419
Effects of annual crown pruning and serial propagation on rooting of stem cuttings
from Douglas-fir
DoNALD L. CorEs
Pacific Northwest Forest and Range Experimem Station, United States Departmem of Agriculture, Forest Service, Corvallis,
OR, U.S.A. 9733/
Received Octo per 28, J 982' Accepted January 19, 1983 COPES, D. L. 1983. Effects of annual crown pruning and serial propagation on rooting of stem cuttings from Douglas-fir. Can.
J. For. Res. 13: 419-424.
Success of rooting from stem cuttings of 14 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) clones increased signifi­
cantly from 42% in 1974 to 67% in 1981. The increase was slightly more than 3% each year despite ortet age increasing from
I 0 and 13 years in 1974 to 17 and 20 years in 1981. The greatest increase occurred from the 3rd through the 6th year of annual
rooting trials. Yearly pruning of ortets and rooted ramets of the same clones is thought to have reinvigorated shoots from the
pruned crowns of trees. Several annual prunings seemed to be required before average rooting potential increased markedly.
No translocation of the reinvigoration stimulus from the pruned to the adjacent unpruned areas of the same trees was detected.
Rooting of cuttings from ortets from pruned areas was at least 9% more than cuttings from unpruned areas. No additional
invigoration from serial propagation of cuttings was noted for rooting potential, but such cuttings grew a little taller and slightly
less plagiotropic 1 year after rooting than were ramets propagated from pruned ortets. Significant clonal variation was found
with all treatments. Evidence of a change in physiological vigor of the ortcts and rooted ramets was externally visible in the
formation of abundant lammas shoots on pruned areas of the 17- and 20-year-old ortets and rooted ramets. Abundant lammas
growth is normally found only on Douglas-fir trees less than 10 years old.
COPES, D. L. 1983. Effects of annual crown pruning and serial propagation on rooting of stem cuttings from Douglas-fir. C an
J. For. Res. 13:419-424.
.
La reussite d'enracinement des boutures de rameaux de 14 clones de Pseudotsuga menziesii (Mirb. ) Franco augmenta de
fa!fon nette, pussant de 42% en 1974 a 67% en 1981. Cctte augmentation se chiffrait a un peu plus de 3% par annee malgre
!'augmentation de !'age des pieds-meres qui passait de 10 a 13 ans en 1974, puis de 17 a 20 ans en 1981. La plus grande
augmentation dans l'enracinemcnt se produisit a partir de Ia 3c jusqu'a Ia 6" annee des essais annuels. Une taillc annuelle des
pied-meres et des rameaux enracincs d'un memc clone semble avoir revigorc les ramcaux preleves des cimes emondees de ces
arbres. II semble egalcmcnt que plusieurs taillcs annuclles soicnt requiscs pour obtenir un potentiel d'enracinement nettement
augmente. De plus, !'auteur ne decela pas, sur un meme arbre, de transfer! de ce stimulus dans l'enracinement des parties de
cime emondees vcrs cellcs voisines qui ne lc furent pas. La rhizogencse des boutures en provenance des pieds-meres aux parties
de cime tai!lees s'est avcrec 9% superieure a celle des boutures prclevees sur des cimes demeurees sans traitements. De plus,
!'auteur n'obscrva pas de vigueur additionnclle dans l'enracinement, suite a une propagation en serie des boutures, cepcndant
de telles bouturcs pousserent un peu plus ct furent scnsiblement mains plagiotropes, I an apres l'enracinement, compara­
tivcment aux rameaux prelcves des pieds-meres emondes. On note une nette variation clonalc entre tous les traitements, de
meme que !'evidence d'un changement en vigueur physiologique chez ces pieds-meres et les boutures racinees, cette derniere
se traduisant par Ia formation d'abondantes pousses d'aoOt, produites sur ces parties taillees des pieds-mercs ages de 17 et 20
ans ct sur lcs bouturcs racinces. La presence d'abondantes pousscs d'aoOt represente un phenomene normal sur les Pseudotsuga
ages de moins de 10 ans.
[Traduit par le journal]
Introduction
Many reports on various rooting studies with
Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)
are available. The sample of existing literature
presented below merely indicates the scope of past
work. Propagation by stem cutting was started in the
United States in the 1930's (Griffith 1940; McCoulloch
1943), but the rooting techniques were little used until
the intensive interest in tree improvement in the 1960's
resulted in numerous studies on rooting of Douglas-fir
'Revised manuscript received January 18, 1983.
stem cuttings. Investigations were made in the fol­
lowing areas: cultural treatment (Black 1972; Cornu
1973; Ross 1975), paired cutting technique (Brix and
Barker 1973), time of year (Roberts and Fuchigami
1973), bud and cambial activity (Sheila and Roberts
i 975), aging (Roberts and Moeller 1978), shoot origin
(Black 1972), photoperiod ( Bhella and Roberts 1974),
root anatomy (Heaman and Owens 1972), rooting me­
dia (Copes 1977), growth rate and tree form (Copes
1976), and bud dormancy (Roberts eta/. 1974). Root­
ing trials in several of these areas were also made by
Brix and Barker ( 1973), with shoots from adult trees.
Literature on conifers generally indicates that most
CAN.
420
J.
FOR. RES. VOL. 1.1.
llJH.1
conifers root easily when young. but rooting potential
decreases as trees mature (Hyun 1967). No decrease
was noted for Douglas-fir cuttings between ages I and
9 years, but a sharp decline occurred after age 9 (Black
1973). In another study, no decrease in rooting poten­
tial was noted when 14 Douglas-fir clones were tested
each year from year 12 through year 16 (Roberts and
Moeller 1978). The neg<ltive effect of advanced phys­
iological age of the ortet was demonstrated in France,
where 64o/r of the cuttings from I 0-year-old Douglas-fir
trees rooted, but only 18% of the cuttings from
60-year-olcl trees rooted (Cornu 1973). A del'inite de­
crease in rooting potential occurs as Douglas-fir trees
mature, but the literature is not clear about when the
decrease occurs. It does not appear to be correlated with
the onset of flowering (Roberts and Moeller 1978).
Annual pruning or hedging treatments ha vc been suc­
cessfully used in "Radiata pine" to retard the decline in
rootability associated with aging (Libby et a/. 1972).
Cuttings collected from the pruned crowns of adult
Douglas-fir trees rooted better than shoots collected
from unpruned areas of the same trees (Black 1972).
The age of trees at first pruning was not reported be­
cause the trees had not been pruned as part of a formal
study. They had been pruned at unknown dates to keep
branches away from overhead utility lines. Rein­
vigoration likely occurred as a result of the cultural
treatments rather than rejuvenation.
Another method used to maintain high rooting poten­
tial over a period of years is to serially propagate cut­
tings from other rooted cuttings. Serially propagated
adult Douglas-fir clones rooted better (45%) than did
shoots taken from the original ortets (I%) or from grafts
(9%) (Black 1972). How many years Douglas-fir can be
serially propagated and maintain a juvenile or rein­
vigorated condition is unknown, nor whether they can
retain such a condition if annual pruning or hedging is
delayed I to 4 years after rooting.
Although a wealth of information exists on rooting
Douglas-fir, information is lacking in several fields or
published results are conflicting. This study provides
information that will help elucidate the problem areas.
Annual rooting trials from 1974 through 1981 were
evaluated. The major objectives were to provide infor­
mation on the effects of annual crown pruning on rein­
vigoration of cuttings as demonstrated by increased
rooting potential; to determine if rooting potential
decreased between ages I 0 and 20; and to evaluate
invigoration effects of serial propagation on rooting
potential, shoot growth, and growth habit.
10 and 13 years old in 1974 and had been selected for cutting
propagation after. graft tests had identified them as being
highly graft compatible <Copes 1981 ). Ortet cuttings (CO),
consisting entirely of the past season's growth. were gathered
in Januury or February from the lower 2 m of each tree. The
trees were approximately 4 m tall in 1974 and many grew to
greater than 12 m by 1981 . Branch tips and !urge first- and
second-order lutcral brunches were pruned for cuttings. From
1974 through 1980, shoots were clipped only from the lower
2 m of each tree; the area above 2 m was allowed unrestricted
growth until 1981. In 19!! I shoots were gathered !r' om both
the lower 2-m pruned area and the previously unpmned whorl
of branches immediately above the 2-m pruned area. Cuttings
for serial propagation (CC) were gathered from 220 rooted
ramcts of II of the same 14 clones mentioned above. The
ramcts had been rooted in 1972 unci 1973 and planted in the
field in 1975 and 1976. They were not pruned until 1979. At
that time they were about 2 m high. Cuttings were pruned
annually after 1979.
Shoots were stored in plastic bags at 1- zoe for 1-30 days
after field collection. Standard rooting procedure was as fol­
lows: trim the cuttings to 10- to 15-cm lengths. submerge
them in a satmated solution of Captan fungicide for I min, dip
the basal 2-3 em of each cutting in 0.5% indolebutyric acid
(5000 ppm) in 50% ethanol for 5-20 s. and insert the lower
2-4 em of each cutting in the rooting medium. Needles were
not removed from the portion of stem buried in the rooting
medium. No hormone was used before 1975.
Cuttings were reared in two plastic covered houses located
outdoors. Cuttings were rooted in two 1.8- by 16.5- by 0.7-m
raised beds. Temperature at the cutting base was maintained
at 21 ± 3°C with lead heat cables. Watering and humidity
were controlled automatically with Mist-A-Matie1 nozzles. A
fine grade of mason's sand was used us the rooting medium
in 1974 and 1975; a 2: I mix of sphagnum- peat moss and
mason's sand each year after 1975 (Copes 1977).
Weekly application of dilute concentrations of one of four
fungicides (Caplan. Fcrbam, Bcnlate, and Banrot) were used
to control root rot and foliage diseases. A complete, water­
soluble fertilizer (20-20-20) was applied weekly after roots
were first visible on the base of the cuttings. Cuttings re­
mained in the propagation beds until November m· January,
when the rooted cuttings were lifted and transplanted into
outdoor beds for I additional year of growth.
Yearly observations on rooting success were made in
November or January. Analysis of variance tests were used to
evaluate annual rooting potential, to compare percentage
rooting of CC with annual pruned CO from 1979 through
1981, to compare 1980 shoot growth rate and stem angle of
CC and CO cuttings after one season in the transplant beds,
and to evaluate the reinvigoration effects of annual pruning on
rooting potential. All percentage data in Tables I, 2, and 3
were converted to arc sine values before analysis. Growth and
stem angle were measured in September 1980 on CC and CO
cuttings, which had grown one season in the transplant beds.
Methods
2Trade or proprietary names are included for information
purposes only and do not imply any endorsement by the
Canadian Journal of Forest Research and the United States
Department of Agriculture.
Annual rooting trials with 14 coastal Douglas-fir clones
were started in February 1974 and were continued with the
same clones through 1981 at Corvallis, Oregon. Ortcts were
COPES
I . Average annual rooting percentage and, in parentheses, number o f cuttings tested f or the years 1974 through 1981
TABLE
Clone
No.
3
4
14
20
23
25
97
102
106
109
172
197
223
241
X/"i.N
" 1978
TABLE
421
Year of rooting" 1975
1974
5 1(154)
41(308)
57(336)
36(1401)
78(96)
80( 104)
33(235)
66(123)
17(416)
83(245)
40(319)
41(235)
16(248)
23(349)
73(2 10)
18( 186)
60(216)
27( 196)
49(252)
59(188)
32( 155)
58(48)
45(284)
88( 172)
49(255)
61(163)
16(134)
37( 134)
49(486)
37(459)
15(407)
27(541)
58(585)
38(50 1)
49(472)
32(219)
42(4569)
44(2593)
X
1979
1977
1976
1980
61(7,50)
55(720)
65(1005)
67(630)
58(360)
76(693)
37(515)
62(1080)
68(600)
76(2500)
64(630)
7 1( 1190)
59(690)
66(660)
64(450)
58(255)
65(562)
62(539)
52(360)
65(205)
32(559)
56(660)
77(554)
72(720)
38(419)
23(440)
74(660)
74(406)
66(406)
25(406)
66(406)
49(406)
62(406)
41(406)
66(406)
42(406)
74(406)
67(406)
36(406)
31(406)
62(406)
49(6463)
54(5684)
66( 12023)
"i.N 1981
71(1035)
68(570)
68(360)
46(300)
65(360)
73(876)
70(954)
56(864)
63(612)
62(856)
81(864)
36(571)
77(864)
65(864)
82(864)
67(876)
74(852)
34(864)
82(864)
64(3332)
55(3288)
52(3796)
55(4325)
57(2915)
67(2961)
38(2913)
63(3400)
52(2570)
77(5776)
64(3776)
61(3625)
37(3082)
66(3433)
60(6215)
67(11645)
59(49192)
data nre not pre cnted bccnuse of excessive loss f'rom disease.
2. Percentage rooting potentials of II clones for cuttings from ortets (CO) and cuttings from rooted cuttings (CC)
(number of cuttings in parentheses)
Year of rooting
Clone No.
3
14
20
23
97
102
106
109
172
197
241
gj"i.N
X/"i.N
co
72( 173)
74(221)
50(165)
57(180)
22(77)
59(19 1)
8 1(229)
82(303)
59(153)
74(200)
74(193)
X
cc
49(68)
54(293)
83(168)
60(156)
55(62)
63(385)
29(80)
8 1(256)
69( 183)
59(479)
58(170)
62(2300)
68(2085)
65(4385)
co
58(600)
64(407)
62(359)
55(420)
35(4 19)
42(360)
39(360)
77(760)
70(480)
68(360)
56(555)
"i.N
198 1
1980
1979
cc
co
60(289)
62(360)
50(330)
41(740)
25(140)
45(849)
14(687)
64(987)
55(239)
71(420)
56(622)
59(5080)
49(5663)
54(10743)
Each clone was treated as a replicate of the performance of the
various treatments. Split plot analysis of variance tests with
years as the split plot effect was used on the data in Table 2.
In this case clones were used as replication. Rooting data for
1978 were not presented because excessive loss from disease
prohibited accurate assessment of rooting. The average loss
for the other years was small and fairly constant bewcen
years.
Results
Rooting potential of annually pruned ortets did not
decrease when tree age increased from I 0 and 13 years
in 1974 to 17 and 20 years in 1981. Instead, rooting
86(420)
67(420)
67(168)
73(420)
31(420)
73(420)
63(420)
83(420)
72(420)
83(420)
86(420)
cc
59(420)
46(420)
66(420)
5 1(420)
48(168)
81(420)
66(420)
81(420)
62(420)
84(420)
79(420)
67(4368)
71(4368)
69(8736)
co cc
70(1 193)
67(1048)
61(692)
63( 1020)
32(916)
59(97 1)
59(1009)
80(1483)
69(1053)
76(980)
69(1168)
58(777)
53( 1073)
63(918)
46(1316)
40(370)
62( 1654)
33(1187)
7 1(1663)
62(842)
70( 1319)
64(1212)
65(1 1533)
58(1233 1)
potential increased from 42 to 67% (Table I). Current­
year rooting exceeded that of the preceding year in five
of six comparisons. The increase averaged about 3%
each year, although the greatest increase occurred be­
tween 1974 and 1977 (Table I). Annual rooting data for
all 14 clones are presented in Table I. Clones and years
(linear effect) were both significant at P s:; 0.000 I.
Comparisons within and between clones are more accu­
rate for 1979 through 1981 because of greater within­
clone replication. Mean repeatability (r2) for years
1979 to 1981 was 56%, but only 25% for 1974 through
1977.
CAN.
422
J.
FOR. RES. VOL. 13. 1983
TABLE 3. Comparison of rooting percentages for cuttings
TABLE 4. Second-year total height and growth habit (number
from pruned and unpruned crown areas of I 0 ortets taken in
198 1 (number of cuttings in parentheses)
of degrees the leader deviated from the vertical) for cuttings
established from annually pruned ortcts (CO) and from other
previously unpruncd rooted cuttings (CC)
Type of crown area sampled
Ortet No.
Pruned
Unpruned
4
14
97
102
106
109
172
197
223
24 1
48(430)
67(430)
31(430)
73(430)
63(430)
83(430)
72(430)
83(430)
27(430)
86(430)
22(90)
60(90)
31(90)
8 I (90)
42(45)
88(135)
52(90)
61(90)
2 1(90)
62(45)
X/'kN
63(4300)
54(855)
In 1979, 1980, and 1981, CC were compared with
CO for II of the same 14 clones. Average annual
rooting in all 3 years by CO was greater than by CC of
the same year (Table 2). Pruning of rooted ramets for
serial propagation was not started until 1979, but ortets
were pruned annually after I 974. The difference in
rooting potential between CO and CC was significant
(P :s 0.05). Significance for clones was P ::; 0.000 0 I ;
for linear effects, P :s 0.05; and for quadratic year
effects, P :5 0.0001. Interactions between type of cut­
ting and years were not significant.
In 1981 the effect of annual pruning on rein­
vigoration or maintenance of juvenility was evaluated
by comparing rooting behavior of shoots collected from
both pruned and unpruned crown areas of the same 10
ortets. Shoots for the unpruned treatment were gathered
from branches immediately above the lower 2-m pruned
area from which cuttings had been taken each year since
1974. Cuttings from the unpruned areas were larger
than those from the pruned areas and apparently more
vigorous, but 63% of the shoots from pruned areas
rooted whereas only 54% of the shoots from the un­
pruned areas of the same trees rooted (Table 3). The
effect of pruning was significant (P :s 0.05). No
growth tests after rooting were made on cuttings after
rooting. Rooting percentage by cuttings from unpruned
areas was greater in only 2 of the 10 ortets. The two
clones, 102 and 109, had been among the best rooting
clones in 1974 when cuttings were collected from pre­
viously unpruned ortets (Table I). They were not influ­
enced by time or pruning and still rooted readily 7 years
later. If data from the two good rooting, nonresponding
clones are deleted from the comparison, cuttings from
the pruned areas rooted 60 vs. 43% from unpruned
areas. This 17% difference more accurately illustrates
the increase that can be expected from a majority of the
Height (em)"
Growth habit
n''
Clone
No.
co
cc
co
cc
3
4
14
20
23
25
97
102
106
109
172
197
223
24 1
39
16
23
22
20
30
28
!9
25
33
32
16
18
25
40
21
27
47
32
46
32
18
32
32
26
36
19
23
44
56
50
47
57
60
50
55
65
45
41
47
46
45
46
57
57
50
49
43
62
52
59
72
60
54
X/'kN
25(350)
29(350)
54( 140)
51(140)
1'Each value is average of·measuremcnts from 25 trees. 1'Euch value is average or measurements from I 0 trees. clones after they have been pruned for several years.
Height and stem angle were measured in 1980 on
ramets of all 14 clones after I year in the transplant
beds. The CC ramets averaged only 4 em taller than the
CO ramets (Table 4). This difference was significant
statistically (P :5 0.00 I ). Differences between clones
and the clone by type of cutting interaction were also
significant (P :s 0.001). Difference in annual shoot
growth between CC and CO ramets cannot be attributed
to the lengths of cutting placed in the rooting beds the
previous year because both types had been trimmed the
same. Shoots from ramets, however, had larger stem
diameters than those from ortets at the time of place­
ment in rooting beds. The CO shoots were only 75% as
heavy as those from CC (2.62 vs. 3.54 g/cutting).
Measurements of plagiotropism after I year of
growth in the transplant beds indicated that cuttings of
I I of 13 clones were slightly more orthotropic for CC
than for CO. Serially propagated ramets averaged 51
degrees from the vertical, whereas CO ramets averaged
54 degrees (Table 4). The difference between CC and
CO was significant (P :s 0.01). The two-way inter­
action between clones and type of cuttings was also
significant:(? :5 0.001).
Additional evidence of reinvigoration or mainte­
nance of juvenility by annual pruning was seen in 1981
branch morphology observations on ortets, rooted ram­
ets, and grafts. Presence of Jammas growth (2nd tlush
branch growth) normally occurs in trees less than I 0
years old, although heavy rainfall in June and July or
·
COPES
heavy application of fertilizer can at times induce older
trees to develop lammas shoots (personal observations).
Abundant lammas growth in mature trees is unusual. In
I981 , lammas growth was found on pruned areas of
seven of eleven 17-year-old ortets, whereas none were
found on unpruned areas of the 7 trees, or on either
pruned or unpruned areas of the other four ortets. Ob­
servations on the rooted ramets used for serial propaga­
tion revealed lammas growth on 2\5 of 220 ramets. All
215 ramets that formed lammas shoots had been pre­
viously pruned, but the 5 ramets that had not formed
lammas shoots had never been pruned. Examination of
crowns of 6-year-old, unpruned grafts of the same
clones revealed no lammas growth.
Discussion
Juvenile and adolescent Douglas-fir trees can be
propagated for rootstock in seed orchards and for com­
mercial Christmas trees. The high rooting potential ex­
hibited by most juvenile and adolescent clones makes
this possible. About 67% of over II 000 cuttings were
rooted in I 981 when they were 17 and 20 years old. lt
is significant that no decrease in rooting potential oc­
curred when tree age increased from I 0 to 20 years. The
expected response would have been a decrease. The
absence of decreased rooting potential is probably the
result of invigoration from annual pruning. Roberts and
Moeller ( I 978) found similar results with I 2- to
16-year-old trees.
The actual amount of invigoration from annual
pruning of ortets is hidden in the 25% increase in root­
ing potential. A portion of the 25% increase resulted
from better control of disease and rooting environment
during succeeding years of the study. The amount of
int1uence from these environmental factors is estimated
as the I 2% difference between rooting of shoots from
unpruned trees in 1974 and unpruned areas of the same
trees in I 98 I (42 vs. 54%). The remaining portion
(l3%) is attributed to the invigorating intluence of
annual crown pruning.
The maintenance of high rooting potential during
Douglas-fir adolescent years supports Roberts and
Moeller's ( I 978) findings, that rooting potential of 12­
to 16-year-old Douglas-fir trees did not decrease but
simply varied annually from 63 to 75%. The 12- to
16-year-old trees had been pruned annually for rooting
trials. Quite different results were reported by Black
(1972), who worked with unpruned 14- to 20-year-old
trees. He found that rooting averaged less than 5%.
Much of the difference between Black's results and
those of this study and Roberts and Moeller's may have
resulted because Black's cuttings came from crown
areas that had never been pruned.
No increase in rooting potential occurred in unpruned
areas. Rooting of cuttings from branches immediately
423
above the pruned zone was significantly less than of
cuttings gathered from pruned areas of the same trees.
The lack of transfer of reinvigoration factors to
unpruned areas, as evidenced by increased rooting po­
tential, supports Black's (1972) findings on partially
sheared trees under utility lines.
No invigoration effects from serial propagation were
detected other than slightly greater shoot and less severe
plagiotropism. Cuttings from rooted ramets actually ex­
hibited less rooting potential than CO. One possible
reason for the difference was that pruning of ramets was
avoided during the 3 or 4 years immediately after
rooting. Time for unrestricted growth was needed for
the crown of each ramet to enlarge. Ortets were pruned
annually during that 3 to 4 years, and consequently, CO
continued to increase in rooting potential. The lack of
a positive rooting response to serial propagation is con­
tradictory to Roberts and Moeller's (1978) results. They
serially propagated six mature Douglas-fir trees and
detected positive effects of reinvigoration as evidenced
by increased rooting potential. They may have obtained
positive results, while I found none because the ortets
in my study had been pruned annually. The standard
against which they evaluated their serially propagated
cuttings was the rooting of cuttings taken from pre­
viously unpruned ortets. A 3-year unrestricted growth
period following initial rooting preceded the collection
of shoots for serial propagation in both studies.
Pruning was usually effective in stopping or slowing
maturation. Only the rooting of cuttings from ortet 223
shows a continuous downward trend and, even that
clone's serially propagated cuttings, in I981 showed
positive signs of increased rooting potential over that of
the previous 2 years. Future study will be required to
determine if additional time is needed for serial propa­
gation to show a positive effect on average annual
rooting.
Pruning also promoted or maintained the juvenile
growth and vigor that result in the formation of abun­
dant lammas shoots. The relation of juvenility or youth­
ful vigor to presence of lammas growth in Douglas-fir
is well known, but the correlation between lammas
shoot growth and rooting of stem cuttings in 17- to
20-year-old trees is not clear. ln 1981, several of the
ortets with the greatest rooting potential did not form
lammas shoots, but several of the poorer rooting ortets
did. Thus, the presence of lammas shoots normally
denotes juvenile growth or vigor, but lammas does not
indicate that such trees have a higher rooting potential
than similar trees that do not form lammas shoots.
Growth rate and habit of cuttings after rooting is of
practical importance because it directly affects how the
cuttings can be used. Rooted cuttings that grow slowly
or are prone to severe plagiotropism are less desirable
than are faster growing, upright trees. This is true for
424
CAN.
J.
FOR. RES. VOL. 13. 19H3
the production of rooted cuttings for the Christmas tree
industry or for compatible rootstocks. Growth in the
transplant beds the year after rooting showed good
growth for both types of cuttings. The CC were only
slightly taller and more upright in growth habit than
were CO.
The time required for plagiotropic Douglas-fir ramets
to become orthotropic is correlated with tree age. Cut­
tings propagated from 3-year-old seedlings all became
orthotropic the year after rooting (Franclet 1974),
whereas cuttings from 4- to 8-year-old ortets required
about 7 years before most ramets became orthotropic
(Copes 1976). Field tests will be necessary to determine
the number of years required for ramets of 17- to
20-year-old trees to become upright. The required time
might be less for CC than for CO because annual
pruning appears to have slightly increased the vigor of
CC ramets.
BHELLA, H. S., and A. N. ROBERTS. 1974. The influence of
photoperiod and rooting temperature on rooting of
Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco). J.
Am. Soc. Hortic. Sci. 99(6): 551-555.
--- 1975. Bud and cambial activity in Douglas-fir as
related to stem cutting rootability. For. Sci. 21(3):
269-275.
BLACK, D. K. 1972. The influence of shoot origin on the
rooting of Douglas-fir stem cuttings. Comb. Proc. Int.
Plant Prop. Soc. 22: 142-157.
--- 1973. Influences of shoot origin and certain post
scverence treatments on the rooting and growth character­
istics of Douglas-fir (PseudOisuga menziesii (Mirb.)
Franco) stem cuttings. Ph.D. thesis. Oregon State Univer­
sity.
BRIX, H., and H. BARKER. 1971. Rooting of Douglas-fir
cuttings by a paired-cutting technique. Proc. Int. Plant
Prop. Soc. 17: 118- 120.
--- 1973. Rooting studies of Douglas-fir cuttings. Can.
For. Serv., Pac. For. Res. Cent. Inf. Rep. BC-X-87.
COPES, D. L. 1976. Comparative leader growth of Douglas­
fir graft, cuttings, and seedlings. U.S. For. Serv. Tree
Plant. Notes. 27(3): 13- 16.
1977. Influence of rooting media on root structure and
rooting percentage of Douglas-fir cuttings. Silvuc Genet.
26(203): 102-106.
1981. Selection and propagation of highly graft­
compatible Douglas-fir rootstocks-a case history. U.S.
Dep. Agric. For. Serv .. Res. Note PNW-376.
CORNU, D. 1973. Essais prcliminaircs sur Ia selection de
clones bouturablcs de Douglas ( Pseudot,\'llg(/ men::iesii
Franco). Ann. Sci. For. 30(2): 157-173.
FRANCLET, A. 1974. Bouturage du Douglas--enracincment
de bouturcs de flechcs prclevccs sur des semis de 3 ans
(3 + 0). Rapport Annucl de !'Association Foret­
Cellulosc. pp. 29-43.
GRIFFITH, B. G. 1940. Effect of indolebutyric acid, in­
doleacetic acid and alpha napthalcncacctic acid on rooting
of cuttings of Douglas-fir and Sitka spruce. J. For. 38:
496-501.
HEAMAN, J. C., and J. N. OWENS. 1972. Callus formation
and root initiation in stem cuttings of Douglas-fir (Pseudo­
tsuga menziesii (Mirb.) Franco). Can. J. For. Res. 2:
12 1- 134.
HYUN, S. K. 1967. Physiological differences among trees
with respect to rooting. 14th International Union of Forest­
ry Research Organizations Kongress, Miinchcn. Sect. 22.
pp. 168-190.
LIBBY, W. J A. G. BROWN. and J. M. FIELDING. 1972.
Effects of hedging radiata pine on production, rooting. and
early growth of cuttings. N.Z. J. For. Sci. 2: 263-283.
McCOULLOCH, W. F. 1943. Field survival of vegetatively
propagated Douglas-fir. J. For. 41: 211-212.
ROBERTS, A. N., and L. H. FUCI-IIGAMI. 1973. Seasonal
changes in auxcn effect on rooting of Douglas-t1r stem
cuttings as related to bud activity. Physiol. Plnnt. 28(2):
2 15-221.
ROBERTS, A. N., and F. W. MOELLER. 1978. Speculations
relating to the loss of rooting potential with aging of
Douglns-fir stock plants. Plant Prop. 24( I): 2-4.
ROBERTS. A. N., B. J. TOMASOVIC, and L. H. FUCHIGAMI.
1974. Intensity of bud dormancy in Douglns-fir and its
relation to scale removal and rooting ability. Physiol. Plant.
31:21 1-216.
Ross, S. D. 1975. Production. propagation, and shoot elon­
gation of cuttings from sheared !-year-old Douglas-fir
seedlings. For. Sci. 21(3): 298-300.
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