United States

Department of

Agriculture

Forest Service

Southern

Research Station

General Technical

Report SRS–52

Guidelines for Producing

Quality Longleaf Pine Seeds

James P. Barnett and John M. McGilvray
The use of trade or firm names in this publication is for reader information and

does not imply endorsement by the U.S. Department of Agriculture of any

product or service.

This publication reports research involving pesticides. It does not contain

recommendations for their use, nor does it imply that the uses discussed here

have been registered. All uses of pesticides must be registered by appropriate

State and/or Federal agencies before they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, desirable

plants, and fish or other wildlife if they are not handled or applied properly. Use

all herbicides selectively and carefully. Follow recommended practices for the

disposal of surplus pesticides and their containers.

June 2002

Southern Research Station

P.O. Box 2680

Asheville, NC 28802

The Authors

James P. Barnett is a Project Leader, U.S. Department of Agriculture, Forest

Service, Southern Research Station, Pineville, LA 71360; John M. McGilvray,

Biological Technician (retired), USDA Forest Service, Southern Research

Station, Pineville, LA.

Cover: Dewinged longleaf pine seeds.

Photo by Eric Vallery, USDA Forest Service, Southern Research Station,

Pineville, LA.
Contents

 Page

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Selecting Seedlots . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Collecting and Processing Cones . . . . . . . . . . . . . . 5

Collecting Cones . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Handling Cones . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Processing and Handling Seeds . . . . . . . . . . . . . . . 12

Drying Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Dewinging and Cleaning Seeds . . . . . . . . . . . . . . 12

Storing and Testing Seeds . . . . . . . . . . . . . . . . . . . 13

Treating Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Sowing Seeds and Caring for Seedlings . . . . . . . . 15

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
ii

Preface

The guidelines that follow represent current knowledge and research studies

on how to collect, process, treat, and store longleaf pine seeds for nursery use.

Experience has shown that results from small research studies may be difficult

to apply on an operational scale because longleaf pine seeds are unusually

sensitive to injury. However, these guidelines provide the best information

available on handling cones and seeds of this species. Seed dealers and orchard

and nursery managers will need to adapt these principles and procedures to

their own operations.
1

Guidelines for Producing

Quality Longleaf Pine Seeds

James P. Barnett and John M. McGilvray

Abstract

Longleaf pine (Pinus palustris Mill.) seeds are sensitive to damage during collection,

processing, treatment, and storage. High-quality seeds are essential for successfully producing

nursery crops that meet management goals and perform well in the field. Uniformity in the

production of pine seedlings primarily depends on prompt and uniform seed germination, early

seedling establishment, and a variety of cultural practices that are applied as the seedlings

develop. The best collecting, handling, and processing methods maximize performance

attributes and reduce the need for extensive nursery cultural practices to compensate for poor

seed quality. Guidelines are presented that will help seed dealers, orchard managers, and nursery

personnel produce high-quality longleaf pine seeds and improve the efficiency of nursery

production.

Keywords: Container and bareroot nursery production, Pinus palustris, seed germination, seed

orchard management, seed physiology, seed quality.

Introduction

Interest in restoring longleaf pine (Pinus palustris Mill.) to many sites in the

South has increased dramatically over the last decade (fig. 1). One of the

limitations in producing the quantities of seedlings needed for this reforestation

effort is the lack of sufficient quantities of high-quality seeds. Although the

quantity of seeds collected and seedlings produced has increased markedly, the

quantity and quality of longleaf pine seeds remain insufficient to meet demand

across the range of the species. Producing consistently high-quality seedlings

requires prompt and uniform seed germination and early seedling establishment

(fig. 2). Most nursery managers should be able to maintain 85-percent or higher

germination and 90-percent or higher survival after the emergence of seedlings.

Otherwise, oversowing will be necessary, and the subsequent waste of seeds

will jeopardize efforts to produce high-quality crops economically and

consistently.

With seeds of loblolly (P. taeda L.) and slash (P. elliottii Engelm.) pines

relatively easy to collect, process, and maintain, why are nursery managers

unable to produce similar quantities of quality longleaf pine seeds? The

answers to this question can be found by examining the uniqueness of the

species.
2

Figure 1—A recently regenerated longleaf pine stand showing vigorous early growth.

Figure 2—Prompt and uniform seed germination is the key to efficient production of container

longleaf pine seedlings.
3

First, seed production of longleaf pine is extremely variable from year to year

and from place to place. Although some open-grown trees will bear cones

every year, crops are usually sporadic. A 21-year period in south Mississippi

produced seed crops that were heavy for 2 years, medium for 7 years, light for

5 years, and failures for 7 years (Maki 1952). Boyer (1987) observed that the

frequency of acceptable crops ranged from zero for a 19-year period to three

for a 4-year period. The frequency of good crops appeared to be lower near the

Gulf Coast than farther inland. Poor cone crops can result from lack of

flowering or from insect damage to cones, particularly when crops are light

(Allen and Coyne 1956, Barnett and Haugen 1995). Review of the physiology

of cone and seed production indicates that reducing numbers of trees per acre is

the most effective method of improving seed productivity (Barnett and Haugen

1995).

Second, the relationship between cone and seed maturity in longleaf is unique

among the southern pine species. Longleaf seeds do not mature (germinate

well) until the cones are mature enough to be opened operationally (Barnett

1996a). Therefore, to ensure that seeds have high viability, you must delay cone

collection until the seeds are fully mature.

Third, unlike slash and loblolly pine, longleaf pine has an extremely short

period of seed dormancy, often germinating immediately after separating from

the cones. Therefore, proper handling before storage is critical. Because

longleaf seeds are large and fragile with permanently attached wings, have thin,

easily cracked seedcoats, and are unusually moist when extracted from cones,

they are the most difficult of the southern pines to successfully collect, process,

store, and treat without adversely affecting quality (fig. 3) (Barnett and

Pesacreta 1993, Wakeley 1954).

Results from recent tests, combined with other documented findings and

recommendations that will help you produce high-quality longleaf pine seeds,

are reported in this paper.

Selecting Seedlots

About 450 acres of first-generation longleaf pine seed orchards have been

established in the South (Dennington and Farrar 1983), with the primary

emphasis of breeding for fast initial height growth and resistance to brown-spot

needle blight (Mycosphaerella dearnessii Barr). Because these orchards can
4

only supply limited quantities of genetically improved longleaf pine seeds,

reforestation must depend on collections from healthy, vigorous stands.

Although the most conservative approach is to select seedlots from local

sources, using nonlocal seed involves minimal risk if you follow the guidelines

below.

Geographic variations in longleaf pine, although not as obvious as in loblolly

and slash pine, are important to commercial growers (Lantz and Kraus 1987).

For example, seedlings from central Florida sources have poor survival when

planted north of peninsular Florida. Schmidtling (1999) found no ecotypic

differentiation in the species—with few genetic differences between stands

from deep sand sites and stands from heavier soils—and no important

differences between eastern and western sources. The natural range of longleaf

pine (fig. 4) consists of five primary collection or planting isotherms or both

(formerly called zones) based on average minimum temperature (Schmidtling

2001). Seed can thrive if planted in an isotherm from which it was collected.

Growth will be hastened by planting seed from one isotherm warmer and

slowed by planting from one isotherm colder. Seed should not be moved more

Figure 3—Reasons for longleaf pine seed vulnerability to damage—large size, thin seedcoats,

and wings that must be reduced to stubs.
5

Figure 4—Longleaf distribution with seed transfer guidelines (Schmidtling 2001).

than one isotherm. Certification of seed sources by crop improvement

associations in all Southern States provides valuable third-party verification of

seed source.

Collecting and Processing Cones

The ability to predict cone and seed yields is important in scheduling and

allocating resources for cone collection. Barnett (1999) published guidelines

for predicting the number of cones per tree and converting to bushels,

estimating numbers of seeds per cone, and converting numbers of seeds per

bushel to pounds of seed per bushel. Once these data are available, scaling up

of information for crop prediction is straightforward.

Collecting Cones

Careful control of cone collection is the first step in producing high-quality

longleaf pine seeds (fig. 5). The most common source of early losses in seed

quality is from cones collected before the seeds are fully mature. The

25 25 Minimum temperature isotherms (∞F)

Natural distribution of longleaf pine

Seed transfer guidelines

TX

OK

MO

AR

LA MS

TN

AL

FL

GA

SC

NC

VA

WV

PA

MD

25

25

20

20

20

20

15

15

10

10

5

5

0

0

KY

IL

IN

OH DE

NJ

-5

-5

-10

-10

30 30

35
6

Figure 5—Collecting longleaf pine cones in a seed orchard with a cone shaker.
7

recommended timing of southern pine cone collections has not changed since

Wakeley (1954) showed that a cone is mature enough for seed extraction when

its specific gravity drops below 0.89. Two factors make specific gravity the best

predictor of seed maturity: first, that water content decreases as cones mature;

and second, that cone-specific gravity (the weight of freshly picked cones

divided by their volume) is an indirect measure of moisture content. A

graduated cylinder technique is a simple alternative for determining conespecific gravity (Barnett 1979a). Fill a cylinder to a convenient level and record

that level. Carefully place the cone in the cylinder and, if floating, record the

new level (if the cone sinks, the specific gravity is 1.0 or more). The difference

between the two recorded levels is cone weight. With a wire or small object,

submerge the cone and record the third water level; the difference between this

third level and the initial level is cone volume. Because longleaf cones are

often too large to fit a standard-sized, graduated cylinder, Karrfalt (in press)

devised a second alternative that uses a 3-inch PVC pipe (fig. 6). A third,

nearly foolproof alternative is to float cones in oil that has a specific gravity of

0.88. There is little room for error in the oil flotation technique, but newer oil

formulations make finding an appropriate specific gravity oil difficult.

Recent data confirm that collection should be delayed until cones are fully

mature (fig. 7) because viability of longleaf seed from immature cones may

decrease during cone storage if seeds have not reached some undetermined

stage of ripeness (Barnett and Pesacreta 1993).

Additional tests were conducted to determine potential sources of major seedquality losses. During two collection periods, specific gravity was measured for

cones harvested from several clones in the Stuart Seed Orchard at Pollock, LA.

Average specific gravity (table 1) was 0.86 for collection 1 (October 5 to 6)

and 0.81 for collection 2 (October 20). Even with an average of 0.86, specific

gravity was much higher for many individuals in collection 1, supporting

Wakeley’s (1954) recommendation that cone collection not begin until specific

gravity for 19 of 20 cones is <0.89. If the data in table 1 are representative of

all longleaf pines, average specific gravity must be about 0.81 before

Wakeley’s criteria are met.

The Louisiana data also support the previous conclusions that seed yields

increase as specific gravity decreases (fig. 8). Seed germination was also

markedly affected by cone maturity, with collection 1 germination averaging 49

percent compared to 69 percent for collection 2.
8

Figure 6—A method for

quickly determining

specific gravity of

longleaf cones (Karrfalt,

in press) involving a 3-

inch PVC pipe plugged at

one end: (A) install a 1/4-

to 1/2-inch drain near the

top of the PVC pipe and

pour water into the PVC

pipe until it begins to flow

through the drain; (B) to

determine cone weight,

place a 100-mL graduated

cylinder beneath the

drain, place the cone in

the PVC pipe, and record

the amount of water that

flows into the graduated

cylinder; (C) to determine

cone volume, submerge

the cone and record the

amount of additional

water that flows into the

graduated cylinder.

A

C

B
9

Figure 7—Fully mature longleaf pine cones.

Table 1—Longleaf pine cone-specific gravity, seed yields, and

germination for two collection periods (October 5 to 6 and October 20)

Cone-specific gravitya

Collection Seed

period Average Above 0.89 Above 0.87 yields Germination

 - - - - - - Percent - - - - - - Lbs/bu Percent

1 0.86 27 44 0.49 49

2 .81 4 7 .73 69

a Specific gravity values represent an average of 20 replications of 10 cones each per

collection period.
10

Handling Cones

The effectiveness of ripening immature cones to improve viability versus

holding them before seed extraction is unclear (Barnett 1996b, Bonner 1987,

McLemore 1975), but some cone storage is needed to improve seed yields.

However, McLemore (1961) showed that delaying cone extraction beyond

about 4 weeks may jeopardize seed quality (fig. 9).

How cones are stored is important. If cones are properly aerated and kept dry,

you may store them in burlap bags, 20-bushel crates (fig. 10), or on drying

racks. Exposure to rain can cause premature sprouting of the seeds in opening

cones and significant reduction in quality. If cones remain wet, pathogenic

fungi can develop, reducing seed viability and vigor and increasing mortality of

newly germinated seedlings (Barnett and others 1999).

Drying normally takes place in a kiln (pressurized drier) where heated air is

forced through the cones to reduce relative humidity. Drying duration depends

on the moisture content of the cones when placed into the kiln and on the

Figure 8—Seed yields and germination (shown above bars) of longleaf pine as affected by

date of collection and cone storage (Barnett 1979a). When case hardened, seeds were

removed artificially.

Stored 1 week

Stored 3 weeks

Stored 5 weeks

100

80

60

40

20

0

 Seeds per cone (released naturally)

Specific gravity (top row) and date (bottom row)

0.98 0.93 0.89 0.85 0.80

9/15 9/22 9/29 10/6 10/13

64

31

20

71

43

43

73

74

60

81

74

60

91

90

91
11

Figure 10—Storing longleaf pine cones in 20-bushel wooden crates prior to seed extraction.

Figure 9—Effect of delayed cone extraction on longleaf seed germination initially

and after 1 year of seed storage (McLemore 1961).

Initial

After 1 year of storage

Germination (percent)

100

80

60

40

20

0

Days to extraction

0 15 30 60 90
12

outside temperature and humidity. Avoid drying on warm, rainy days. Cones

dry in 24 to 48 hours at 30-percent relative humidity (Karrfalt, in press), but

they stop drying at 50 percent. Be sure to use the lowest temperature feasible to

reach the desired level of relative humidity. Never allow kiln temperatures to

get higher than about 115 ∞F.

When the cones are dry enough to open and release their seeds, the next step is

to place them in a tumbler, which usually contains a perforated cylinder that

allows the seed to separate from the cones and fall through the holes. Promptly

remove the seeds from the tumbler to avoid damage to the seedcoats.

Processing and Handling Seeds

Drying Seeds

Extracted longleaf seeds have unusually high moisture contents requiring

immediate refrigeration to avoid deterioration, closely followed by drying to 8-

to 10-percent moisture content (see instructions for cone drying). A separate

seed drier is a necessary investment only if you are processing large quantities

of longleaf seeds. Either way, do not discontinue drying until you have run

moisture tests to ensure that the seed moisture content is at a safe level for

storage. Seeds may then be sealed in moisture-proof containers, but they should

be stored at a maximum of 35 ∞F if dewinging and final cleaning will not take

place within 2 weeks (Karrfalt, in press).

Dewinging and Cleaning Seeds

Seed dewinging requires great care and appropriate equipment to reduce wings

to stubs rather than completely removing them. Improper dewinging is a

common source of quality problems in longleaf seeds and was shown to reduce

germination by 13 percent (Barnett 1996a). Earlier studies showed that

germination can be kept at a high level if longleaf seeds are dewinged carefully

(Barnett 1969, Belcher and King 1968). Other sources of reduced seed quality

are inadequate seed drying and damage during processing of the large-sized

seeds.

A combination of screening and air separation is an effective method for

removing detached wings, cone scales, and other trash. The next step is to

remove empty and partially filled seeds on a gravity table (a shaking, inclined

table with air blowing through it from the bottom). An intermediate step for
13

some seed processors is to size the seeds for more efficient separation and

increased uniformity of germination. However, Dunlap and Barnett (1983)

showed that this intermediate step does not significantly improve total

germination.

The cleaning process upgrades seed quality, but it cannot correct for poor

handling at earlier stages. Every stage in seed handling from estimating cone

maturity to operation of the gravity table must be done correctly to have the

high-quality seeds needed for nursery operations.

Storing and Testing Seeds

To maintain quality, store the dried and cleaned seeds in moisture-proof

containers such as cardboard drums or waxed boxes with foil or polyethylene

liners (4- to 6-mils thick). Tightly sealing the containers keeps moisture content

at the required 8 to 10 percent. You may store seeds for 3 years or less if you

keep temperatures near freezing (35 ∞F). For longer periods, lower temperatures

to subfreezing, preferably between 0 and 20 ∞F. Barnett and Jones (1993)

showed that longleaf seeds can retain their viability for 20 years when held at

0 ∞F (fig. 11).

Before packaging and storing seeds, weigh them and run germination and

purity tests to facilitate pricing and estimating the correct amount for sowing.

Conduct follow-up germination and moisture content tests every 2 years, 2 to 3

months before sowing, immediately before selling seeds, and immediately after

delivery of purchased seeds to check for damage during storage and transport.

The germination tests are especially important in guarding against crop failure

because they reduce the risk of sowing poor viability seeds.

Treating Seeds

Although early researchers suggested that some seedlots might benefit from

short periods of prechilling or stratification (U.S. Department of Agriculture,

Forest Service 1948; Wakeley 1954), they also cautioned that longleaf pine

seeds frequently begin to germinate during stratification. As knowledge about

proper collecting, processing, and storing of longleaf seeds increased, most

researchers and practitioners concluded that stratification is unnecessary. In

recent years, however, interest in stratification of longleaf seeds has

reemerged—resulting from the desire to upgrade or improve performance of

poor-quality lots. Karrfalt (1988) reported that stratification for 14 days

(imbibed on media in germination dishes) improved both speed and total
14

Figure 11—Germination of longleaf pine seeds as influenced by moisture content and

years of storage at (A) 0 ∞F and (B) 34 ∞F (Barnett and Pesacreta 1993).

A

B

100

75

50

25

0

0 4 8 12 16 20

 Years

6 9 12

15 18

Moisture content (percent)

Germination (percent)

100

75

50

25

0

0 4 8 12 16 20

 Years

6 9 12

15 18

Moisture content (percent)

Germination (percent)
15

germination in almost all the 54 seedlots tested, most of which had relatively

low viability. Others showed that stratification (imbibed by soaking overnight

in water) hastened germination about 2 days but also reduced total germination

by about 10 percent (Barnett and Jones 1993). The disparity in these results

may relate to the method of moisture imbibition and reinforces the advice that

adoption of this procedure be made with caution. A preliminary small trial will

help you to learn the technique and to be sure it works in your seedlots.

Longleaf pine seedcoats are hosts to significant populations of pathogenic fungi

(Barnett and Pesacreta 1993, Pawuk 1978). Germination of less vigorous seeds

may be improved by treating them with a sterilant, such as hydrogen peroxide

(Barnett 1976), or by applying a drench of a fungicide such as benomyl (fig.

12). A 30-percent hydrogen peroxide soak for an hour improves seedling

establishment by as much as 14 percent (table 2), but it requires careful

handling because it is a strong oxidant that can cause skin and eye injuries.

Tests show that 10-minute drenches of seed in a fungicide solution such as

benomyl are equally effective (table 3), safer, and less expensive.

Sowing Seeds and Caring for Seedlings

Whether done in a bare-root or container nursery, the ideal timing of sowing

depends on environmental conditions. Longleaf pine seeds require appropriate

temperature, moisture, and light conditions to germinate promptly. If moisture

conditions are adequate, longleaf seeds have little dormancy and normally

germinate in the fall—soon after release from the cones. Therefore, the

optimum temperature for longleaf germination (about 68 ∞F) is cooler than it is

for the other southern pines (Barnett 1979b). For this reason, springtime sowing

should take place in late April or May while temperatures are still low (fig. 13).

Because longleaf seeds have little dormancy, they are not greatly sensitive to

light levels. Some covering (about one-fourth inch) helps to maintain good

moisture conditions for germination (fig. 14), but deep covering of seeds will

inhibit germination because longleaf hypocotyls are too short to push the

seedlings to the surface. Seeds that are deeply covered and kept moist for an

extended period are also likely to succumb to pathogenic fungi (Barnett 1978).

Uniform moisture conditions are needed to obtain uniform germination and

seedling development. Proper irrigation requires considerable skill to maintain

desired moisture levels. Lack of appropriate moisture control frequently causes
16

Figure 12—Longleaf pine seeds without (A) and with (B) an application of a sterilant to

reduce pathogenic fungi on the seedcoat. (Photos courtesy John P. Jones, Louisiana State

University, Baton Rouge, LA.)
17

Table 2—Longleaf pine seedling percentages from seed and seedling treatments

Seed treatmenta

Seedling treatment Control Hydrogen peroxide Average

 - - - - - - - - - - - Percent - - - - - - - - - - -

Control 78 92 85a

Benlate® 85 93 89b

Fungo-flo® 88 94 91b

Fungo-flo®

 plus Subdue® 90 94 92b

Average 85a 93b

a Seedling percentages (numbers plantable in November divided by numbers with an initial germinant) are averages for 288 seedling cavities for each of 3 replications. Averages within columns

and across rows followed by the same letter are not significantly different at the 0.05 level.

Source: Barnett and McGilvray (2002).

Table 3—Germination of longleaf pine seed and seedling stocking following

treatments in 1997 under laboratory and nursery conditionsa

Germination Stockingc

Treatments Peak dayb STF NTSL CN1 CN2 CN1 CN2

 No. - - - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - -

Control 7.0ab 76b 71c 75bc 72c 66bc 64b

Hydrogen peroxide 7.2a 84a 84a 70d 81ab 70b 78a

HP + 16-hr water

 soak 6.0bc 71b 74c 84a 85a 81a 80a

HP + WS + 14-day

 strat. 4.4d 76b 78b 79abc 85a 77a 82a

WS + 14-day strat. 4.0d 85a 84a 79bc 77bc 54d 50c

Mist + 14-day strat. 5.0c 86a 82ab 80ab 76bc 62c 65b

HP = hydrogen peroxide; WS = water soak.

a Germination 28 days after sowing in the Pineville Laboratory (STF), the Dry Branch Laboratory

(NTSL), and the Claridge Nursery (CN1 and CN2 are two separate tests of the same treatment

applications sown 2 weeks apart). Averages within columns followed by the same letter are not

significantly different at the 0.05 level.

b Peak day is the time when maximum daily germination occurs and is a measurement of

germination speed.

c Seedling stocking is the percentage of seeds that became viable seedlings 90 days after sowing.

Source: Barnett and others (1999).
18

Figure 14—A crop of longleaf pines seeded and grown in containers under uniform moisture

conditions.

Figure 13—Sowing longleaf pine seeds in containers—typically in late April.
19

poor germination and problems in early seedling development. Too much

moisture may cause preemergence damping off, and too little may delay

germination and cause erratic development.

Conclusions

High-quality seeds are essential for the uniform production of high-quality pine

seedlings either in containers or in bare-root nurseries. Steps that are critical for

obtaining quality longleaf pine seeds include: delaying collections until cones

are fully mature, processing properly stored cones within 4 to 6 weeks after

collection, promptly drying extracted seeds to moisture contents of 10 percent

or less, dewinging seeds very carefully to avoid coat damage, cleaning seeds to

remove trash and empty or partially filled seeds, storing at low temperatures,

and treating before sowing to remove seedcoat pathogens. Adapting these

principles and procedures to your operations will improve seed viability and

lower overall costs.

Literature Cited

Allen, R.M.; Coyne, J.F. 1956. Insect problems in forest-tree genetics. Journal of Forestry.

54: 193.

Barnett, J.P. 1969. Long-term storage of longleaf pine seeds. Tree Planters’ Notes. 20(2):

22–25.

Barnett, J.P. 1976. Sterilizing southern pine seeds with hydrogen peroxide. Tree Planters’

Notes. 27(3): 17–19, 24.

Barnett, J.P. 1978. Covering affects container germination of southern pine seeds. Tree

Planters’ Notes. 29: 13–15.

Barnett, J.P. 1979a. An easy way to measure cone specific gravity. In: Proceedings of a seed

collection workshop. Tech. Publ. SA–TP 8. Atlanta: U.S. Department of Agriculture, Forest

Service, State and Private Forestry: 21–23.

Barnett, J.P. 1979b. Germination temperatures for container culture of southern pines. Southern

Journal of Applied Forestry. 3: 13–14.

Barnett, J.P. 1996a. How seed orchard culture affects seed quality: experience with the

southern pines. Forestry Chronicle. 72: 469–473.
20

Barnett, J.P. 1996b. Longleaf pine seed quality: can it be improved? In: Landis, T.D.; South,

D.B., coords. Proceedings: forest and nursery conservation nursery association. Gen. Tech. Rep.

PNW–389. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest

Research Station: 69–74.

Barnett, J.P. 1999. Guidelines for estimating cone and seed yields of southern pines. In:

Proceedings of the 25th biennial southern forest tree improvement conference. Sponsored Publ.

47. Baton Rouge, LA: Southern Forest Tree Improvement Committee: 31–35.

Barnett, J.P.; Jones, J.P. 1993. Response of longleaf pine seeds to storage conditions and

pregermination treatments. Southern Journal of Applied Forestry. 17: 174–179.

Barnett, J.P.; McGilvray, J.M. 2002. Improving longleaf pine seedling production by

controlling seed and seedling pathogens. In: Outcalt, Kenneth W., ed. Proceedings of the

eleventh biennial southern silvicultural research conference. Gen. Tech. Rep. SRS–48.

Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station:

45–46.

Barnett, J.P.; Pesacreta, T.C. 1993. Handling longleaf pine seeds for optimal nursery

performance. Southern Journal of Applied Forestry. 17: 180–187.

Barnett, J.P.; Pickens, B.; Karrfalt, R. 1999. Improving longleaf seedling establishment in the

nursery by reducing seedcoat microorganisms. In: Haywood, James D., ed. Proceedings of the

tenth biennial southern silvicultural research conference. Gen. Tech. Rep. SRS–30. Asheville,

NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 339–343.

Barnett, James P.; Haugen, Ronald O. 1995. Producing seed crops to naturally regenerate

southern pines. Res. Pap. SO–286. New Orleans: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station. 10 p.

Belcher, E.W., Jr.; King, J. 1968. Storage of dewinged longleaf pine seed is possible. Georgia

For. Res. Counc. Res. Pap. 51. Macon, GA: Georgia Forestry Commission. 4 p.

Bonner, F.T. 1987. Cone storage and seed quality in longleaf pine. Res. Note SO–341. New

Orleans: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station.

4 p.

Boyer, W.D. 1987. Annual and geographic variations in cone production by longleaf pine. In:

Phillips, Douglas R., comp. Proceedings of the fourth biennial southern silvicultural research

conference. Gen. Tech. Rep. SE–41. Asheville, NC: U.S. Department of Agriculture, Forest

Service, Southeastern Forest Experiment Station: 73–76.

Dennington, Roger W.; Farrar, Robert M., Jr. 1983. Longleaf pine management. For. Rep.

R–8–FR 3. Atlanta: U.S. Department of Agriculture, Forest Service, Southern Region. 17 p.

Dunlap, J.R.; Barnett, J.P. 1983. Influence of seed size on germination and early development of

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654. Washington, DC: U.S. Department of Agriculture, Forest Service. 416 p.

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22
Barnett, James P.; McGilvray, John M. 2002. Guidelines for producing quality

longleaf pine seeds. Gen. Tech. Rep. SRS–52. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southern Research Station. 21 p.

Longleaf pine (Pinus palustris Mill.) seeds are sensitive to damage during collection,

processing, treatment, and storage. High-quality seeds are essential for successfully

producing nursery crops that meet management goals and perform well in the field.

Uniformity in the production of pine seedlings primarily depends on prompt and

uniform seed germination, early seedling establishment, and a variety of cultural

practices that are applied as the seedlings develop. The best collecting, handling, and

processing methods maximize performance attributes and reduce the need for

extensive nursery cultural practices to compensate for poor seed quality. Guidelines

are presented that will help seed dealers, orchard managers, and nursery personnel

produce high-quality longleaf pine seeds and improve the efficiency of nursery

production.

Keywords: Container and bareroot nursery production, Pinus palustris, seed

germination, seed orchard management, seed physiology, seed quality.
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