Hybrid Poplar Production 1998 - University of Nevada Cooperative ...

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Fact Sheet 05-25
Hybrid Poplar Production 1998- 2003 in Eureka and Churchill Counties
Jay Davison, Area Plant and Soils Specialist
William W. Riggs, Eureka County Extension Educator
Introduction
Poplar is a generic term used to describe trees in the
Populus genus. The genus includes cottonwoods,
and aspen. Hybrid poplars are trees that are
developed by crossing two different species of
poplars. The most common poplars used to develop
crosses include the eastern and black cottonwood,
aspen, the Lombardy, European black, balsam and
white poplars. The crossing often results in trees
that display the best traits of each parent species.
They are usually hardier, grow faster, and are more
widely adapted than either parent. The various
hybrid poplars varieties are known as accessions
and they are numbered. One of the most successful
accessions is OP-367 which was developed by
crossing eastern cottonwood (Populus deltoids)
with European black poplar (Populus nigra).
Poplars developed from these crosses are commonly
known as DN crosses. The other accessions used in
the trial (15-029, 50-197, 52-225) are known as TD
crosses because they are developed from the black
cottonwood (Populus trichocarpa) and eastern
cottonwood (Populus deltoids).
Uses for poplar trees
Poplar trees are grown for a wide variety of uses.
The uses include: home landscaping, environmental
cleanup, and production of paper, wood, and
biomass products. During the late 1990’s, large
hybrid poplar tree plantations were established in
the Northwestern United States for the production
of pulpwood for paper mills. However, since that
time the market value of hybrid poplar pulpwood
has declined dramatically. As such, new uses for
poplar products are being developed. These uses
include: saw logs used to make furniture frames,
pallets, wood trim, and core materials that are
overlain with veneers. Poplar wood is being used to
produce plywood, oriented strand board (wafer
board) and laminated strand lumber (LSL) which is
used for beams and headers. Current testing is
evaluating hybrid poplars as a source of bio-fuels to
produce energy.
Nevada Trial Descriptions
Cooperative Extension faculty initiated two hybrid
poplar survival and production trials in 1998 and
1999. The first trial was established in Diamond
Valley, north of Eureka and the second on the
Newlands Agricultural Experiment Station in
Fallon, Nevada.
The Diamond Valley trial was planted on June 11.
1998. The trial consisted of 100 trees each of three
accessions for a total of 300 trees. The accessions
planted at the Diamond Valley site included OP-
367, 50-197, and 52-225. Each accession was
replicated five times. The trees were planted as
cuttings approximately 8 inches long and 3/8 inch in
diameter. They were planted on eight foot spacing
within and between rows. The cuttings were planted
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with one bud showing above the soil line and all
buds facing up. They were irrigated using drip
irrigation. The trees were protected from grazing
deer by 48” tall growth tubes. An active
fertilization, weed and rodent control program was
established at the same time to maximize growth of
the trees.
The Fallon trial was established on April 27, 1999
with the planting of 294 (98 each accession) trees.
The accessions planted in Fallon included OP-367,
50-197, and 15-029. The trees were planted on five
foot spacing within and between rows. Each
accession was replicated seven times. They were
planted in the same fashion as the Diamond Valley
trial. The Fallon trees were irrigated using flood
irrigation on the same schedule as the adjacent
alfalfa (approximately every 2 weeks). Weeds were
controlled using Roundup® and mechanical
methods. No fertilizer was applied. In April of
2002, ten trees of each accession were dug using a
24” tree spade and moved approximately 100 yards
to test the ability of the trees to withstand
transplanting as potential landscape stock.
The trees were thinned by removing every other tree
April of 2003. The purpose of the removal was to
increase the tree spacing and determine biomass
production after four years. The total green weight
of each accession was recorded during the thinning
process.
Results -Diamond Valley Trial
The planting costs for each tree on the Diamond
Valley site are displayed in table 1.
Table 1. Cash costs per hybrid poplar trees planted
in Diamond Valley, Nevada on June 11, 1998.
Input
Cost
Trees $0.20
Tree shelter & stakes $3.16
Drip irrigation $2.00
Labor $2.10
Total cash cost/tree $7.46
The trees begin budding on June 25, 1998, and by
the end of July, the trees were beginning to grow
out of the tops of the tree shelters that were 4 feet in
height. The irrigation to the trees was reduced by
approximately 50 percent beginning the first of
September in an attempt to “harden off” the trees
for winter. The first killing frost occurred on
September 19 th when the temperatures dipped to 27
degrees Fahrenheit. The irrigation system was then
shut down to avoid damage to the system. The
survival and production evaluation was completed
on October 12, 1998. The survival percentage was
in excess of 99% with only two trees failing to grow
out of the 300 planted.
The production evaluation was limited to
determining the average tree heights at the end of
the first growing season. Table 2 is the average tree
height of the three hybrid poplar accessions planted
in Diamond Valley during June 1998 and measured
during October 1998.
Table 2. Average first year tree heights of three
hybrid poplar accessions planted in Diamond Valley
in 1998.
Accession
Ave. Tree Heights
(ft)
OP-367 4.5
50-197 4.4
52-225 4.5
Irrigation of the trees planted in Diamond valley
resumed in May of 1999. The vast majority of the
top growth of the trees winterkilled. By the October
1999 evaluation, most of the trees had sprouted
from the roots but were considered a loss. The
project was abandoned that year.
Results-Fallon Trial
The planting costs for the Fallon trial were much
lower than that experienced in Diamond valley. No
tree shelters or drip irrigation supplies were
required as the trees were flood irrigated and no
deer were present. The planting technique was also
less labor intensive as the only action required was
to press a 3/8” hole in the soil and press the cutting
into the hole. Table 3 is the estimated cash cost of
planting hybrid poplars in Fallon

Table 3. Cash cost per hybrid poplar tree planted in
Fallon, Nevada on April 27, 1999.
Input
Cost
Trees $0.20
Labor $0.50
Total cash cost/tree $0.70
The trees were evaluated for survival and
production in November of 1999. The information
collected included the number alive, and the height.
Table 4 displays the results of the first year
evaluations.
Table 4. Average first year survival percentage, and
tree height for three hybrid poplar accessions
planted in 1999 in Fallon, Nevada.
Accession Survival
(%)
Tree ht.
(feet)
OP-367 100 4.4
50-197 99 4.0
15-029 94 4.6
The trees fared well in the winter of 1999-2000 with
only 1 additional death and rapid growth occurring
with all accessions. Table 5 displays the evaluation
information collected for the 2000 growing season.
Table 5. Average two-year survival percentage, tree
height, three hybrid poplar accessions planted in
1999 Fallon, Nevada.
Accession Survival (%) Tree ht. (feet)
OP-367 100 12.3
50-197 99 11.0
15-029 93 11.8
Tree survival continued to be excellent over the
winter of 2000-2001 with only one additional death.
By the fall of 2001, the trees were large enough to
begin collecting data on tree diameters one foot
above the ground. Table 6 displays the evaluation
information collected for the 2001 growing season.
Table 6. Average three-year survival percentage,
tree height, and diameter for three hybrid poplar
accessions planted in 1999 in Fallon, Nevada.
Accession Survival (%) Tree ht
(feet)
Tree diam.
(inch)
OP-367 100 26.1 2.9
50-197 99 20.8 2.5
15-029 93 19.2 2.0
Tree survival, heights and diameters were again
recorded following the 2002 growing season. No
additional trees had winterkilled and the growth rate
continued to be exceptional. Table 7 presents the
results of the 2002 growing season.
Table 7. Average four-year survival percentage, tree
height, and diameter for three hybrid poplar
accessions planted in 1999 in Fallon, Nevada.
Accession Survival
(%)
Tree ht
(feet)
Tree diam.
(inch)
OP-367 100 37.2 4.2
50-197 99 28.5 3.4
15-029 93 26.7 2.8
The greenwood biomass from each accession was
determined in April of 2003 by cutting and
weighing every other tree in the plantation. The
data was converted to average weight per tree
(green weight) in order to calculate different
yields/acre based on tree spacing. Table 8 is the
average tree weight from the 4-year-old stand
growing in Fallon and tons per acre dry weight on 5
X 5 spacing. The moisture percentage of the
harvested trees is assumed to be 50%.
Table 8. Average hybrid poplar biomass production
after 4 years by tree and per acre with 5’ X 5’
spacing, assuming 50% moisture content of the
harvested trees.
Accession
Ave.
lbs/tree
(green wt)
Ave.
tons/acre
(dry wt)
OP-367 63.1 27.4
50-197 44.9 19.5
15-029 47.9 20.8

Discussion
The hybrid poplar trees planted in Eureka were a
complete failure as over 98% died the first winter.
Hybrid poplars are grown in climates colder than
Eureka throughout the United States and the authors
speculate that the tree shelters remained on the trees
too long and were irrigated too late in the season
which delayed the onset of dormancy. Because of
the abnormal warmth, provided by the shelters the
trees failed to go dormant before winter
temperatures dropped into the killing range. The
trial was not repeated.
The Fallon trial was much more successful with
four-year mortality ranging from a low of 0 percent
to a high of only 7 percent. The accession OP-367
averaged 9.3 feet of growth per year, while 50-197
and 15-029 grew at 7.1 and 6.7 feet per year
respectively. The growth in diameter was less
impressive due to competition for light and space
resulting from the 5’ by 5’ spacing.
Resources used to develop this fact sheet
Blatner, K. A., Johnson, J.D. and Baumgartner, D.
M. (Eds), 2000, Hybrid Poplars in the Pacific
Northwest: Culture, Commerce, and Capability.
Symp. Proc. Cooperative Extension, Washington
State University. Pullman, Washington.
Bowersox, T.W., Blankenhorn, P.R., and Murphy,
W.K. 1979. Heat of combustion, ash content,
nutrient content, and chemical content, of populus
hybrids. Wood Science. 11:257-262.
Leavengood, S. and Reeb, J. 1997. Product and
Marketing Opportunities for Hybrid Poplar Wood in
Oregon. EM 8667. Oregon State University
Extension Service. Corvallis, Oregon
Mater Engineering. 1998. Marketing Study for a
Multi-Region Plantation Hybrid Poplar Project.
Mater Engineering Ltd. Corvallis, Oregon
The biomass produced by the trees was comparable
to that experienced by hybrid poplar trees growing
in the Northwest. Accession OP-367 averaged 6.8
tons per acre per year. Accession 50-197 and 15-
029 averaged 4.8 and 5.2 tons per acre per year over
the four-year growth period.
The hybrid poplar trial is continuing in Fallon.
Results will be updated as the data is developed.