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CONTENTS
Page
INTRODUCTION .... .. ................................ ........... 3
DEFINING THE BEST SEEDLING .. .................. ........... 3
SEEDLING QUALITY ....... .. ...................... ..............
Species Selection............ ......................... 3
Provenance Selection...................................4
Genotype Selection........... ............................ 4
Seedling Grade.............. ............................ 4
SEEDLING HANDLING .............................. ............. 5
Planting Date................................. ......... 6
NURSERY PRACTICES FOR PRODUCING QUALITY SEEDLINGS............. 8
Handling Seed to Produce Uniform Seedlings.................... 8
Practices for Producing Heavy Root Systems and
Large Diameters.............................................8
Practices for Controlling Seedling Height........................ 9
OPTIMUM USE OF NURSERY TECHNOLOGY............................ 9
LITERATURE CITED .................................................... 10
FIRST PRINTING 1.25M, DECEMBER 1984
COVER PHOTO. Successful artificial regeneration requires a combination of
quality seedlings and quality plantings. In the past, hand planters were
well supervised and seedling care was stressed more than speed of
planting. Two-man planting crews were sometimes used. One planter
would make the dibble holes and the other would carry the seedlings and
see that they were properly planted. Seedlings were sometimes carried in
buckets or trays to prevent drying of seedling root systems. In contrast,
speed of planting is stressed today while quality supervision of planters
may be lacking. Because large dibble holes take longer to make, planters
often request small seedlings which require smaller dibble holes. In order
to speed up the planting process, some planters will even strip lateral
roots from the seedling. In some cases, short-term convenience is placed
ahead of long-term reforestation goals.
Information contained herein is available to all persons
without regard to race, color, sex, or national origin.
GROWING THE "BEST" SEEDLING
FOR REFORESTATION 
SUCCESS
DAVID B. SOUTH and JOHN G. MEXAL
1
INTRODUCTION
C HARACTERISTICS of the "best" seedling depend upon the
objectives of the organization or individual buying or using the
seedling. As objectives change, the desirable physiological and
morphological traits of a "quality" seedling change. Factors that can
affect seedling traits include provenance, climatological factors,
planting site, time of transplanting, length of storage, method of
transplanting, and last but not least, the financial goals of the
organization or individual. The objective of this paper is to discuss
the factors that go into determining the best seedling and the
practices that might be used to grow such a seedling.
DEFINING THE BEST SEEDLING
A definition of the best seedling may vary from simple mor-
phological descriptions to elaborate physiological measurements.
However, the ultimate definition rests on successful establishment
and growth following outplanting. A working definition of "planting
stock quality" is as follows: "The quality of planting stock is the
degree to which that stock realizes the objectives of management
(to the end of the rotation or achievement of specified sought
benefits) at minimum cost. Quality is fitness for purpose (70)."
Therefore, a "quality" seedling will vary depending on manage-
ment objectives. Since management objectives of organizations
and individuals vary, so will the morphological, physiological, and
economical traits of the best seedling. The following is a list of
examples on how individual objectives can affect the definition of
the best loblolly pine seedling.
1. Individual: Tree planter paid for the number of seedlings
planted.
Objective: To plant seedlings quickly.
Definition: A short seedling with a small root system.
Benefits sought: The requirement of only a small dibble
hole means less time is required to plant each seedling. More
seedlings can be packed into seedling bag and therefore less
time is lost refilling bag.
2. Individual: Tree planter who rides a machine planter.
Objective: To place seedlings into mechanical fingers.
Definition: A tall seedling.
Benefits sought: To keep human fingers away from me-
chanical fingers.
1
Respectively, Assistant Professor, Forestry Research, Alabama Ag-
ricultural Experiment Station, and Head, Department of Horticulture,
New Mexico State University.
3. Individual: Private landowner who farms.
Objective: To plant marginal cropland to pine seedlings.
Definition: Free or inexpensive seedlings.
Benefits sought: Income for children; low capital outlay.
4. Individual: Planting contractor who is paid in part on
survival.
Objective: To plant seedlings quickly and so they will
live.
Definition: A short seedling with a 3- to 4-millimeter
root-collar diameter; a live seedling that will survive stress.
Benefits sought: High initial survival; to plant quickly.
5. Individual: Land manager of big paper company.
Objective: To plant X hectares and replant Y hectares
before spring.
Definition: 1,000 live seedlings per bale.
Benefits sought: Acceptable survival; to keep track of the
number of hectares planted by knowing how many bales
were used.
6. Individual: Land manager of better paper company.
Objective: To increase volume production per hectare.
Definition: Stem diameter greater than 4 millimeters,
shoot height less than 30 centimeters, prominent terminal
bud, numerous primary lateral roots, heavy root system,
good mycorrhizal infection of feeder roots, mature secondary
needles, $20-$30 per thousand.
Benefits sought: High survival, increased volume pro-
duction, shortened rotation, high internal rate of return.
It is apparent that desirable characteristics of a seedling can vary
with individual objectives. Therefore, for the purpose of this paper,
the objectives will be limited to two primary factors: survival and
growth.
SEEDLING QUALITY
Species Selection
Paramount to other management decisions is the selection of the
correct species to plant. The final product can dictate to a large
extent the species to be planted. For example, eastern white pine
(Pinus strobus L.) is preferred for manufacturing matchsticks.
Slash (P. eliottii Engelm.) and longleaf (P. palustris Mill.) pine are
used for turpentine production, while longleaf pine is also excellent
for poles. For sawtimber, loblolly (P. taeda L.), slash, and longleaf
pine are favored. Oak (Quercus spp.) and walnut (Juglans nigra L.)
are often favored for furniture. Virginia pine (P. virginiana Mill.),
eastern white pine, and Fraser fir (Abiesfraseri (Pursh) Poir.) are
often planted for use as Christmas trees.
If the objective is to maximize the production of softwood pulp-
wood in the South, then selection of the correct species is narrowed
to a few southern pine species. The selection of the best species to
plant is then dependent largely on the geographical region, the
climate, the incidence of various pests, and specific site charac-
teristics. Loblolly, shortleaf, longleaf, and slash pine make up 90
percent of the standing pine inventory (58). Virginia pine com-
prises 5 percent, while pond (P. serotina Michx.), pitch (P. rigida
Mill.), spruce (P. glabra Walt.), table-mountain (P. pungens
Lamb.), and sand (P. clausa (Chapm.) Vasey) pines make up the
remaining 5 percent.
Loblolly pine is by far the dominant pine species in the South
because it is adaptable to a wide range of sites and has a good growth
rate. However, loblolly pine is susceptible to fusiform rust and tip
moth attack, table 1. On most sites, loblolly pine will outperform
other species in both survival and growth (7).
TABLE 1. CHARACTERISTICS OF THE FOUR MAJOR SOUTHERN PINES (61)
CODE: E = EXCELLENT, G = GOOD, F = FAIR, AND P = PooR
Resistance to:
Species Seedling Fusiform Tip Growth Adaptability
Species quality rust moth rate
Loblolly G F P G Broad site range
Slash E P E G Glaze storm-
free areas
Shortleaf F-P E P F-P' Well-drained sites
Longleaf F E E F-P' Well-drained sites
'Growth rate dependent upon seedling quality.
Shortleaf pine is best adapted to well-drained or droughty sites
but is often characterized by relatively slow initial height growth.
This could partially be due to poor seedling quality. As shortleaf
seed is small, this trait combined with high sowing rates often
results in small, spindly seedlings. Reduced sowing rates can
improve seedling quality. Shortleaf is highly resistant to fusiform
rust but highly susceptible to tip moth and little-leaf disease on
poorly drained sites. Loblolly is usually preferred to shortleaf pine
except on extremely dry sites in the northern limits of the loblolly
pine range and where the risk of ice damage is severe.
The natural range of slash pine is almost completely delineated
by the glaze storm-free region of the South. This species favors
moderately to poorly drained soils. Morphological characteristics
of slash pine seedlings are excellent, however it is highly sus-
ceptible to fusiform rust. Because of the potential damage from ice
storms and fusiform rust, slash pine should be planted within its
natural range and on wet sites where it clearly outperforms loblolly
pine (56).
Longleaf pine is not limited by glaze storms but is confined for
the most part to the Coastal Plain. Seedling quality of longleaf pine
has often been poor due to small seedling diameters. Seedlings
require a critical root collar diameter to bring them out of the
"grass" stage. Small seedlings may stay in this form for 7 years or
more and can frequently succumb to brownspot infections. Once
out of the grass stage, height growth is excellent. Recent advances
in herbaceous weed control can shorten the grass stage (36).
Because of its excellent resistance to fire damage and fusiform rust,
longleaf pine may be the preferred species on dry sites where
problems with fire and fusiform exist.
Sand pine is an excellent example of a "minor" species out-
performing other species on particular sites. In the sand hills of
Florida, volume growth of sand pine was more than double that of
any other species (9).
Provenance Selection
Once the best species to plant has been selected, then it becomes
important to select the best provenance. The most conservative
approach is to use local sources. Generally that approach will
ensure adequate survival and growth. However, sources of wide
geographic origin are often planted to increase individual tree yield
with little or no loss in survival. Provenance trials are available for
many states, and although they may be limited to specific soil types
or locations, relative performance of divergent sources is illustrated
to the land manager. General seed source recommendations have
been developed for loblolly, longleaf, and shortleaf pines
(65,66,67,68,69). The conclusion is that seed from the southern
and eastern provenances perform better than local or more north-
ern sources. For example, coastal loblolly pine provenances gen-
erally outperform interior provenances. However, because of pos-
sible injury from ice damage, moving seed too far north can be
deleterious. Seed movement should be conservative if data are not
available for the specific seed sources and area.
Genotype Selection
Tree improvement in the South has developed to the point
where some organizations are producing second generation seed
capable of producing a 25 percent increase in volume production
over "wild" seed. Therefore, as long as the "improved" genotype is
adapted to the site, the best seedling will be an improved seedling.
However, if the improved seedling is not adapted for the site,
seedlings from wild parent trees adapted to the site may be the
best. For example, for marginal sites subject to drought in Texas,
wild, drought-hardy loblolly pine from Texas would likely survive
and grow better than improved loblolly pine from the Coastal Plain
of Louisiana.
Seedling Grade
Seedling grades for southern pines suggested by Wakeley (61)
were based upon diameter, among other factors. The grades for
slash and loblolly pines were: Grade 1 greater than 4.8 millimeters;
Grade 2 greater than 3.2 millimeters; Grade 3 less than 3.2 mil-
limeters (cull). It is noted that no southern pine nursery in the
South currently grades seedlings into three grades. Some nurseries
cull small and diseased seedlings before shipping but forest nurs-
eries in the South do not sell seedlings by grades as do some
nurseries in other regions of the United States.
There have been numerous studies conducted on the effects of
seedling grade on survival, figure 1. The general conclusion was
that planting seedlings with larger diameters increased survival. In
only a few cases did smaller seedlings have better survival. In one
case, it is believed lower survival resulted from the tree planters
not being able to get a large root system in a small dibble hole. In
another case, it is believed the shoot/root ratio was better for
smaller seedlings and therefore resulted in better survival during a
summer drought (59).
Several seedling grade studies exist that report volume pro-
duction 10 to 34 years after planting. The general conclusion from
these indicates Grade 1 seedlings produced greater volume
through increased survival and growth, figure 2. On the average,
volume production was 25 percent greater for Grade 1 seedlings
than for Grade 2 seedlings. Although these data suggest that large
increases in forest productivity can result from planting Grade 1
seedlings, most loblolly pine seedlings produced in the South are
Grade 2 seedlings. A cursory survey of 53 nurseries by the senior
Survival, pct.
100
49.31
y = 91.7-
x
r2= .81 ((= .005)
90
80-
70- "
60
1.0 2.0 3.0 4.0 5.0 6.0 7.0
Diameter, mm
FIG. 1. Relationship between seedling diameter at time of lifting 
and
field survival. Data represent a compilation of studies for loblolly
and slash pine. (1,6,10,13,14,22,39,40,42,52,60)
author in 1982 indicated that 44 nurseries were producing less than
20 percent Grade 1 seedlings. Few nurseries produced a high
proportion of seedlings with the following characteristics: stem
diameter greater than 4 millimeters, shoot height less than 30
centimeters, prominent terminal bud, mature secondary needles
(greater than 8 centimeters) at the terminal, numerous primary
lateral roots, heavy mycorrhizal infection of feeder roots, and
average root dry weight greater than 0.8 gram.
While the importance of seedling grade is recognized, the fact
that so-called cull seedlings have performed as well as quality
seedlings on occasion has also been recognized although not as well
documented (61). The reason for this stems from a strong inter-
action between seedling height and site as well as an inability to
identify the seedling's "physiological quality." On sites with heavy
vegetation, taller seedlings often outperform shorter seedlings, but
on droughty sites, shorter seedlings with lower transpirational
surface area often outperform taller seedlings, table 2. On moist
sites, seedling height had no effect on either survival or first-year
height increment. However, on the droughty site, seedlings with
the larger transpirational surface areas not only suffered greater
summer mortality, but also grew less the first season. On this site, it
appears that shorter seedlings may surpass taller seedlings with
another growing season. Therefore, the correlation between sur-
vival and shoot/root ratios (dry weight) or height/diameter ratios
will be low for sites and years when moisture is abundant and high
when moisture is limited.
50 
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Seedling grade
FIG. 2. Relationship between seedling grade at time of planting and
field survival and growth 10 to 34 years later. Represents a com-
pilation of data for loblolly and slash pine for studies: 30-34 years
old (62); 15 years old (44); 13 years old (6); 13 years old (48); and 10
years old (21).
Wakely (61) stated that no test had been developed to identify
the physiological qualities of southern pine seedlings in advance of
planting (61). Research during the past 30 years has progressed
little in this regard. Seedling quality reflects the integration of a
multitude of physiological and morphological characteristics.
Taken in mass, seedling quality attributes such as root growth
potential, height/diameter ratio, root weight, root starch concen-
tration, leaf osmotic potential, mitotic index, root specific gravity,
diameter, height, impedance ratio, chilling hours, mycorrhizal
index, and shoot/root ratio (dry weight) may ultimately determine
seedling performance. However, considering the complexity of the
seedling, the planting site, and seedling-site interactions, a single
factor for grading seedling quality may never be fully satisfactory
(38).
SEEDLING HANDLING
Several factors can alter the quality of seedlings produced in the
nursery. These include planting date, storage, and handling. Some
factors are beyond the nurseryman's control and therefore must
also be of concern to the reforestation forester.
TABLE 2. THE EFFECT OF SEEDLING SIZE ON FIRST-YEAR SURVIVAL AND HEIGHT GROWTH OF 
LOBLOLLY PINE
PLANTED ON DIFFERENT SITES IN OKLAHOMA (2)
Height: Site classification
Initial seedling diameter Wet 
Mesic Droughty
Height Caliper ratio Survival Height 
Survival Height Survival Height
growth 
growth 
growth
cm mm Pct. cm Pct. cm 
Pct. cm
13 4 33 93 22 93 15 
48 16
20 5 40 95 23 93 18 
47 13
31 6 52 95 21 96 16 
40 8
Performance, pct.
100
Volume production
(pct. of maximum)
90 c
Survival
80
70
60
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Planting Date
Historically, most southern foresters consider the "prime" plant-
ing season to be from mid-December to mid-March or the first of
April. Planting during this time generally ensures high survival and
growth, figure 3. Early planting (prior to December 15) is usually
riskier for survival, but height growth is usually greater. For late
planting (after march 15), survival can equal that for early planting,
but growth is reduced due to the shortened growing season.
Freshly lifted seedlings. Wakeley (61) demonstrated the effect of
planting date on first-year survival of major southern pine species.
Survival was near 90 percent for freshly lifted seedlings planted
between November 9 and March 1. Dierauf (12) examined early
and late planting of loblolly pine seedlings in Virginia over 3 years
and reported similar findings, table 3. After three growing seasons,
survival of early planted seedlings was lower 1 year, but height
growth was greater for early plantings for all 3 years. Mexal and
Morris (31) found similar results, table 4. November plantings can
prove successful when compared to March or April planting. There
are operations in Georgia (20) and Florida that routinely suc-
cessfully plant wet sites as early as the end of October.
For early planting to be successful, soil moisture must be ade-
quate at time of planting and the coming winter must not be too
severe. For example, Bilan (5) reported that loblolly seedlings
planted in east Texas on November 11 had twice the root growth of
seedlings planted in January. During this period, soil moisture was
adequate and the daily minimum temperature was often above 0?C.
Bilan stated that, "Since pines with well developed root systems
have a much better chance to survive dry spells than do the pines
with superficial root systems, an early planting is recommended
particularly for regions experiencing late spring or early summer
droughts." However, the advantage of early planting will be less in
regions where severe freezing temperatures are more common. In
Virginia, Dierauf (15) stated that seedlings planted after the worst
of the winter weather is over may have a higher chance of survival
than seedlings planted in December. During severe winters,
seedlings planted on cleared sites in December would be subjected
to desiccation resulting from frozen ground and exposure to high
winds.
Relative
performance, pct.
and losses from one nursery (apparently associated with long
TABLE 3. SURVIVAL AND HEIGHT AFTER THREE
GROWING SEASONS IN VIRGINIA (12)
Lifting and 1971 1972 1973
planting date Survival Height 
Survival Height Survival Height
Pct. m Pct. m Pct. m
November 1....... 77* 1.65 92 1.58* 88* .85*
March 15 ......... 96 1.58 92 1.34 73 .64
*Indicates differences are significant at the 1 percent level.
TABLE 4. THE EFFECT OF PLANTING DATE ON
SURVIVAL AND HEIGHT TWO YEARS
AFTER PLANTING (31)
Location Lifting date Planting date Survival Height
Pct. m
Alabama ....... October October 53 0.58
November November 84 .79
January January 75 .81
November January 69 .96
March April 46 .53
Arkansas ....... November November 76 .79
January January 77 .74
March March 78 .76
November January 50 .70
N. Carolina .... November November 97 1.24
January January 96 1.10
November January 95 1.01
Successful planting outside the prime planting season can vary
with seed source (4). One progeny survived transplanting regard-
less of timing (December 13 to June 3). However, two other
progenies could not be successfully planted until after January 27,
and one had to be planted before June 3. This illustrates the
importance of understanding seed lots used in regeneration. Some
lots may have a broad planting season while others may have a
relatively narrow season. This can be an important consideration if
the regeneration forester wishes to extend the planting season.
Many foresters are already utilizing the late season, but few have
considered the early season. Management plans should consider
both seasons to ensure completion of planned regeneration ac-
tivities. However, the forester should implement research results
slowly since results from one region, or one climatic year, may not
be reproducible somewhere else or in another year. Technology
transfer should occur gradually to maximize gains with minimum
losses.
Stored seedlings. Storage of seedlings at temperatures from 1
?
C
to 3?C is a necessary "evil" and should be used judiciously. The
success of cool storage is dependent on several factors, including
seed source and length of chilling before lifting (18,19). For exam-
ple, two seed sources from Arkansas and Oklahoma differ dramati-
cally in their cool-storage capabilities, figure 4. The more northern
source (McCurtain County, Oklahoma) is less sensitive to periods
of storage than the southerly source (Polk County, Texas). Both
sources stored well after receiving chilling through December, but
the northern source was affected less by storage prior to a De-
cember 13 lifting date. For greatest success, storage of seedlings
should be minimized until the chilling-hour requirement for that
source has been reached. Weyerhaeuser Co. currently stamps
seedling bags with an expiration date dependent upon the date
lifted and the number of chilling hours accrued. If loblolly seed-
lings are not planted shortly after lifting, then the seedling "qual-
ity" is a function of the chilling hours received. Failure to monitor
chilling hours can result in reduced seedling survival, especially for
years with warm fall weather. The fall of 1982 was unusually warm
Dec. Jan. Feb. Mar.
Planting month
Apr.
FIG. 4. The effect of lifting date and time in storage on survival of two
seed sources outplanted in Arkansas (from Dunlap and Mexal,
unpublished).
storage of seedlings with insufficient chilling) exceeded $220,000
(37). For those nurseries that must store seedlings, monitoring
chilling hours and storing accordingly will improve quality.
Planting quality. Many seedlings in the South are planted by
hand. However, it is generally believed that machine planted
seedlings perform better than hand planted seedlings. This could
be a result of the machine being able to prepare a deeper planting
hole as well as a more uniform seedling placement and soil packing,
with less root exposure. In addition, machines do not tire and
planting consistency at the end of the day should be the same as at
the beginning. In one comparison, mean survival was 20 percent
higher for sand pine seedlings planted by machine compared to
dibble-bar (28). However, skips resulting from machine planting
can average above 10 percent (20), and in some plantings can range
as high as 20 to 30 percent (71).
Survey data from one company in Alabama suggest that super-
vision and speed of hand planting can affect seedling survival (34).
For two planting seasons, company crews (paid by the hour)
averaged 87 percent survival while contract crews (paid by the
seedling) averaged only 81 percent survival. Seedlings planted
with maximum care averaged 92 percent survival. Obviously,
planting quality is directly proportional to the quality of
supervision.
Factors such as available soil moisture, competing vegetation,
planting depth, and quality of planting can strongly influence
seedling performance. For example, for sand pine seedlings stored
in unrefrigerated sheds, survival is dependent upon time in storage
and level of weed competition, figure 5. For planting on prepared
sites, seedlings could be stored unrefrigerated for 8 days with little
loss in survival. However, on wooded sites survival was almost 30
percentage points lower for stored trees. Apparently, storage for 8
days reduced the vigor of seedlings to the point that they were
unable to compete with established vegetation.
Planting quality can be influenced by seedling handling and
exposure, planting depth, j-rooting, and root twirling. No matter
how slight, mistreatment of the seedling can result in significant
volume loss at the end of rotation. Mullin (35) reported red pine
stand volumes were reduced 14 percent after 20 years simply by a
Survival, pct.
10l0 - _ ____ - w a
r
Prepared sites
Wooded sites
Survival, pct.
100
90-
80 -1
70
60 Si
6 - 51$- -
I I I
0 1 2 3
Age, years
FIG. 5. The effect of unrefrigerated storage on survival of Ocala sand
pine planted on two sites on January 21 (9).
change in planting crews, which infers a change in quality. Mexal et
al. (32) found a loss of up to 1 meter ofsite index (S.I.
25
) due to poor
planting. The loss of site index was most pronounced on lower site
lands. This is to be expected because moisture is limiting on these
sites much of the year and root deformation compounds the prob-
lem.
Much root deformation can be explained by deep planting in a
shallow planting hole. Tree planters tend to plant deep without
considering either the length of the dibble bar or the length of the
taproot. In addition, making a sufficiently deep planting hole to
avoid root deformation usually requires more time and results in a
reduction of pay for planters paid by number of seedlings planted.
Planting seedlings to a standard depth would alleviate much de-
formation. However, this recommendation should not be rigid.
Deep planting without deformation can be advantageous, figure 6.
Seedlings should be planted as deep as a dibble bar will allow on
droughty soils to ensure high survival and growth, but on heavier
soils or soils that drain slowly, deep planting decreases survival
accompanied by a concomitant loss of height advantage (27). Sands
or loams can be planted deep (half of stem buried), but clay-loams
or heavier soils should be planted only 2-3 centimeters above the
root collar (43). Planting too shallow, of course, can be detrimental.
A survey of operational plantings found shallow planting to be
correlated with reduced survival in three out of four operational
districts (72).
It is doubtful that desirable traits of a quality loblolly pine
seedling will be the same throughout the South. Traits that result in
high survival and rapid growth may vary by region, site, and
planting method. For example, seedlings planted in drought-prone
Texas will require a genotype adapted to the area as well as a short
seedling with a low height/diameter ratio. Seedlings planted in the
Coastal Plain of North Carolina could be taller and perform as well
as higher quality seedlings due to lower average water deficits.
Seedlings produced in Virginia may need to withstand long-term
cold storage due to weather related delays in planting, whereas
seedlings in Florida may need to be planted rapidly due to an
inability to store well for most years. On Coastal Plain sites that are
easy to plant, a Grade 1 seedling may be desirable for planting
either by machine or by hand. However, Grade 2 seedlings may be
preferred for hand planting on sites with fine textures in the
Piedmont where deep dibble holes are difficult to make.
tored I day
tored 8 days
FIG. 6. Effect of planting depth on survival of southern pine seed-
lings. Sand to sandy-loam (27)-Grade 2 seedlings; well drained
clay (43); poorly drained clay (53); poorly drained silt (53).
Most nurserymen in the South sow for one density with one or
two mixed lots from the seed orchard. However, they provide only
one or two choices of seedlings for outplanting. If the land base is
small and uniform, one type of planting method is used, and
planting is confined to the optimum planting season, this may be
acceptable. However, if the land base covers a wide range of sites in
several geographic provenances, the planting season is extended
into the fall, and several types of planting methods and crews are
used, then it would be better if the nurserymen could provide a
range of seedling types. This can be accomplished by sowing
various genotypes and at different densities.
NURSERY PRACTICES FOR PRODUCING
QUALITY SEEDLINGS
There are a number of cultural practices available to the
nurseryman who wishes to improve the quality of his nursery stock.
However, some practices may increase production costs and there-
fore should be prescribed according to region, site, and planting
method. When choosing cultural practices, the nurseryman must
weigh the economics and the anticipated survival and volume
growth of each treatment. It should be remembered that cheap and
inexpensive are not necessarily synonymous when the entire cycle
of a plantation is considered.
Handling Seed to Produce Uniform Seedlings
A goal of nurserymen is to produce a uniform crop of seedlings.
However, a broad range of seedling morphologies is usually pro-
duced which often includes a number of cull seedlings. This is
largely a result of uneven seed germination. Seed that are the first
to germinate usually produce seedlings with the largest diameters,
while culls usually arise from seed that germinate last. Therefore,
the diameter distribution will be narrow for seed that germinate
over a short period (a few days) and wide for seed germinating over
several weeks. Seed handling is the major factor that determines
the length of time for germination to occur.
There are several practices that will help reduce the production
of cull seedlings and narrow the distribution of diameters pro-
duced. Sowing empty seed along with full seed will cause many
seedlings to grow closer to one another than need be. With loblolly
pine, this can be avoided by soaking seed in water and removing
the "empty seed" that float. Sowing seed with high germination
rates (greater than 95 percent) will help produce uniform seedlings.
Sizing seed is important to produce uniform seedlings. In gen-
eral, large seed germinate more quickly than small seed and thus
produce larger seedlings (16). Sowing by seed size therefore results
in more uniform germination.
Nurserymen quickly realized the importance of seed stratifica-
tion for producing uniform seedlings. For species like loblolly pine,
stratification can reduce the period required for germination by
approximately three-fourths (3). The length of stratification can
determine how rapidly emergence occurs.
Improper covering of seed during sowing can result in an erratic
stand of seedlings. If a mulch is used, a uniform application depth is
desired. Too sparse or too deep a covering can affect seedling
emergence and growth. If no mulch is used, seed should be sown at
a uniform soil depth.
Sowing by family will also increase seedling uniformity. Wasser
(64) showed that seed from different families can germinate at
differing rates. Subsequently, seed from a slow germinating family
developed into seedlings with smaller diameter when sown in
mixed lots. Average seedling diameter was more uniform when
seed were sown by family.
Precision sowing of seed will increase seedling uniformity. Vari-
ous sowers currently used in forest nurseries are not precision but
are actually drills that often distribute seed in clumps. Cull seed-
lings can often arise from seed sown too close together. Precision
sowers have been developed that will sow one seed at a time. This
reduces clumping of seed and results in a reduction in the pro-
duction of culls. One study from New Zealand reported that
seedlings resulting from precision sowings produce higher initial
volume when outplanted (57).
Practices for Producing Heavy Root Systems
and Large Diameters
A goal of nurserymen is to produce seedlings with large dia-
meters and heavy root systems. If properly planted, such seedlings
will often outperform smaller seedlings of equal height.
Competition for water, light, and nutrients by weeds can greatly
affect seedling morphology. Therefore, to produce large-diameter
seedlings, the nurseryman must keep weed populations under
control. This can be achieved with use of integrated weed control
practices in combination with selective herbicides (45).
High soil bulk density will inhibit seedling root growth
(33,73,23). Mitchell et al. (33) have shown that root mass of loblolly
pine in a sandy loam soil can be reduced by 23 percent when bulk
density is increased from 1.2 to 1.6 grams per cubic centimeter. To
help avoid compacting the soil, nurserymen should avoid working
the soil when wet and should keep tractor paths confined to the
alleyways. Subsoiling, wrenching, and incorporation of organic
matter can help reduce soil bulk density. Brown and Pokorny (8)
have shown that bulk density can be decreased by 0.3 gram per
cubic centimeter when 5 centimeters of pine bark is incorporated
into the top 15 centimeters of soil.
Spacing between seedlings is another major factor influencing
seedling morphology. Seedlings grown close together (at high
densities) often have small diameters and light root systems. Opti-
mum seedling spacing is dependent on desired seedling diameter,
fertilization, soil moisture, drill spacing, date of sowing, and eco-
nomics. In New Zealand, 5-centimeter spacings have proven de-
sirable with "single" 13-centimeter drills. Mexal (30) suggests an
optimum growing space per seedling of 50 square centimeters for
loblolly pine (and prefers offset "double" drills with 5.1-centimeter
minimum distance between seedlings).
Early sowing will result in increased seedling diameters. In the
past when fertilization was practiced less, nurserymen often sowed
early. In 1957, sowing by the middle of April was considered late
for nurseries in Florida and Georgia (17). At the Ashe Nursery in
Mississippi, loblolly pine was sown from March 23 to 28 in 1966 (as
compared to April 25 to May 6 in 1983). Currently, the Tilghman
Nursery in South Carolina routinely sows in March. However, to
keep seedlings from growing too tall, many nurserymen have
delayed sowing until the middle of April or the first of May. While
sowing late may limit height growth, it also adversely affects
seedling biomass. Data from Georgia (46) indicate that for each day
sowing is delayed, a 1.2 percent decrease in seedling weight occurs
by mid-winter. When height growth is controlled by other means,
sowing early can help reduce the production of cull seedlings.
Monitoring soil fertility and making proper fertilizer and organic
matter additions are essential if quality seedlings are to be pro-
duced on a continuing basis. Inadequate fertilization can result in
undersized seedlings while overfertilization of certain elements
can produce toxicity symptoms. Wide fluctuations in soil acidity
levels and soil nutrient levels can be avoided by evaluating changes
in soil nutrient values over time. A soil testing program for forest
nurseries in the Southern Coastal Plain has been established to
help nurserymen with fertility management of their soils (47).
An interaction between seed spacing and nitrogen fertilization
exists. The lower the density or the greater the nitrogen per plant,
the larger the seedling. In general, seedlings grown at close spac-
ings respond proportionately more to nitrogen fertilization than
seedlings grown at wider spacings. Switzer and Nelson (54) found
that maximum yield for loblolly pine (in terms of the percentage of
seedlings with root collars greater than 3 millimeters) could be
achieved with an application of about 160 milligrams of N per plant.
Early formation of mycorrhizae is important if seedlings are to
benefit from fertilization. This can be especially important for new
nurseries or new seedbeds where pine seedlings are grown for the
first time. Even with high levels of N, P. K, and Ca in the soil,
loblolly pine seedlings in noninfested fumigated soil may not grow
appreciably until ectomycorrhizae form (26). Since mycorrhizae
can have an important impact on both seedling size and subsequent
outplanting performance, nurserymen should be aware of practices
that may adversely affect the formation of mycorrhizae 
(25,41,49).
If the planting site is adverse, then the species of mycorrhizal
symbiont can be important. When planted on coal spoils, seedlings
inoculated with Pisolithus tinctorius (Pers.) Coker and Couch have
performed better than seedlings with other naturally occurring
ectomycorrhizal fungi (24,63). Techniques involving fumigation,
inoculation, and fertilization have been developed for tailoring
seedlings with this fungal symbiont (11).
Diameter growth of seedlings can be inhibited by extended
periods of anaerobic soil conditions. To avoid such conditions,
nurserymen should not allow the soil to remain in a saturated
condition. Nurserymen can help prevent this from occurring by
keeping infiltration rates adequate (above 8 centimeters per hour)
and by not over-irrigating. Infiltration rates will be low in areas
with high bulk density, plow pans, high water tables, and high silt
or clay content. Some root diseases are more likely to occur in areas
with poor infiltration.
Control of root diseases is important to the production of quality
seedlings. Nurserymen should be aware of the environmental
conditions which favor development and the cultural treatments
which help prevent development of various diseases. Maintaining
an adequate supply of soil organic matter, keeping soil pH levels
low, keeping infiltration rates high, using a mulch to keep bed
temperatures moderate, and soil fumigation are some cultural
treatments that can be used to control diseases (51).
Practices for Controlling Seedling Height
There are three methods commonly used for regulating seedling
height: (1) moisture stress; (2) root pruning; and (3) top pruning.
Moisture stress can be used to slow terminal elongation. Nursery-
men often reduce or stop irrigation of seedlings in August or
September inan effort to reduce seedling height growth. Stransky
and Wilson (50) found terminal elongation ofloblolly pine slowed at
2 bars of soil moisture tension. Unfortunately, rainfall in the fall
may thwart the nurseryman's efforts to stress seedlings. Seedling
moisture stress may therefore be imposed by root pruning and/or
wrenching. One study on loblolly pine indicated a single under-
cutting and wrenching resulted in a significant improvement in
shoot/root ratio as well as a significant improvement in field survival
(55).
For some nurseries with fine-textured soils and poor structure,
undercutting or wrenching may be difficult to practice. In addition,
height growth at some nurseries may be quite variable (as a result of
sowing a mixture of families or when germination is spread over
several weeks). Therefore, top pruning of seedlings may be re-
quired to keep seedlings from being unbalanced. If top pruned in
August and only succulent tissue is cut, seedlings may recover and
form new terminal buds by December. However, if top pruning
occurs late and woody tissue is cut, a terminal bud may not form
and auxiliary buds may develop slowly. Regardless of when top
pruning occurs, growth of lateral roots may be reduced as the
seedling channels its energies into repairing the severed shoot.
OPTIMUM USE OF NURSERY TECHNOLOGY
There are several technological advances presently available to
nursery managers but which are not commonly used. Such ad-
vances include computer generated maps for use in land shaping,
tile drainage, automatic calibration of pesticide applicators, auto-
matic guidance of tractors, ultra-low-volume applications of herbi-
cides, automatic irrigation systems, monitoring of pesticide levels
in soil, foliar nutrient analyses, uniform application of lime and
fertilizers, containerization, mycorrhizal inoculation, sowing by
family, monitoring xylem water potential, use of soil tensiometers,
monitoring carbohydrates in roots. continuous recording of
weather information, precision sowing, monitoring seed efficien-
cies, modifying soil chemical and physical properties with organic
amendments high in lignin, automatic alignment devices for lateral
root pruners, high flotation/low compaction spray equipment,
subsoilers, use of microcomputers, monitoring seedling mor-
phology, and monitoring seedling outplanting performance.
There are four basic reasons why various technological advances
are not commonly used in forest nurseries. The first is a lack of
available data to indicate an economic benefit. For example, pur-
chasing an automatic pesticide calibration unit for $3,000 may not
be justified economically if data on pesticide overuse are not
available. The second reason involves technological advancements
which are proven to be uneconomical once the data are collected.
The third reason deals with operating under budget restraints
which do not allow taking advantage of technological advances.
Purchasing a precision sower at a 20-million seedling nursery for
$32,000 to improve seed efficency by 2 percent (and thereby
increase annual revenues by $8,000 by selling an additional
400,000 seedlings at $20 per thousand) may not be possible if the
governmental agency is operating under an austerity budget. The
fourth reason involves a lack of education due to insufficient econ-
omic analysis. The economic return for practices such as precision
sowing and sowing by family are high, but nurserymen and nursery
supervisors have often not provided the needed analysis. For
example, many nurserymen are presently using much of the sow-
ing technology developed 50 years ago when seed were from wild
sources. Today, with the present net value of improved seed worth
1 cent per seed or more, technological improvements in sowing
practices can be easily justified if seed efficiencies can be improved.
For example, if an organization can increase seed efficiency by 6
percent and thereby plant an additional 3,000 hectares with im-
proved seedlings (at 15 percent gain), the resulting increase in
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In addition, large economic benefits can also result from ap-
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11