FOREST RESEARCH NOTES
US.DEPARTMENT OF AGRICULTURE
FOREST SERVICE
CALIFORNIA FOREST AND RANGE
EXPERIMENT STATION*
STEPHEN N. WYCKOFF,
No.
Director
85
March 3,
1953
PINE POLLEN COLLECTION DATES - ANNUAL
AND GEOGRAPHIC VARIATION3^
By J.
W.
Duffield
Activity in pine breeding has increased throughout the temperate
forest regions of the world since the Institute of Forest Genetics issued
its first summary of pollen collection dates in 1947•
Cooperation between
The information most essen
tial for conducting cooperative breeding operations are the dates of pollen
pine breeders has increased at the same time.
collection (which also approximate the dates at which the bagging of flower
buds to control pollination should be done) for various species at various
localities.
This publication,
adding four years'
data to the note issued
in 1947, covers a period of 14 years.
In addition, some data are presented
on the relation between temperature and development of catkins and on the
effect of altitude
on time of pollen collection.
still fragmentary,
should assist workers elsewhere to generalize from the
data collected at the
These new data,
although
Institute of Forest Genetics.
Some notes on the pollen collection techniques used at the
Institute
of Forest Genetics^/ should help in the interpretation of the data which
follow.
Catkins,
or twig-tips bearing catkins,
catkins on a tree are starting to open.
corresponds rather closely to the date
are picked when the
first
Thus a collection date usually
on which pollen shedding starts.
The collection date also corresponds to a date five days to a week later
than that on which bagging of conelet buds on the same tree would be advis
able.
Complete extraction of the pollen requires from one to five days or
rarely longer.
If the pollen has been extracted under conditions of low
1/ A revision of Duffield,
collection by the
Exp.
Institute
Sta. Research Note No.
J. W.
1947.
Dates and places of pollen
of Forest Genetics.
54.
Calif.
2/ Cumming, W. C, and F. I. JUghter;.-
194#.
Methods used to control
pollination of pines in the Sierra Nevada of California.
Cir. No. 792,;
Forest and Range
5 p.
U.
S.
Dept. Agr.
18 p.
* MAINTAINED AT BERKELEY, CALIFORNIA, IN COOPERATION WITH THE UNIVERSITY OF CALIFORNIA.
Agriculture—Berkeley
humidity (from 15 to 30 percent relative humidity) it should be a highly
"fluid" dusrb.
Otherwise it is advisable to reduce its moisture content by
holding it in a desiccator over anhydrous calcium chloride for one to two
days.
If this is not done, the mold spores germinate (these spores cannot
be eliminated'from pollen samples by present methods).
Then the pollen
sample becomes felted into a lumpy mass by the growth of mold mycelia.
Such pollen is of little or no value for controlled pollinations.
Combining the time required for extraction and desiccation,
it is
usually possible to ship pine pollen from one to seven days after it is
collected.
The extraction techniques used at the
Institute of Forest
Genetics^/ result in pollen samples of high purity (with the exception
of mold spores) in spite of the fact that the pollen parents are almost
invariably surrounded by many other pines of the same or different species,
many of which are shedding pollen freely at the time when catkins are col
lected.
Pressure of work during the pollination season seldom permits tests
of pollen germinability immediately following pollen extraction.
Much
reliance is placed on the physical properties of the pollen.
If it is dry
enough to act like a fluid, and no more than one year old, pollen is
usually highly germinable.
Most pine pollen shows high germinability for
many months following extraction if: (I) extraction humidity has been low
enough to prevent molding of the pollen; (2) pollen has been stored at 25
percent to 50 percent relative humidity at a temperature below 5°C
Table 1 has been compiled from the past 14 years'
of the Institute of Forest Genetics.
So far,
phenological records have not been kept.
2
breeding records
systematic and comprehensive
For this reason,
data for many
of the pines and other trees growing in the Eddy Arboretum^/ at Placerville
are lacking.
The trees in the Eddy Arboretum are derived from trees growing in
many parts of the Northern Hemisphere.
tainty,
When known with any degree of cer
the original sites of trees from which pollen producers were derived
are given in Table 1.
Pollen of some species is collected from "wild" trees
growing at the original site.
Pollen of other species is collected from
trees growing in the Eddy Arboretum near Placerville,
Fresh Pond,
at Berkeley,
and at
California.
y Duffield, J. W., and A. G. Snow, Jr.
1941.
Pollen longevity of
Finus strobus and Pinus resinosa as controlled by humidity and temperature.
Amer. Jour. Bot. 28: 175-177.
lj Weidman, R. H.
1947.
Trees in the Eddy Arboretum.
and Range Exp. Sta. Research Note No.
53.
-2-
8 p.
Calif. Forest
The table column showing the number of years in which pollen was
collected is a rough index of reliability.
Figure 1 summarizes the dates of pollen collection for the fourteen
pine species and hybrids from which pollen has been collected for five or
more years in the Eddy Arboretum.
The horizontal lines extend from the
earliest to the latest collection date for each species, and the vertical
bars near the center of each line indicate the mean collection dates.
At
the earliest and latest end of each line is indicated the year in which
the record for earliness or lateness for the species was made.
It will
be noted that, generally, 1947 was a year of early pollen shedding, while
194S was a year of late shedding.
However, the data for P. radiata are
exceptional; 1948, with high January and February temperatures but low
temperatures from March through June,
P.
produced the earliest record for
radiata pollen shedding.
Figure 2 is an attempt to relate pollen shedding dates to temperature.
Three years were selected for study: 1947,
a year of late shedding,
and 1949.
a year of early shedding; 1948,
Pollen collection dates were recorded
for 5 representative species and hybrids for each of these 3 years.
From
thermograph records,
mean
corrected by semi-weekly thermometric readings,
daily temperatures were computed.
These are plotted for the period March
1 through June 21 for each of the 3 years.
of mean daily temperatures,
To establish a
"normal" curve
the following procedure was followed^.
Mean
daily temperatures for the periods 1929-1937, inclusive^/, and 1947-49,
inclusive, were averaged for the period March 1 through June 21.
These
averages were then smoothed by means of computing 7-day moving averages.
Finally,
a free-hand curve was fitted to these averages.
The resulting
curve, of doubtful climatological value, has the advantage of furnishing
a suggestive standard for comparing the course of temperatures in different
years.
This
"normal" curve
each of the 3 years.
is plotted with the mean daily temperature for
It is obvious that, for the period studied,
1948,
the
year of late pollen shedding, was abnormally cold, whereas 1947 was dis
tinctly warmer.
The spring of 1947 started cool and approached normal as
the season progressed.
Pollen shedding dates are quite consistent with
these curves, with the exception of the early shedding of X P.
pollen in 1948.
attenuradiata
This is no doubt a result of the relatively high January -
February tempera tures in 1948.
The late shedding of pollen by this hybrid
in 1949 appears to be the consequence of low temperatures in February.
One further generalization can be made from the data on hand.
Pinus
ponderosa, on the west slope of the Sierra Nevada, grows from 125 to 7,000
feet above sea level.
Pollen collection dates for trees from 1,000 to 6,000
feet elevation have been recorded.
From these data a mean interval of 8
days per 1,000 feet difference in elevation has been computed.
This figure
agrees moderately well with Hopkins1^/ constant of 4 days for each 400 feet
difference
in elevation.
5/ Mirov, N. T.
of Forest Genetics,
manuscript,
Calif.
1939.
Climatological observations at the Institute
Placerville,
California,
Forest and Range Exp.
6/ Hopkins, A. D.
1918.
from 1929 to 1937.
Sta.
The bioclimatic law.
Weather Bureau; Monthly Weather Review - Supplement No.
-3-
Unpublished
U. S. Dept. Agr.
9.
pp.
1-42.
I
Species
37
Balfouriana Balf.
contorta var. bolanderi Parl,
do.
contorta
caribaea Morelet
39
41
39
_
28
:.28
do.
32
Smith
canariensis C.
44
Bungeana Zucc.
do.
Banksiana Lamb.
124W
124W
124W
—
16V
16V
119E
89W
—
117V
109W
—
109W
btachyptgra Shaw
32
—
—
121W
121W
122W
121W
—
-
—
-
—
-
-
-
—
10,000
—
-
—
—
-
—
3,000
2,000
—
-
109W
—
-
]0,000
8,900
109W
] .1 TV
120W
32
—
—
39
38
39
39
—
37
32
32
39
(feet)
0
E
0
E
B
E
E
0
E
0
E
0
E
E
F
E
0
0
E
0
E
0
0
at
: Growing
.
Altitude:
Original site
(N) Long.
do.
ayachuite var.
attenuata X attenuradiata
Stockwell & Righter
x attenuradiata
do.
do.
do.
attenuata Lemm.
Armandi Franch.
do.
arizonica Engelm.
aristata Engelm.
apacheca (see P. latifolia)
...
:Lat.
•
.
e
-
25
12
20
25
15
-
-
-
-
Mar.
-
Apr.
-
Mar.
15
24
20
July 12
May
—
Mar.
—
—
—
Mar.
Apr.
-
Apr.
June 3C
-
1
15
27
25
13
-
-
-
-
Apr.
10
9
2;^
14
11
June 9
May
June 9
May
3
Mar. 31
Mar. 31
May
-
May
Apr.
July 20
-
-
24
27
21
May 22
21
20
Apr.
Apr.
19
Apr.
Mar.
29
22
11
10
8
Apr.
May
May
Apr.
Mar.
July 18
July 23
Mean
May
Apr.
July 27
June
-
-
Apr.
-
—
-
Apr.
May
-
May
July 26
-
Latest
Pollen collection dates
:Earliest
:
•
F, at Fresh Pond, California, Lat. 39 N, Long. 121°W, Alt. 3700 feet.
albicaulis Engelm.
Pinus:
indicates pollen-producing trees growing at original site;
E, at Eddy Arboretum, Placerville, California, Lat. 39°N, Long. 121°W, Alt. 2700 feet;
B, at Berkeley, California, Lat. 38°KL Long. 122°W, Alt. 200 feet; and
0,
Institute of Forest Genetics
Table 1.—Dates, of pine pollen collection by the
l
1
l
1
3
1
2
1
10
3
2
1
1
7
1
1
1
4
8
1
5
3
1
:years
:No. of
•
1
^
1,000
119W
Tames
'see ?o Griffithi)
& Henry
-
-
-•
doo
do.
do.
Lamb.ertiana Douglc
-
39
39
34
-
120W
120W
116W
-
E
0
0
0
May
21
July 1
—
-
F
5,000
5,000
6,000
-
-
Jeffreyi x ponderosa
-
0
—
-
117W
-
33
dOc
21
May
4,000
121W
37
doc
0
22
4
—
June
June
0
5,000
Jeffreyi x Coulteri
34
116W
0
5,000
121W
40
21
24
15
8
14
31
3
June 12
0
7,000
doo
do.
120W
0
6,000
120W
dOo
-
0
5,000
39
39
39
May
0
4,000
-
-
121W
120W
E
Apr.
Apr
-
-
May
0
—
E
E
E
0
E
Mar.
5,000
116W
-
-
-
-
-
81E
9,000
E
Apr
Apr.
Apr.
26
5
19
3
7
5
18
23
26
15
7
7
6
6
May
31
July 9
-
-
-
-
tYune 9
June
—
July 1
June
—
June
-
-
Apr.,
June
-
-
June
May
Apr.
-
Apr.
May
-
May
May
-
25
21
11
14
May
May
11
July 8
.May
—
E
do.
34
-
-
27
-
118W
—
5
19
9
—
Apr.
Apr,
Apr.
Apr
-
37
& Balf•
brutia
-
37
-
June
Apr,
Latest
of
24
19
9
1
21
1
May
27
1
4
3
1
1
1
28
June 8
July 8
July 6
May
June 7
2
3
1
5
June 11
June
3
5
1
2
1
8
2
8
1
1
5
5
2
25
June
5
3
21
17
15
.Tune 18
June
—
June
Apr.
-
May
Apr.
July 16
May
Apr.
May
Apr
11
1
5
15
June
May
1
2
6
4
2
4
3
years
8
24
26
1
22
"
°'Mo
June
-
Apr
Apr.
May
June
Mean
Pollen collection dates
Earliest
E
E
E
0
0
E
doo
Jeffreyi Grevc
Elwc
halepensis varo
halepensis Mill,,
Griffithi MrTLell.
glabra Walt,
dOc
flexilis
excelsa
echinata x taeda
-
echinata x caribaea
—
—
-
93W
-
—
echinata Millc
2,000
4,000
93W
122W
34
121W
5,000
116W
33
37
-
E
E
-
115W
—
E
7,000
-
0
E
6,000
■feet)
at
Growing
120W
38
33
31
do,
;
Altitude:
120W
Lone.
117W
-
39
39
49
51
iN":
Original site
do.
Don
latifolia x
latifolia
slat.
do.
do.
Coulteri D.
Banksiana
contorta var,
doo
dOc
do.
Engelnu
contorta vart
Species
;
Don
7,000
—
E
39
39
39
39
39
39
39
do.
do.
do.
do.
do.
48
47
43
46
42
do.
do.
42
42
do.
do.
do.
do.
do.
do.
do.
do.
37
37
do.
0
6,000
120W
113V
121V
114V
122V
124V
-
2,000
4,000
-
-
-
E
E
E
E
E
E
E
0
5,000
120W
121V
123W
0
4,000
3,000
0
0
0
E
E
2,000
1,000
2,000
0
0
121V
121V
121V
121V
123V
122W
122W
0
ponderosa Laws.
112V
E
pinea L.
35
1
25
15
21
30
-
-
-
-
-
•
June 14
June 3
Apr.
Apr.
Apr.
-
—
-
-
—
Apr.
-
5
May
E
29
Apr.
E
E
Apr.
7
E
-
Apr.
-
-
20
0
E
E
0
E
Mar.
4E
—
-
3,000
—
21
June 8
May
8
Apr.
—
25
E
44
124W
120W
121V
116V
114V
* ;'-
Apr.
-
-
-
-
-
-
June
June
May
May
May
-
-
-
—
-
May
Apr.
Apr.
-
May
May
-
Apr.
-
-
June
Aug.
May
-
-
27
11
28
30
14
20
25
25
12
10
20
2
5
5
June i
-
Latest
14
Apr.
4
11
May
May
Mav
May
May
3
4
5
2
5
27
1
1
1
1
1
1
1
May
2
26
May
2
2
7
4
1
1
1
1
1
2
5
3
1
3
3
1
2
1
1
2
June 20
May
21
June 6
May
May
2
8
6
16
May
May
May
May
27
May
—
11
14
9
30
19
29
Apr.
May
May
Apr.
Apr.
-
May
July 2
-
7
4
July 11
26
1
1
1
6
1
Apr.
19
20
24
16
of
:years
.jNo.
June 2
Apr.
May
May
May
Mean
Pollen collection dates
Earliest
nigra var. austfiaca
Asch. & Graeb.
nigra var. ealabrica Schneid.
nigra vac. cebennensis Rehder
patula Schl. & Cham,
pinaster Ait.
muricata var. borealis P ::2'^Z
Duffield
muricata D.
46
34
47
do.
do.
48
do.
120W
0
39
E
E
monticola Dougl.
118W
E
37
E
0
E
109W
HOW
Altitude
(feet)
32
(N) Long.
Original site
32
:Lat.
Montezumae Lamb,
monophyllg. Torr.
massoniana Lamb,
longifolia (see P. roxburghii
leiophylla Schl. & Cham,
do.
latifolia Sarg.
Species
107W
99W
43
do.
do.
H.
yimnanensis
Chapman
-
Stockwell
washoensis Mason &
do.
virginiana Mill.
do.
Torreyana Parry
39
-
-
33
33
120W
-
8,000
-
-
0
E
F
B
-
E
0
0
117W
E
E
E
E
E
E
E
E
E
E
117W
-
-
-
taiwanensis Hayata
-
-
taeda x caribaea
■
-
taeda L.
-
-
-
-
-
-
-
-
72W
-
-
F
3,000
121W
E
E
0
-
Thunbergii Parl.
E
E
3,000
-
-
-
121W
-
-
-
-
-
44
-
-
-
39
39
-
-
-
-
F
0
122W
-
tabulaeformis Carr.
sylvestris L.
strobus L.
H.
x Sondereggeri
Franch.
Sinensis var.
Sinensis Lamb.
do.
Sabiniana Dougl.
Roxburghii Sarg.
rigida Mill.
rigida x taeda
resinosa Ait.
do.
E
E
E
0
-
-
E
E
-
0
-
-
17
19
June 13
Apr.
11
20
-
25
Feb.
8
Feb.
Apr.
-
-
Mar.
23
18
Apr.
-
2
22
24
May
Mar.
-
-
-
Mar.
Apr. 8
Mar. 26
Mar. 6
Apr.
Apr.
Jan. 28
23
30
4
5
10
23
July 12
Apr.
-
Mar.
May
Apr.
-
-
May
-
May
5
June 8
Apr.
-
-
28
Apr.
17
30
Apr.
Mar.
29
10
24
12
14
25
28
Apr.
May
Apr.
Apr.
-
May
Apr.
25
16
Apr.
Mar.
Apr.
-
-
Apr. 16
-
0
-
-
-
E
Latest
18
12
29
24
25
13
•
1
19
July 2
Apr.
5
8
May
20
Mar.
Mar.
20
25
3
12
14
Apr.
Apr.
Apr.
Apr.
Apr.
1
20
May
May
29
Mar.
4
3
1
3
4
3
1
1
9
1
5
5
2
1
1
24
l
4
2
4
3
6
2
7
1
4
5
2
1
1
Apr. 28
Apr.
of
:years
:No.
20
Apr.
18
8
Apr.
Apr.
17
Apr.
Apr. 26
-
Mar.
June 9
Apr.
Apr.
-
May
May
Apr.
Mean
Pollen collection dates
:Earliest
:
•
-
at
Growing
-
(feet)
Altitude:
:
•
122W
117W
33
34
34
quadrifolia Sudw.
radiata D. Don
78W
40
pungens Lamb.
do.
107W
105W
do.
Engelm.
40
40
42
(N) Long.
113W
scopulorum
:Lat.
Original site
37
ponderosa var.
Species
•
•
'48
47
'47
'48
'47
'48
'47
'38
'39
'48
—i
'47
'48
^
J48
39
I—
'48
47
h-
'47
38
-H
38,49
—i
'46
JAN
31
49
FEB
28
MAR
Figure
31
APR
X
silvestris
resinosa
murraybanksiana
banksiana
—I
47
ponderosa
ponderosa var. arizonica
X
—I
'48
I—
armandi
—i
I—
taeda
attenuradiata
radiata
30
MAY
31
1#- Pollen collection dates
for species collected for five or
more years
latifolia
coulteri
'48
'47
'4.7
griffithi
'48
47
I—
P. strobus
in the Eddy Arboretiun.
JUNE
30
88
—— — —
normal
mean daily temperature
mean daily
80
O
temperature
pollen shedding date
Figure 2.- Pollen shedding dates and mean
daily temperatures in 1947,
1948,
and 1949;
and "normal" mean daily temperatures (see
page 3 for derivation of normal curves).
-9-