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EXPORTING
LEATHERLEAF FERN
TO EUROPE

IN VAN CONTAINERS

(gms, UNITED STATES MARKETING PREPARED BY
3 :) DEPARTMENT OF RESEARCH SCIENCE AND
S&B AGRICULTURE REPORT EDUCATION

NUMBER 1103 ADMINISTRATION

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Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

ABSTRACT

Miller, W. R., L. A. Risse, T. Moffitt, and A. J. Bongers. 1979.
Exporting leatherleaf fern to Europe in van containers. U.S. Department of
Agriculture, Marketing Research Report No. 1103, 18 pp.

This report details stowage and shipping procedures for exporting leather-
leaf fern (Rumohra adiantiformis (G. Forst.) Ching) in van containers. Guide-
lines are recommended that will improve the arrival condition of fern in export
markets. These recommendations were developed by studying product temperature
profiles of 11 test loads in relation to thermostat settings of refrigeration
units and loading patterns used to stow boxes in van containers.

Recommended product temperatures for storing and shipping leatherleaf
fern are 34°-40° F (1.19-4.4° C). When shipped in commercial van containers,
it must be stowed in loading patterns that provide air channels through the
load mass. Air channels allow free circulation of refrigerated air from the
source of discharge to the return side of the refrigeration system. Discharge
air temperature will fluctuate from the thermostat setting, especially during
the first few days after loading. This is especially true when ferns are not
precooled to recommended storage temperatures prior to loading in van con-
tainers. Thermostats must be properly calibrated to manufacturers’ specifi-
cations prior to loading and set at 37° + 1° F (2.8° ¢ 0.69 Cc).

KEYWORDS: Leatherleaf fern, export, van container, shipping, quality,
stowage patterns.

For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402

Stock Number 001-000-03966-1

ACKNOWLEDGMENTS

The following companies and organizations assisted in this research:
Florida Leatherleaf and Plumosus Growers, Inc., Pierson, Fla.; Uniflora
Florida, Yalaha, Fla.; Volusia Fern Co., Pierson, Fla.; Uniflora Europe,
Hamburg, Germany; S. Zurel & Co., B.V., Aalsmeer, the Netherlands; Sea-—Land
Services, Inc., Elizabeth, N.J.; and U.S. Lines, New York, N.Y.

Science and Education Administration personnel who collected data at
points of origin, destination, or both during this study included Roy McDonald
and Ben Hillebrand, European Marketing Research Center, Rotterdam, the
Netherlands, and Francis Marousky, Bradenton, and Randall Cubbedge, Orlando,
Fla. Victor Chew (SEA), Gainesville, Fla., provided the computer science
expertise for handling and plotting the temperature data for this project.

The research was conducted under the general leadership of T. T. Hatton, SEA
research leader, Orlando.

Lii

CONTENTS

Page
Materials and methods—-----------------------------—---------------------- 2
Results-------------—-- -- —--- ---- - —-- -- --- ~~ - - +--+ 9
Conclusions---------——--- ---- -- - --- - -- -- = -- - --- -- - -- --- -- —- + -- 14
Appendix-------~------------------------ ----- --------- -- -- ——-- ----------- 16

Washington, D.C. Issued April 1979

EXPORTING LEATHERLEAF FERN TO EUROPE IN VAN CONTAINERS

By W. R. Miller, 1/ L. A. Risse, 2/ T. Moffitt, 2/ and A. J. Bongers 1/

Leatherleaf fern (Rumohra adiantiformis (G. Forst.) Ching) is an important
commercial horticultural commodity produced in central Florida. Total fern
acreage in Florida for 1977 was estimated at 2,500. Approximately one-half of
this acreage was in leatherleaf fern. During the 1977-78 reporting period,
approximately 23 percent of the total fern shipments were exported; 3/

45 percent of this volume was shipped by surface transport (ships) in van con-
tainers and the remainder by air. Leatherleaf ferns were exported primarily
to the Netherlands and West Germany, where importers distributed the product
to destinations throughout western Europe.

Several years ago, major U.S. shipping companies indicated that claims
against their companies for fern were excessive. The major reported problems
were either heating or freezing damage to the fern during transit that made the
product unsalable. Some shippers and receivers indicated that they would stop
exporting or importing fern if better product quality could not be maintained.

The recommended storage and shipping temperature for leatherleaf fern is
349-409 F (1.19-4.4° C), with 90-95 percent relative humidity. 4/ If ferns
are maintained at these environmental conditions, they can be stored or trans-
ported to export markets and arrive with sufficient shelf life for successful
marketing.

The purpose of this report is to provide growers, packer-shippers,
carriers, and receivers of leatherleaf fern with recommended handling, stowage,
and shipping procedures that will achieve the best possible arrival condition
with minimum losses from damage during transit. To attain this purpose,
several shipments of leatherleaf fern were monitored during transit to deter-
mine product temperatures relative to temperatures of refrigerated air,
uniformity of temperatures relative to stacking patterns, and product condition
on arrival.

1/ Agricultural marketing specialist and agricultural research specialist,
respectively, European Marketing Research Center, Science and Education
Administration, U.S. Department of Agriculture, Rotterdam, the Netherlands.

2/ Agricultural marketing specialist and industrial engineering technician,
respectively, U.S. Horticultural Research Laboratory, Science and Education
Administration, U.S. Department of Agriculture, Orlando, Fla. 32803.

3/ Florida Department of Agriculture and Consumer Services. Fresh flowers
and ferns - summary 1977-78. 33 pp. Winter Park, Fla. 1978.

4/ Lutz, T. M., and Hardenburg, R. E. The commercial storage of fruit,
vegetables and florist and nursery stocks. U.S. Dept. Agr. Agr. Handb. 66,

94 pp. 1977.

MATERIALS AND METHODS

During 1975-76, 11 refrigerated van containers of leatherleaf fern were
evaluated and temperatures monitored en route from Florida to Europe (table 1).

Ferns were harvested from shaded ferneries, sized according to frond
length, and tied together in bunches containing 25 fronds each. The bunches
were transported to the packinghouse, dipped in a fungicide or moistened with
water, and placed in polyethylene liners inside moisture-resistant, corrugated
fiberboard boxes. Perforated polyethylene liners were used to completely
encase the ferns inside the boxes. Twenty to forty-five bunches of fern were
packed per box depending on the fern and box size. Boxes were closed with
staples.

Ferns were packed in four box sizes. The outside dimensions (length by
width by depth) were as follows:

In (Cm)

30 x 21% AY (76.2 =, 53.53 x 27.9)
30) x 21x 6: (7662.x 553.3%. 15,52)
27 x 15 x 15 (68.6 x 38.1,x: 3821)
30x 14x. 9 (76.2 x. 35.6 x*22.9))

All boxes were regular slotted containers constructed of single-wall, corru-
gated fiberboard. They were either wax coated or wax impregnated with a
bursting strength of at least 275 pounds (124.7 kg) (Mullen test). After
packing, boxes were placed in either refrigerated storage or unrefrigerated
holding areas until they were loaded into the van container.

Specific stowage patterns used to stack boxes in the van containers
depended on box size. The stowage patterns for box sizes tested were as
follows:

Stowage pattern Box size
In (Cm)
5 x 3 modified bonded block----- 27x 15x 1S. (68.6 = 38.0 738.2)
Parallel air channels----------- 30 20 ox a 'C76%.2" X& 53.50 27.9)

30 sx"2'T) x 96 C7652 «x, 53.07%. 1522)
30°x 14 x19" (76.2) |x. 35.6" 22.9)

1 load tight stacked------------ 30°x 21 sx C72. 3.x 209)

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Cargo air and product temperatures were recorded at l-hour intervals from
time of loading at shipping point until unloading at destination. All temper-
ature measurements were recorded using automatic temperature instruments with
thermistor-type sensing probes. Twenty-four temperature probes were used in
each van container. Eighteen probes monitored temperature at sélected loca-
tions and 6 probes monitored ceiling, floor, discharge, and return air temper-
ature in the van container (fig. 1). All product temperature probes were

A B c AIR DUCT

AIR PLENUM

REEFER

RETURN AIR

TOP LAYER

3D LAYER

1ST LAYER

SENSOR LOCATIONS
® AIR TEMPERATURE

@FERN TEMPERATURE

Figure 1.--Location of 6 cargo area air and 18 product temperature sensors
in a typical test van container, showing end view through load.

placed in the center of a designated box in the center of a fern bunch. Tem-
peratures were individually sensed and recorded by each probe and the data were
processed and plotted by a computer.

Test shipments 1 and 2, consisting of four van containers, are selected
for detailed discussion with temperature results depicted graphically. Major
highlights are presented for test shipments 3-7. Test shipments 1-4 each
consisted of van containers A and B, which were loaded by a single shipper and
transported on the same voyage. Thus, both van containers A and B in each of
the test shipments 1-4 were subjected to similar handling and environmental
factors. The van containers in each particular test had similar refrigeration,
insulation, and dimensional characteristics. The ferns in each van container
were from several growers, but sample boxes used for observations were from

the same lot. Data collected in these shipments included the product tempera-
tures relative to thermostat settings and loading patterns and the box and
product condition on arrival.

In test shipment 1, boxes 30 x 21 x 11 and 30 x 21 x 6 inches
(76.2 x 53.3 x 27.9 and 76.2 x 53.3 x 15.2 cm) were loaded in each van con-
tainer. The 1l-inch (27.9-cm) deep boxes were placed in the header stack
(fig. 2) and the lower three layers of all remaining stacks (fig. 3). The

Figure 2.--End view of header stack (lst stack), with boxes 30 x 21 x jl
inches (76.2 x 53.3 x 27.9 cm) placed in van container.

mOR.

LAYER 3-4}

Figure 3.--Rear view of parallel air channel loading pattern used for
boxes 30 x 21 x11 and 30 x.21 x 6 inches (76.2 x 53.3 x 27.9

and 76:2 x 53.3 x 15.2 cm) in layers 3 and 6, 7.

Air channels
are shaded.

boxes were stowed so that nonrestricted parallel air channels were maintained
the entire length of the load. In test shipment 2, van A, boxes 27 x 15 x 15
inches (68.6 x 38.1 x 38.1 cm) were stacked in a modified bonded-block pattern
(fig. 4). In van container B of test 2, boxes 30 x 14 x 9 inches (76.2 x

35.6 x 22.9 cm) were stowed with parallel airflow channels in layers 3 and 6
(fig. 5)-

Van containers used in test 1 measured 454 inches (11.53 m) long by 87
inches (2.21 m) wide and 86 inches (2.18 m) high (ID - internal dimensions).
Refrigerated air was discharged through finger ducts at the ceiling and

Sheet |

Figure 5.--Rear view of parallel air channel loading pattern used for
boxes 30 x 14 x 9 inches (76.2 x 35.6 x 22.9 cm). Air channels
in layers 3 and 6 are shaded.

returned to the refrigeration unit at the bottom of the forward bulkhead. Van
containers used in test 2 measured 386 inches (9.80 m) long by 88 inches

(2.23 m) wide and 87 inches (2.21 m) high (ID). Refrigerated air was dis-
charged through a single duct extending approximately two-thirds the length of
the van and returned to the refrigeration unit through 2-inch (5.l-cm) diameter
holes in the lower half of the forward bulkhead and through an opening just
forward of the "T" rails at the bottom of the forward bulkhead.

All shipments were destined for either the Netherlands or West Germany.
Transit time varied from 10 to 23 days. The van containers were loaded at a
cooperating shipper's warehouse in central Florida and trucked to the port of

Jacksonville, Fla. Van containers destined for the Netherlands were unloaded
at the port of Rotterdam and trucked to the receiver's warehouse. Van con-
tainers destined for West Germany were discharged at either the port of
Rotterdam, the Netherlands, or the port of Bremen, West Germany, and then
trucked to the receiver's warehouse in Hamburg, West Germany.

Test shipments were loaded under the supervision of USDA researchers, who
determined stowage patterns and thermostat settings and installed temperature
monitoring instruments in the van containers. At destination, USDA researchers
recovered the instruments and observed the condition of the ferns and the
stability of boxes in the stowage pattern.

RESULTS

Temperatures recorded during all test loads include mean product tempera-
tures at 24-hour intervals relative to the thermostat settings and loading
patterns and the range of discharge air temperatures between 24 and 96 hours of
transit time (table 1).

In test 1, thermostats on van containers A and B were set at 38° F
(3.3° C). Mean fern, discharge, and return air temperatures for van containers
A and B of test 1 are shown in figure 6. The automatic recorder monitoring
temperatures in van container A malfunctioned after 148 hours. Initial mean
fern temperature at loading in van A was approximately 60° (15.6°) compared
with 45° (7.2°) in van container B. It stabilized near discharge air tempera-
ture in about 60 and 28 hours after loading in van containers A and B, respec-
tively. Temperature of discharge air delivered by the refrigeration units in
both van containers generally fluctuated between 30° and 38° Ci and 3.3°).
There was a greater difference between the extreme high and low product tem-
peratures during the time product temperatures were decreasing in van container
A as compared with van container B. This occurred because van container A had
several lots of ferns that varied considerably in temperature prior to loading,
whereas ferns in van container B were all the same temperature at loading.
After product temperatures reached the recommended shipping temperature, they
were rather uniform throughout the load mass, varying no more than 4° to 5°
(2.29 to 2.8°). No freeze or heat damage of fern was observed in either van
container in test l.

In test 2, the thermostats on van containers A and B were set at 36° F
(2.2° C) (fig. 7). Initial mean fern temperatures measured about 66° (18.9°)
and 53° (11.7°) in van containers A and B, respectively; In both van con-
tainers, the large differences between the high and low product temperatures
at loading were the result of mixed lots, some boxes precooled and others held
prior to loading at ambient temperatures. In van containers A and B, approxi-
mately 60 and 48 hours, respectively, were required for mean fern temperatures
to reach 40° (4.4°). After fern temperatures reached near the thermostat
setting in both van containers A and B, they were relatively uniform throughout
the load mass, varying no more than 4° (222) during the remaining transit
period. No freeze or heat damage was observed in either van container of this
test. Since the corrugated boxes shipped in both tests 1 and 2 arrived in good
condition and maintained excellent alinement during transit, the loading
patterns performed satisfactorily.

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In test 3, thermostats were set at 40° F (4.4° C) on van container A and
at 38° (3.3°) on van container B. Discharge air temperatures fluctuated from
17° to 39° (-8.3° to 3.9) in van container A and from 17° to 49° (28) 3mte
9.4°) in van container B. On arrival, some fern in boxes on the top layers
of both loads had freeze damage. This indicated discharge air temperatures
were too low for extended periods of time. The excessive low temperatures
and range in discharge air temperature fluctuations indicate that in this
particular test the thermostat sensing devices may not have been properly cali-
brated or that some other malfunction occurred. The boxes in both loads were
stacked in parallel air patterns and box condition on arrival was excellent.

In test 4, thermostats on van containers A and B were set at 40° F
(4.4° C) and 42° (956°): respectively. Initial fern temperatures at loading
were relatively similar, 49° (9.4°) and 43° (3.92).2 Discharge air temperatures
ranged from 33° to 45° (0.6° to Fo2) in van A and 27° to 45° (=2.8° to Jz2°)
in van B. Boxes in both loads were stacked with parallel air channels in the
third and fifth layers. The boxes arrived in excellent condition and main-
tained alinement during transit. No freeze or heat damage to ferns was
observed.

Tests 5, 6, and 7 were of single van containers shipped at different
times with thermostats set at 38° F (3.3° C). Boxes of fern shipped in each
of these test van containers were stacked in different stowage patterns.

Boxes were stacked in a parallel air channel (layers 3, 5), tight stack, and
parallel air channel (layer 3) patterns in tests 5, 6, and 7, respectively.
Mean temperature of fern in test 6 decreased more slowly during the first 48
hours than that in tests 5 and 7. This slower reduction can be related to

the tight stack pattern, which restricts the free flow of air through the load
mass. No freeze damage was observed to ferns shipped in these three tests.

The boxes arrived in satisfactory condition and the loading patterns maintained
excellent alinement.

CONCLUSIONS

The results of this study indicate that discharge air temperatures in
commercially available van containers fluctuate considerably from thermostat
settings. When relatively low thermostat settings are required (near but
above 32° F (0° C) for chilled cargo, such as leatherleaf fern, a fluctuation
below the freezing point of fern for a considerable time may cause freeze
injury. Fluctuations in discharge air temperature are usually most extreme
during the first hours after loading when product temperatures are stabilizing
near the temperature of discharge air. Varying the thermostat setting as in
these tests between 36° and 42° (292° and 5.6°) results in little degree
difference in the spread of the temperature fluctuation of discharge air. The
object then is to reduce the product temperature to recommended levels quickly
and then maintain it at the recommended shipping levels of between 34° and 40
(1.19 and 4.4°) without freeze injury during transit. To accomplish this
shippers must stow boxes in proper loading patterns, which will insure that
refrigerated air is distributed throughout the load mass and returned unre-
stricted to the refrigeration unit. The thermostat should not be set below
36° (2.2°) or above 38° (3.39). If a single thermostat setting will eliminate
confusion for operators of equipment, we suggest 37° (2.8°).

14

This series of test shipments indicates that leatherleaf ferns can be
transported to export markets in van containers and that they will arrive in
excellent salable condition.

15

APPENDIX

The information in this appendix is provided as a quick reference of
recommended handling and shipping practices that shippers should follow when
exporting leatherleaf fern in van containers. This checklist was developed
from the study described in this report and from previous research conducted
with shipping perishable cargo. 5/ 6/

(1) Quality.--Ferns shipped to export markets should be free of injury,
diseases, and pests. The fronds should be clean and free of soil and any
debris. Each frond in a given bunch should be of uniform size and color and
at the same relative stage of maturity. Most export markets utilize and prefer
the large fronds, 18-21 inches (45.7-53.3 cm) in length, but some receivers
request and use smaller fronds. It is important that frond size and quality be
agreed upon between shipper and receiver prior to shipment.

(2) Pretransit Treatment.--After harvesting, ferns should be moistened
with water and precooled to 34°-40° F Gieie 24 AoC) ae rapidly as possible.
This can best be accomplished by placing bulk lots of ferns in cold storage for
precooling before packaging. When fronds are dipped in a fungicide, this
chemical must have clearance for entry into the importing country.

(3). Packaging.--Ferns should be packaged in moisture-resistant, corrugated
fiberboard boxes, which should be either wax dipped or wax impregnated. These
boxes should be constructed of at least 275-pound (124.7-kg) test weight
material. Overfilled boxes result in damage to the ferns, and bulging causes
severe misalinement of boxes during stowage. Boxes should be lined on all sides
with perforated polyethylene that completely encloses the ferns. Perforated
liners prevent excessive drying out and will allow improved air exchange and
cooling.

(4) Van Containers.--Request newer model van containers that provide
continuous air circulation because in some older units the fan only operates
when the compressor is on.

(5) Pretransit Van Container Check.--The transport vehicle should be
checked by the shipper or his agent for cleanliness, proper refrigeration
operation, and other mechanical operations prior to dispatching the vehicle for

5/ Miller, W. R., Moffitt, T.., Risse, L.A. and Jothers. Importance
of handling and shipping practices in exporting leatherleaf fern via van
containers. South. Floral and Nurseryman Mag. 90 (1): 16, 17, 35-37.
Mar. 1977

6/ Miller, W. R., and Risse, L. A. Recommendations for handling and
shipping cut leatherleaf ferns for European markets. Fla. Ornamental Growers
Assoc. Newsletter 3, 8 pp. May 1978.

16

loading. This also applies to a second vehicle if the fern is transferred to
another van for the ocean voyage. Specifically, the following items should be
checked:
®
(a) The electrical generator unit and refrigeration system should be
placed in operation and all functions checked, including the heating and
defrost mechanisms.

(b) The thermostat should be set at the desired transit temperature
of 369-389 F (2.29-3.3° C) and the unit allowed to operate until the set point
is reached. Once the set point is reached, the unit should be observed
through several on/off cycles, in which the thermostat controls the unit
around the set point. If the indicating thermometer on the unit varies more
than + 3° from the set point, the carrier should be notified so that repairs
or adjustments can be made before the loading proceeds.

(c) All doors should close tightly and maintain an adequate seal.
(d) Ducts should be examined to be sure they are installed properly.

(e) The floor drains should be checked to make certain they are
operable and not clogged with debris.

(f) The cleanliness of the van should be verified before loading.

(g) If any of these items are not met, the carrier should be notified
and the deficiencies corrected before loading the vehicle.

(6) Transit Environment.--During transit, the recommended temperature
for leatherleaf ferns is 34°-40° F (1.1°-4.4° C) and the relative humidity
90-95 percent. The thermostat setting of the transport vehicle should be based
on the outcome of the pretransit vehicle check, but the thermostat generally
must be set from 36° to 38° (2.2° to 3.3°) to avoid product freeze damage.
Both the ferns and the transit vehicle should be precooled to the required
shipping temperature before final loading.

(7) Loading Pattern.--The most important factor in loading van containers

is to use stowage or stacking patterns that permit adequate air circulation and
distribution through the load. In conventional van containers, air channels

should be provided lengthwise through the load. This can be accomplished
either by stacking the boxes in a modified bonded-block pattern or by providing
parallel air channels in selected layers. In this way, product temperatures
will equalize with the vehicle's refrigerated air temperature as quickly as
possible and will permit fern temperatures to be uniformly maintained through-
out the load.

(8) Bracing.--Boxes should not be stacked beyond the "T" rails at the
aft end of the floor of van containers. If there is a void space between the
rear vertical surface of the load and the inside of the rear doors, bracing
should be used to keep the boxes at the rear from shifting back against the
rear doors. Shifting may cause severe restriction of air circulation around
the perimeter of the load, prevent air movement in the air channels, and thus

17

cause severe misalinement and crushing of the rear boxes. Bracing is a simple,
inexpensive device and should be used when needed.

(9) Care of Ferns During Distribution and Marketing.--Cut ferns are
highly perishable and must be handled properly during marketing. Proper
handling assures that the ferns will arrive in optimum condition and will have
a reasonable shelf life. Proper handling includes those factors previously
described. On arrival, ferns should be kept in shipping containers and held
under refrigeration during temporary storage and distribution to wholesale and
retail markets. Temperatures during this period should be maintained at
34°-40° F (1.1°-4.4° C) and fronds should not be allowed to dry out.

«U.S. GOVERNMENT PRINTING OFFICE: 1979 293-100/6220 1-3

18

U.S. DEPARTMENT OF AGRICULTURE

SCIENCE AND EDUCATION ADMINISTRATION POSTAGE ANDO FEES PAID
WASHINGTON, D.C. 20280 U. S. DEPARTMENT OF
AGRICULTURE
OFFICIAL BUSINESS AGR 101

PENALTY FOR PRIVATE USE, $300