY OF PRUNING ON GROWTH AND FRUIT
PRODUCTION PER SHOOT FROM CANES WITH SIMILAR NUMBERS OF NODES

Number of nodes
per cane left
after pruning

Termi-
nal
length

Lateral
length

Total
length

Number
of
clusters

Weight
of
fruit

Size
of
clusters

Nodes
forming
shoots

Canes with 5 to 8 nodes on vines
pruned to —
(1927)

inches
80

inches
48

inches
128

1.33

OS.

3.26

OS.

2 45

percl.
71

45 nodes or more

60

26

86

1.80

4.74

2 63

71

(1928)

91

88

180

1.60

5.18

3.24

71

40 nodes or more

70

52

122

1.66

4.15

2.50

72

Canes with 9 to 12 nodes on vines
pruned to —
(1927)
49 nodes or less

68

30

99

1.86

5.94

3.20

77

50 to 59 nodes

60

23

82

1.83

5.20

2.85

75

55

17

72

1 83

5 24

2 85

84

(1928)
39 nodes or less

95

74

170

1.63

4.42

2.71

79

40 to 49 nodes

70

44

114

1 85

4 84

2 61

72

50 nodes or more

68

34

102

1.85

5.27

2.85

77

The average productivity of these shoots was also greater in both
number and size of clusters. The shoots consisted of about the same
length terminals and laterals in each cane class. The variations in yield
in the 9-to-16-node section were actually larger than they appear at
first glance, since the average is taken on all shoots of the cane and
not on the shoots of this area alone.

It is concluded, therefore, that increased length of cane increased
the average yield per shoot, but did not affect shoot vigor.

Effects of Severity of Vine Pruning -on Shoot Growth and Fruit
Production of Canes With Similar Node Numbers. — The effects of
severity of vine pruning upon growth and production of buds on canes
with similar bud numbers were next determined (Table 6). The num-
ber of buds forming shoots did not vary consistently with the differ-
ent pruning treatments, nor was there a consistent variation in the
average yield per shoot. As the severity of pruning was increased,

1933] GROWTH AND PRODUCTION IN THE CONCORD GRAPE 193

growth and production of the remaining buds were affected in the
following manner: Shoot growth consistently increased with a pro-
portionately wider variation in length of laterals than of terminals.
Production was not markedly affected within the divisions made.

Growth and Production Relationships. — Results of the experiment
having indicated that shoot vigor is determined by the severity of
winter pruning and production by the number of nodes left and by the
number of flowers formed in the buds the previous season, an effort
was next made to determine if any correlation exists between produc-
tion, number of clusters, and growth on like portions of canes similarly
pruned. Shoots grown in 1927 from the fifth to the eighth node on
canes 9 to 12 nodes long on vines pruned to 49 to 63 nodes were
studied. This was the closest selection possible if a dependable number
of shoots was to be retained.

A study of these selected shoots is summarized in Table 7. A cor-
relation of -f- .319 rh .043 was found to exist between terminal shoot

TABLE 7. — RELATIONSHIP BETWEEN GROWTH AND FRUITING OF SHOOTS FROM STH TO

STH NODES ON CANES 9 TO 12 NODES LONG ON VINES PRUNED TO

49 TO 63 NODES, 1927

Correlation between number of clusters and —

+ .778

±

.019

Terminal length per shoot

4- .351

-

.042

Lateral length per shoot

+ .142

-

.047

Combined terminal and lateral length per shoot

+ .275

-

.044

Correlation between ounces of fruit and —

-

.043

Lateral length per shoot

+ .142

~

.047

Combined terminal and lateral length per shoot

-

.046

length and ounces of fruit. Since the correlation between length of
laterals and production was still lower, altho positive ( -f- .142 ± .047),
it seems unlikely that the same year's growth and production have
much in common. A correlation of -(- .351 ± .042, which is fully as
high as the one just mentioned, between number of clusters and termi-
nal shoot length indicates that the relationship that does exist may
continue from the earlier existing relationship between fruit-bud for-
mation and bud vigor. This is further substantiated by the much higher
correlation of + .778 ± .019 between number of clusters and yield.
The relationship resulting between shoot vigor and fruit-bud forma-
tion as measured by number of clusters is related to parallel patterns
of activity along the cane. These patterns appear in the section on
growth and production along the cane, page 194 to 201.

194 BULLETIN No. 393 [July,

To check still further the relationship between fruiting and growth
the same summer (1928), the factor of vigor as it affects fruit-bud
formation was eliminated as much as possible by selecting shoots with
two clusters. The effect of vigor as induced by pruning was also
largely nullified by choosing shoots with the same range in primary
length (80 to 99 inches). The weight of fruit on these shoots with
similar fruit-bud formation and similar vigor at pruning time was cor-
related with lateral length in inches. The variation in lateral growth
as measured by the standard deviation was 45.4 inches, and in produc-
tion was 2.4 ounces. These variations were larger than the limitations
placed on terminal growth and number of clusters. After thus limiting
the factors of fruit-bud formation and early vigor, a correlation of
no significance ( -f- .096 ± .076) was found between fruit development
and lateral growth during the summer. This correlation indicates that
under the conditions existing in this experiment the amount of fruit
normally produced by a shoot seems to have little or no effect on
growth. Since this is a shoot study, it does not take into account the
effect of production by one shoot on the growth of another, which may
partially explain why these data appear to disagree with those of
Chandler and Heinicke,1* who found that fruit production decreased
top growth on the vine as a whole.

In order to measure the relationship between fruit-bud formation
and the vigor of the buds the following spring, one vine (Fig. 6)
was left unpruned in 1929 and at blooming time, June 5, the number
of flower clusters present and the vigor in terms of shoot length
were determined. Since the vine was left unpruned in 1929, the in-
dividual buds were expected to show the same relative vigor as they
had the previous season. The correlation between fruit-bud formation
and growth at blooming time was + -444 ± .026. This is similar to the
correlation found by Schrader13* between shoot length on May 22 and
size of bunch on shoots that were thinned to one cluster before set-
ting. The correlation was, however, slightly higher than that of termi-
nal growth and fruiting, as previously presented, and shows that the
relationship between growth and fruiting is one of bud vigor and
fruit-bud formation continuing on to fruit development.

GROWTH AND PRODUCTION ALONG THE CANE

Vines trained to the 4-cane Kniffin system and pruned to different
degrees of severity would, judging from the above data, be expected to
vary in cane length somewhat proportionately to the severity of prun-

1933}

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

195

ing. The distribution of the 199 canes left on the 48 vines in 1927 and
the 225 canes of 1928, according to length in number of nodes and
pruning treatment of the vine supporting them, is shown in Table 8.
The average activity of the different length canes proved to be directly

FIG. 6. — CONCORD VINE MODERATELY PRUNED TO 50 NODES IN 1928,
WITH No PRUNING IN 1929

A large number of weak shoots beginning growth with too many fruit
clusters resulted from moderate pruning in 1928 and no pruning in 1929.
(Photographed June 5, 1929)

related to the pruning range followed the preceding winter and also,
altho to a less extent, of the winter before that.

Shoot Growth Along the Cane. — The number of shoots produced
per node along the cane was larger as more nodes were left on the
cane and vine at pruning time (Table 9). Examination of the canes
from base to tip indicated that this growth pattern was due primarily
to greater activity of buds on more distal nodes in starting shoots.

The average vigor of shoots or growth per bud as measured by
length of terminals (Table 10) and of laterals (Table 11) decreased
with length of cane. The growth of laterals diminished more rapidly
than that of terminals, as would be expected from the conclusions
drawn from the data in Table 6 (page 192).

196

BULLETIN No. 393

[July,

TABLE 8. — DISTRIBUTION OF CANES ACCORDING TO NUMBER OF NODES TO WHICH
VINES WERE PRUNED AND ACCORDING TO NODES PER CANE

Nodes per vine

Nodes per cane

All
canes

1-4

5-8

9-12

13-16

Number of canes in each group, 1927

20-29

3
3
3
2
2
5
0

18
51.2

23
6
31
13
9
1
1

84
42.8

0
3
25
24
20
4
2

78
54.9

0
0
3
6

7
2

1

19
60.3

26
12
62
45
38
12
4

199

30-39

40-49

50-59

60-69

70-79

80-89

Number of canes in each group, 1928

20-29

10

4
1
2
0

17
31.6

22
77
35
17
4

155
38.3

2
15
31
21
6

75
46.4

0
0

2
4
2

8
54.5

34
96
69

44
12

255

30-39

40-49

50-59

60-69

Total number of canes

Average nodes per vine

TABLE 9. — AVERAGE NUMBER OF SHOOTS PER NODE IN CANE SECTIONS PRUNED TO
DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th

nodes

9th-12th
nodes

13th-16th
nodes

Number of shoots per node, 1927

1-4

.71
.56
.60

.54

.58

1.03
1.08
1.00

1.04

i.'ii

1.19

1.15

1.36
1.36

.71
.74
.91
.97

.86

5-8

9-12

13-16

Average for all canes

Number of shoots per node, 1928

1-4. . .

.66
.54
.51

.62

.54

.96
.97
.91

.96

i!oo

1.15

i!66

1.00

.66

.71
.82
.87

.76

5-8

9-12

13-16

Average for all canes

1933}

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

197

TABLE 10. — AVERAGE TERMINAL GROWTH PER SHOOT IN CANE SECTIONS PRUNED TO

DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th
nodes

13th-16th
nodes

Terminal growth per shoot, 1927

1-4

inches
65

inches

inches

inches

inches
65

5-8

65

74

70

9-12

51

60

70

61

13-16

42

52

59

71

56

Average for all canes

57

64

67

71

63

Terminal growth per shoot, 1928

1-4

86

86

5-8

82

84

83

9-12

65

72

88

75

13-16

36

36

50

59

45

Average for all canes

76

77

82

59

77

TABLE 11. — AVERAGE LATERAL GROWTH PER SHOOT IN CANE SECTIONS PRUNED TO

DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th
nodes

13th-16th
nodes

Lateral growth per shoot, 1927

1-4

inches
37

inches

inches

inches

inches
37

5-8

30

42

36

9-12

18

19

34

23

13-16

15

20

21

43

24

Average for all canes

14

27

34

43

28

Lateral growth per shoot, 1928

1-4

106

106

5-8

69

77

73

9-12

39

44

58

46

13-16

6

6

7

14

8

61

60

50

14

59

198 BULLETIN No. 393 [July,

Both terminal and lateral shoots from each group of canes were
shortest at the base of the cane and increased in length as they origi-
nated nearer the tip. Apparently the shoot- vigor pattern of a vigorous
cane, like its productiveness, tends to increase with the buds farther
out from the base to at least the sixteenth node. This probably ex-
plains most of the correlation found between shoot growth and produc-

FIG. 7. — FLOWERING SHOOTS FROM A HEAVILY PRUNED, A MODERATELY PRUNED,
AND AN UNPRUNED CONCORD VINE

The vine pruned severely to 16-25 nodes (1) shows a more vigorous growth
than the vine pruned moderately to 56-65 nodes (2). The vines that received no
pruning (3) was much less vigorous than either of the pruned vines.

tion (Table 7). As pruning treatments become more severe and shorten
the cane accordingly, they also increase the vigor of the remaining
buds nearer the base (Figs. 3 and 5).

Production Along the Cane. — In some of the earlier studies on
cane production the node was used as a unit instead of the shoot,
which is usually considered as the unit in this study. The node is used
as a unit in Tables 12 and 13, in which production results are shown.

In general, the findings in this experiment confirm duplicate studies
in other states. That is, they show that the production per shoot tended
to be low at the base of the cane and increased to about the ninth to
sixteenth nodes (Table 15), and that the production per node varied
in the same direction, altho more widely, owing to the differences in
number of shoots produced at the various nodes (Table 16). This
variation in the production of the different areas of the cane in the

1933}

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

199

TABLE 12. — AVERAGE NUMBER OF CLUSTERS PER SHOOT IN CANE SECTIONS
PRUNED TO DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th
nodes

13th-16th
nodes

Number of clusters per shoot, 1927

1-4

1.31
1.59
1.75
2.03

1.67

1.55
1.98
1.96

1.83

1.70
2.09

1.81

2.' 07

2.07

1
1
1
2

1

31
.57
84
04

74

5-8. . .

9-12

13-16

Number of clusters per shoot, 1928

1-4

.63
1.50
1.66
2.00

1.50

1.73
1.91
2.17

1.82

l!74
2.25

1.82

2.35
2.35

1

1

2

1

63
62
80
19

71

5-8

9-12

13-16

Average for all canes

TABLE 13. — AVERAGE NUMBER OF CLUSTERS PER NODE IN CANE SECTIONS

PRUNED TO DIFFERENT NODE NUMBERS

(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

lst-4th
nodes

5th-8th
nodes

9th-12th

nodes

13th-16th
nodes

Average for
all sections

Number of clusters per node, 1927

1-4..
5-8..
9-12.
13-16.

Average for all canes .

.93

.89

1.05

1.10

.98

1.60
2.14
1.96

1.90

1.94
2.50

2.90

2.82
2.82

.93
1.17
1.68
1.98

1.53

Number of clusters per node, 1928

1-4. . .

.42

.42

5-8

.82

1.66

1.15.

9-12

.84

1.85

2.06

1.48

13-16

1.25

1.97

2.25

2.35

1.90

.81

1.75

2.10

2.35

1.30

200

BULLETIN No. 393

[July,

TABLE 14. — AVERAGE WEIGHT OF FRUIT PER CLUSTER IN CANE SECTIONS

PRUNED TO DIFFERENT NODE NUMBERS

(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th
nodes

13th-16th
nodes

Weight of fruit per cluster, 1927

1-4

oz.
2.64
2.36
2.65
2.92

2.57

oz.

2'.73
3.18
3.31

3.06

oz.

2.88
2.89

2.88

oz.

i!68
2.68

oz.
2.64
2.56
2.97
2.97

2.86

5-8

9-12

13-16.

Weight of fruit per cluster, 1928

1-4

2.62
2.54
2.23
2.08

2.50

2.91
2.91
2.87

2.91

2. 'SO
3.14

2.87

2^46
2.46

2.62
2.75
2.72
2.74

2.70

5-8

9-12

13-16

TABLE 15. — AVERAGE WEIGHT OF FRUIT PER SHOOT IN CANE SECTIONS PRUNED TO
DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th
nodes

13th-16th
nodes

Weight of fruit per shoot, 1927

1-4

oz.
3.45
3.76
4.65
5.91

4.51

oz.

i'.23
6.31
6.48

5.60

oz.

4.91
6.05

5.22

oz.

s!s3

5.53

oz.
3.45
4.02
5.48
6.06

5.18

5-8

9-12

13-16. .

Weight of fruit per shoot, 1928

1-4

1.66

3.80
3.72
4.15

3.74

5.04
5.57
6.23

5.30

4.87
7.07

5.23

S. 79
5.79

1.66
4.46
4.91
6.00

4.71

5-8

9-12. .

13-16

Average for all canes .

1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

201

TABLE 16. — AVERAGE WEIGHT OF FRUIT PER NODE IN CANE SECTIONS PRUNED TO

DIFFERENT NODE NUMBERS
(Data for same canes as in Table 8)

Number of nodes
per cane left
after pruning

Section of cane from base to tip

Average for
all sections

lst-4th
nodes

5th-8th
nodes

9th-12th

nodes

13th-16th
nodes

Weight of fruit per node, 1927

1-4... .

01.

2.46

ot.

oz.

oz.

oz.
2.46

5-8

2 09

4 35

2 99

9-12

3 79

6 81

5 58

4 99

15-16

3.20

6.48

7.22

7.54

5.89

Average for all canes

2 64

5 90

6 02

7.54

4 45

Weight of fruit per node, 1928

1-4

1.10

1.10

5-8

2 07

4 82

3 16

9-12

1.88

5 38

5 78

4 04

13-16

2.59

5 64

7 07

5.79

5.20

Average for all canes

2 03

5 09

6 02

5 79

3 58

Illinois studies, as in those in other states, was determined largely by
the number of clusters produced but was also somewhat affected by
the size of the clusters.

EFFECTS OF PRUNING ON FRUIT-BUD FORMATION

The data in Tables 12 and 14 show that the shoots on each section
of the short canes consistently produced both fewer and smaller
clusters than did the shoots on the same regions of the longer canes.
These data include a larger range of variables in vine pruning than
do the data in Tables 5 and 6, where this variation does not show con-
sistently.

Keeping in mind that the severity of pruning within the limits of
this experiment did not affect the current year's cluster production of
the buds left, and that the ability of a bud to produce was determined
largely at the time of fruit-bud formation, the authors began studies to
determine the effects of the severity of pruning on fruit-bud formation.

The number of clusters produced by a shoot during the growing
season was considered an index of the ability of the bud to form in-
florescences, since practically no aborted flowers were noted. Any
discrepancy caused by the polarity of cane activity was overcome by

202

BULLETIN No. 393

[July,

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1933]

GROWTH AND PRODUCTION IN THE CONCORD GRAPE

203

numbering all nodes progressively outward, starting with the basal
node at the trunk. The clusters on the shoots from each two nodes
of all canes of the vines in each group were averaged separately, as
shown in Table 17. The averages of the shoots in the first four groups,
including those from the first eight nodes, were then averaged as an

20-29

30-39

40-49

50-59

60-69

70-79

BUDS PER VINE
FIG. 8. — EFFECTS OF PRUNING ON FRUIT-BUD FORMATION

The rate of fruit-bud formation per node was low when severe pruning was
practiced and increased with the decrease in severity of pruning up to 56-65
nodes.

index of fruit-bud formation. Data for the other nodes were listed
but not averaged owing to the small number of shoots in some classes.
Since this study covers a period of three years and includes thous-
ands of shoots, the indexes may be considered as representative. They
result in a very smooth, even graph (Fig. 8). The rate of fruit-bud
formation per node was low when severe pruning was practiced and
increased at a constantly diminishing rate with the decrease in severity
of pruning until the peak was reached at 56 to 65 nodes per vine. At
this point the rate apparently started to decline. Since these curves
are so consistent in direction for each of the three years, it may be
concluded that under conditions similar to those of this experiment
56 to 65 nodes is the optimum number to leave in pruning Concord
grapevines for maximum flower-bud production.

204 BULLETIN No. 393 [July,

SUMMARY

1. The total amount of shoot length produced by a Concord vine
was little affected in these experiments by the severity of the previous
winter's pruning. The vigor of individual shoots was, however, in-
creased proportionately as the severity of pruning increased. The in-
creasing vigor of weak shoots was evidenced mainly by their greater
length and of very vigorous shoots by the growth of laterals. The
average length of the growth per shoot varied inversely with the num-
ber of buds left on the vine at pruning time.

2. The total yield produced by a vine was greatly influenced by
the severity of the previous winter's pruning, the possible number of
fruit clusters being limited by such pruning. Where fewer buds were
left at pruning time and where the number of potential shoots was
reduced, the number of clusters resulting was automatically lessened.
The yield of individual shoots from the buds left to grow was not
noticeably changed.

3. The patterns of shoot growth and of fruit production along
the cane varied similarly from base to tip within the groups having a
similar number of nodes per cane. The degree of severity of winter
pruning treatment given a vine changed proportionately the vigor of
all the shoots on a cane, the more severe pruning increasing the vigor
of the shoots but having little effect on their production.

4. The degree of severity practiced in dormant pruning had a
marked effect upon the formation of inflorescences in the buds along
the shoots growing the following summer. With the more severe
pruning, fewer inflorescences were formed.

5. Except under very unusual conditions during the fruiting
season, the yielding ability of a shoot was largely determined in the
bud the previous year, while its vigor was increased or decreased by
the number of nodes left on the vine at pruning time, the smaller num-
bers resulting in an increase in vigor.

6. In this experiment vines pruned to about 56 to 65 nodes pro-
duced a profitable yield and also produced the largest number of flower
primordia in the buds of the young shoots for the following year's
crop.

PRACTICAL APPLICATION

The grower's problem is to secure high annual yields of marketable
fruit and at the same time to cause the vine to form the largest in-
florescences possible in the buds along the growing shoot for the future
crop. Usually conditions that favor the formation of large flower

1933] GROWTH AND PRODUCTION IN THE CONCORD GRAPE 205

clusters also favor a large number of flower clusters.4* Winter prun-
ing modifies the immediate crop, mainly by limiting the number of
clusters that can be produced. It influences the following year's crop
by affecting the condition of the new shoots and their ability to form
flower buds.

The grower should look upon his vines as individuals and, allow-
ing for gradations in vigor resulting from the presence of insects or
diseases, soil differences, and weather conditions, should handle them
in such a way that vine growth and yield of well-matured clusters are
balanced yearly.

The plants should have sufficient vigor and enough shoots, properly
located, that will ripen into desirable canes, to produce a good crop.
Since the condition of the crop cannot readily be determined while
in the bud, the best available index that can be used at pruning time
during the dormant season is the growth of the last season's shoots.

If most of the shoots were short and were too weak to produce
laterals, the vine was pruned too lightly ; that is, too many nodes were
left the previous season. More severe pruning should be practiced, de-
pending on the degree of weakness found.

If the shoots were so vigorous that they produced more than a
third of their combined terminal and lateral length in laterals, the
previous winter's pruning treatment was too severe and more nodes
should be left in order to obtain higher yields the coming season and
maximum fruit-bud formation for the next crop.

Concord vines grown under conditions similar to those occurring
in the University vineyard and pruned to about 56 to 65 nodes will
bear shoots that are vigorous but not sufficiently vigorous to produce
much, if any, lateral growth. Vines with such a type of growth can
carry large-sized bunches to full maturity and at the same time they
have enough vigor to differentiate large flower clusters in the nodes
along the growing shoots for the following year's crop.

After the severity of pruning treatment for the individual vine
has been determined in terms of number of nodes to be left, the canes
should be selected which will bear the following year's crop. Colby and
Vogele5* found that shoots with a diameter of about ^ inch measured
between the third and fourth nodes and well matured out to the tip
will make the most productive canes the following year. Canes of this
type, with few laterals, should be selected as arms to form the frame-
work of the vine since the buds on these canes carry many and large
inflorescences.

206 BULLETIN No. 393

LITERATURE CITED

1. CHANDLER, W. H., and HEINICKE, A. J. Some effects of fruiting on the

growth of grape vines. Amer. Soc. Hort. Sci. Proc. 22, 74-80. 1925.

2. CLARK, J. H. Some effects of pruning on grape production. Amer. Soc.

Hort. Sci. Proc. 22, 80-84. 1925.

3. COLBY, A. S. Additional notes on pruning and training grapes. Amer. Soc.

Hort. Sci. Proc. 22, 415-420. 1925.

4. — and TUCKER, L. R. Growth and fruit production studies in the

grape. Amer. Soc. Hort. Sci. Proc. 25, 210-216. 1928.

5. — — and VOGELE, A. C. Notes on pruning and training Concord

grapes in Illinois. Amer. Soc. Hort. Sci. Proc. 21, 384-387. 1924.

6. GOFF, E. S. Investigation of flower-buds. Wis. Agr. Exp. Sta. Rpt. 18,

304-316. 1901.

7. KEFFER, C. A. The fruiting habit of the grape. Tenn. Agr. Exp. Sta. Bui. 77.

1906.

8. MANEY, T. J. Grape pruning — the spur and long cane systems compared.

Iowa Agr. Exp. Sta. Bui. 160. 1915.

9. PARTRIDGE, N. L. A note on the fruiting habit of the Concord grape. Amer.

Soc. Hort. Sci. Proc. 18, 193-196. 1921.

10. — The fruiting habits and pruning of the Concord grape. Mich.

Agr. Exp. Sta. Tech. Bui. 69. 1925.

11. SCHRADER, A. L. Growth studies of the Concord grape. Amer. Soc. Hort.

Sci. Proc. 20, 116-122. 1923.

12. The Concord grape — Pruning and chemical studies in relation to

the fruiting habits of the vine. Md. Agr. Exp. Sta. Bui. 286. 61-118.
1926.

13. The effect of fruiting on the shoot growth of the Concord grape.

Amer. Soc. Hort. Sci. Proc. 27, 170-174. 1930.
14. SWARTWOUT, H. G. Fruiting habit of the grape. Amer. Soc. Hort. Sci. Proc.

22, 70-74. 1925.

DEFINITION OF TERMS

Shoot. The young growing branch originating from a bud. All fruits are
borne on shoots, but not all shoots bear fruit.

Terminal or main shoot. The one central or principal shoot starting at the
bud.

Lateral. A secondary growth arising from the main shoot the same year
that the shoot grows.

Cane. A shoot of the previous season which may be left as an arm at prun-
ing time.

Node. The enlarged portion or joint of the shoot at which the tendril, leaf,
bud, and cluster are or may be borne, or the joint of the cane where the bud or
shoot may be attached.

Internode. The part of the cane or shoot between two nodes.

Spur. A short piece of the base of a cane, having one to four nodes with
one or more buds each, where renewal wood may be obtained at pruning time.
Sometimes known as a renewal spur.

Bud. An undeveloped shoot.

Fruit bud or mixed bud. A bud in which a shoot bearing flowers originates ;
a bud containing rudiments of both shoot and flowers.

UNIVERSITY OF ILLINOIS-URBANA