Extracting and cleaning forest tree seed

Historic, archived document

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

Issued October 16, 1912.

2S DEPARTMENT-OF AGRICULTURE,
FOREST SERVICE—CIRCULAR 208.

HENRY S. GRAVES, Forester,

EXTRACTING AND CLEANING
FOREST TREE SEED.

COMPILED BY THE BRANCH OF
SILVICULTURE.

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1912.

FOREST SERVICE.

HENRY S. GRAVES, Forester.
ALBERT F, PotTrmerR, Associate Forester.
HERBERT A. SMITH, Hditor.

BRANCH OF SILVICULTURE.

W. B. GREELEY, Assistant Forester in Charge,

EARLE H. CLAPP, Forest Inspector.
SILVICS.

RAPHAEL ZON, Chief.
S. T. DANA, Assistant Chief.

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EXTRACTING AND CLEANING FOREST TREE SEED.

The extraction and cleaning of seed from cone-bearing trees are
essential steps in artificial forestation. Economical methods and de-
vices for doing this work have not yet been fully developed or stand-
ardized in the United States. Even the fundamental conditions
necessary to prevent overheating, crushing, molding, and other in-
juries to seed, in extracting and cleaning, are not thoroughly under-
stood. This is particularly true where small quantities are handled
with simple appliances. The following directions, compiled from the
experience of a number of members of the Forest Service, are designed
to meet the needs of Forest officers and others who extract and clean
seed in small amounts, without the facilities of a fully equipped plant.

STORING CONES BEFORE DRYING.

It is always preferable, especially when only natural heat is to be
used, to begin drying cones at the earliest possible opportunity.
When artificial heat is to be used finally, preliminary drying keeps
the cones in good condition and enables them to be opened more
readily later. The best method of handling cones is to spread them
on canvas drying sheets in the open as soon as they are received.
In fair weather this should always be done. If the weather is un-
favorable, cones should be spread on canvas sheets in a dry building
where plenty of air is circulating. Where there is not enough space
to do this, they should be dumped into bins separated from each other
by slat partitions set about one-half inch apart. Ventilating pipes,
through the center of each bin, will increase the air circulation.

A fair makeshift for these methods is to pile the cones in heaps
in the open or in a well-ventilated room. If in the open, they should
be covered during wet weather in order to keep them as dry as pos-
sible. In any event, the cones should be shoveled or raked frequently
to provide ample ventilation and prevent molding or mildewing.
They should not be left in tied sacks, but if this is not avoidable they
should be stored only in a dry, cool room. They should never be

_stored in dark, damp, or ill-ventilated rooms. Such conditions

almost invariably cause molding and mildewing, and may lead to pre-

mature germination. If mildewing starts, the cones should be spread

on sheets in the sun and dried as thoroughly and rapidly as possible.
5

6 EXTRACTING AND CLEANING FOREST TREE SEED.

Every precaution should be taken to keep away squirrels, chipmunks,
and other rodents. This can ordinarily be done by the use of
poisoned grain.

HANDLING CONES IN TRANSIT.

In transporting cones to the place of extraction similar precau-
tions should be taken to keep them dry and to prevent heating.
Ordinarily the best method of shipping is in sound gunny or sugar
sacks, closely tied to prevent loss of loose seed. When shipped in
carload lots stock cars should be used if possible, since these afford
the best circulation of air. If box cars must be used, the small doors
or windows in the ends of the cars should be left open. The sacks
should be stacked in rows with air spaces between them and between
the outer rows and the sides of the car. Ample space for circulation
of air should be left also between the tops of the stacks and the roof
of the car. |

Seed which has ripened naturally and which has been extracted
without having been subjected to dampness or overheating is better
than that extracted from mildewed or moldy cones. Any precau-
tions taken to avoid these unfavorable conditions will produce seed
of higher quality.

DRYING CONES BY NATURAL HEAT.
WHERE NATURAL DRYING IS PRACTICABLE.

With favorable weather conditions the seed of nearly all coniferous
species, except lodgepole pine, can be extracted by the heat of the
sun. Where this method can be used it gives the best and cheapest,
though not always the quickest, results. In the southern Rocky
Mountains it is nearly always practicable because of the clear skies,
slight precipitation, and drying winds usually prevalent from Oc-
tober to December. In the central and northern Rockies sun drying
is possible in normal seasons until about October 20. . Thereafter it
is uncertain and not to be depended upon as a method of extraction.
Sun drying is impracticable on the west side of the Cascades in Ore-
gon and Washington because of frequent rains. It can be used in
the eastern parts of these States only under particularly favorable
weather conditions. Sun drying can be used in southern California,
but in the Sierras its success is doubtful, except in particularly dry
seasons. In any locality this method may be precluded by an un-
usually wet fall, or it may be stopped in the midst of the season by
unfavorable weather.

EQUIPMENT.

To extract seed to the best advantage by sun drying the work must
be thoroughly organized in detail and the necessary equipment must

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EXTRACTING AND CLEANING FOREST TREE SEED. 6

be on hand as soon as the first cones are received. The short period
during which sun drying can be employed makes any delay in start-
ing the work inadvisable.

The first requisite is a supply of 12 by 14 feet, 8-ounce canvas dry-
ing sheets. These are used both for spreading and covering the cones.
If canvas sheets are not available wagon covers, tents, tent flies,
burlap, and heavy muslin are substitutes. A sufficient number of
drying sheets at the outset is essential, and their shortage has hereto-
fore been one of the greatest drawbacks to successful work.

If trays or raised platforms are to be used in drying, in connection
with sheets. these should also be ready when the cones are received.
One or more shovels and wooden rakes should be available.

SELECTION Or SITE.

The site for open-air drying must be carefully selected. An open
place on top of a low ridge or bench is usually preferable. Small
openings surrounded by bodies of timber are not suitable, because the
trees prevent good circulation of air. The ground should be level,
or, preferably, sloping gently toward the south, and should be thor-
oughly cleared of brush, weeds, stones, and other rubbish before work
begins. If no favorable site can be found in the neighborhood of
the collecting area or if it is anticipated that drying can not be com-
pleted before wet and cold weather sets in it may be best to select a
site at a lower altitude, where drying will be more rapid and can be
continued until a later date. The facilities for transporting the cones
must, of course, be considered.

SPREADING THE CONES.

Before spreading cones for drying it is advisable to run them over
a coarse screen to separate loose sticks, twigs, stones, dirt, needles,
and other débris. If this is not done such material becomes mixed
with the seed and makes future cleaning more difficult.

After the cones have been cleaned they should be spread on the
canvas sheets in a thin layer, ordinarily not more than one cone deep,
so that all are exposed to the air. They should be raked over at least
once a day in order that all parts of the cones may be exposed to
both sun and wind. If lack of space makes it necessary to spread
to a greater depth, the cones should be raked or shoveled at least
four times a day. Cones should never be piled deep. Considerable
seed is usually obtained from the cones by raking while drying,
especially during the hottest part of the day, but further extraction
is nearly always necessary. —

Keeping cones off the ground.—In continued dry weather good
results can be obtained by spreading the sheets directly upon the

8 EXTRACTING AND CLEANING FOREST TREE SEED.

ground. If this is done, trenching around the sheets is essential to
avoid flooding if rain occurs. Drying will, however, be much more
rapid and satisfactory if the sheets are spread on brush or platforms
raised 8 inches or more above the ground. This allows the air to
circulate beneath the sheets and prevents their drawing moisture from
the ground after a storm. In unfavorable weather it is imperative
that the sheets be raised above the ground. Platforms can be easily
constructed from refuse lumber, unedged boards, or poles. The top
of the platform can be made of boards, with or without canvas
stretched over them, or of canvas alone nailed to a framework. A
still better device is to make platforms of wire-mesh screens, with
sheets spread on the ground below to catch the seeds as they fall
through.

Drying racks——A development of this method is to build a larger
frame containing wire trays and canvas sheets below them. In one
case where this appliance was used successfully frames were con-
structed of 2 by 4 inch material, 8 feet wide, 16 feet long, and set
4 feet off the ground. The tops of these were covered with 1-inch
mesh wire netting. One foot below this was stretched a sheet of
muslin or canvas to catch the seeds as they fell through. A similar
but improved device consists of a 6 by 12 foot frame made with
posts driven into the ground and standing from 3 to 4 feet high.
This frame holds two movable trays, supported by 2 by 2 inch cross-
pieces. The upper tray is 5 feet long and 12 feet wide by 4 inches
deep; it has a wire-screen bottom, with ?-inch or 1-inch mesh. This
is to hold the cones while drying. The lower tray, which is also
4 inches deep but 8 inches wider and longer than the upper, has a
cloth bottom which catches the seeds as they fall through the wire
screen above. With species whose cones open readily, such as yellow |
pine, it is often possible to extract all of the seed in this apparatus
by stirring the cones frequently as they dry. The empty cones are
thrown out with a potato shovel. At the close of the season the racks
can be removed readily and placed under shelter. The frames are
so inexpensive, however, that they can be reconstructed each year if
necessary. They are also light enough to be moved easily from place
to place.

Drying platforms or racks should, when possible, slope slightly to
the south or southwest. This will expose them to the direct rays of
the sun during the middle and latter part of the day, when the air
is warmest.

Protecting the cones——Cones which are being dried out of doors
must be protected from dew and rain. At night and in bad
weather they may. be heaped together in the center of the sheet on
which they are spread, and the pile covered with the ends of the
sheet. This is done most effectively by taking hold of each corner of

EXTRACTING AND CLEANING FOREST TREE SEED. 9

the sheet successively and throwing the cones toward the center.
One corner of the canvas is then thrown over, nearly covering the
cones; next, the corners to the left and right of the first are folded
over; and finally the remaining corner, opposite the first, is drawn
over all and tucked under the farther edge of the pile. The four
thicknesses of canvas help to retain the heat absorbed by the cones
during the day and furnish good protection from rain. As an addi-
tional precaution the canvas folds may be weighted with rocks and
an extra sheet thrown over the pile. A sheet more than 14 feet
square is not easily handled by one man.

When cones are dried on platforms or in trays protection must be
afforded by covering with sheets of canvas, which should be large
enough to overhang the racks and protect the seed in the lower tray.
With cones spread directly upon the ground, the use of cover sheets
requires less time and labor in respreading the cones, but makes many
more sheets necessary.

Covering cones at night protects them from nocturnal rodents, as
well as from dampness. It is usually necessary, however, where
rodents are abundant, to protect the drying areas by poisoned grain.
Birds may often be frightened off by cloth streamers on small stakes,
or wires, around the sheets. When racks are used for drying, squir-
rels may be kept out by tacking sheets of tin sloping downward on
each leg of the frame. Care must also be exercised to prevent seeds
which have fallen from dried cones from being blown away by high
winds. This is best done by catching the seeds in a canvas-bottomed
tray with 4-inch sides.

Space required—The space required for spreading cones varies so
much with different species, and even with the same species in dif-
ferent localities, that it is hard to give specific definite figures. The
following table indicates the average number of square feet of drying
surface per bushel for each of the four species most commonly col-
lected, as well as the capacity of a 12 by 14 foot canvas sheet. This
applies to green cones spread thinly. As they dry their volume will
expand at least 50 per cent, bringing the cones into closer contact and
making more frequent raking necessary.

Bushels per

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For yellow pine and Douglas fir, the two chief species handled. 16
square feet per bushel will usually be needed, making it possible to
spread 10.5 bushels on each 12 by 14 foot drying sheet. To allow

58241 °—Cir. 208—12—__2

10 EXTRACTING AND CLEANING FOREST TREE SEED.

sufficient room for expansion, however, it is safer, in planning on
the number of drying sheets needed, to allow only 8 or 9 bushels to
each sheet.

Time required.—The time required for cones to open varies greatly
with climatic conditions and slightly with different species. A suc-
cession of clear, sunny days and frosty nights, with good winds, will
open cones very rapidly. In good weather mature yellow pine cones
will open in from 3 to 5 days. Under ordinary weather conditions
from 4 to 10 days are required, and in damp, stormy weather often.
as many as 15 days. Douglas fir and Engelmann spruce usually
require a day or two longer under the same conditions. Lodgepole
pine takes so much longer that sun drying is seldom attempted.
Cones picked early in the season, before they are thoroughly ripe,
open much more slowly than those picked later. |

Number of sheets needed—An estimate of the number of drying
sheets needed for 1,000 bushels of western yellow pine cones may
be made as follows: Ten bushels of cones can be spread on each
sheet; if it takes 5 days to open each batch of cones and there are 20
good drying days in the fall each sheet can be used four times. In
other words, 40 bushels can be handled on each sheet. Dividing 1,000
by this gives 25, the total number of sheets needed for the work.
Bad weather or the need of additional sheets for covers may make
this number insufficient. It is always well, therefore, to make the
estimate liberal, since lack of a few drying sheets at a critical time
may cause serious delay and even the loss of much seed.

DRYING CONES BY ARTIFICIAL HEAT.

With lodgepole pine, and with other species when weather condi-
tions are unfavorable, artificial drying must be used. This method
is quicker than drying by natural heat and is not dependent upon
the weather. It is, however, more difficult, more expensive, and
ordinarily does not yield as good seed; therefore it should not be
used except when outdoor drying is not practicable. Most of the
artificial drying is done at permanent, fully equipped extracting
plants to which cones are shipped from a large area. This circular
is designed for the smaller, temporary plants which must be handled
by less experienced men with simple applhances.

EQUIPMENT NEEDED.

Cabins.—The first essential in drying by artificial heat is some sort
of shelter which will protect the cones from weather and be sufh-
ciently tight to make it possible to raise the temperature to at least
110° F. An empty room in a cabin may serve the purpose and often
makes as satisfactory a substitute for a regular kiln as can be ob-
tained. It must have tight walls and plenty of space for trays
around the sides and for a stove. Often one room of a cabin is used
for drying and another for storing and extracting.

EXTRACTING AND CLEANING FOREST TREE SEED. r?

Tents—Large tents with high walls make fair drying rooms;
12 by 16 foot or 16 by 20 foot tents with 5 or 6 foot walls may be
_used, but larger tents have given the most satisfactory results. Dry-
ing is more difficult in tents than in buildings, but the former have
the great advantage of being readily transported from place to place
where cones are collected. Ordinarily the largest tents are used for
drying and smaller tents for storing and extracting.

Stoves.—Small, temporary drying rooms are almost invariably
heated by stoves. In buildings, box stoves equipped with drums have
been generally used with satisfactory results. In tents, low, conical
stoves have been more frequently used, but, as a rule, with poorer
results. They are cheap and easily put up, but require constarit
attention. Empty cones will not burn well in them. These are
serious drawbacks, and the use of box stoves with drums is prefareble.

Drying trays——The cones are usually spread in trays with wire bot-
toms arranged in racks along the sides of the room or tent. Trays
are generally made of 2 by 4 inch material, and vary in size from
2 by 3 to 3 by 4 feet. The larger trays are used only with hghter
cones, since they are more difficult to handle, especially where space
is limited. The bottom of the tray is wire netting, usually with a
3-inch mesh for lodgepole pine and with a ?-inch mesh for species
with larger cones. Twelve square feet of tray space hold approxi-
mately 1 bushel of cones, spread thinly. é

Cones may also be spread cn pieces of wire netting stretched hori-
zontally between the racks at intervals of 6 or 8 inches, with a vertical
strip at each end to prevent them from falling on the floor when
raked. Handling the cones is more difficult with this method, and
the apparatus is less easily transported from one place to another.
With either method a strip of canvas should be spread on the floor to
catch the seeds as they fall through the netting, unless the floor
is so smooth that seed can readily be swept from it without the
use of canvas. It is essential that the trays be far enough apart
to permit ample circulation of air. There should be a liberal supplv
of high registering thermometers to keep an accurate record of the
temperature in different parts of the drying room.

FIRE PRECAUTIONS.

With the high temperature and dry air prevailing in the kiln room,
extreme precaution must be taken to prevent fire. Where water
pressure is available, a hose should always be connected and ready
for use. Chemical fire extinguishers should be secured as additional
safeguards. If neither of these measures is practicable, several
buckets should be kept filled with water, to be instantly available.

12 EXTRACTING AND CLEANING FOREST TREE SEED.
DISTRIBUTION OF HEAT.

One of the most difficult problems in running an improvised kiln
is to maintain a constant supply of heat and distribute it evenly
through all parts of the drying room. The first step should be to
make the room, whether in a building or tent, as tight as possible,
except for the vents required for ventilation. AlIl chinks in a build-
ing should be closed completely. The next precaution is to secure
as constant temperature as possible. Wherever practicable, as hot
a fire should be kept up at night as during the day. This is particu-
larly necessary in a tent, where any dying down of the fire at night
causes the air to cool rapidly, with consequent delay and loss of time
and labor.
| The stove has ordinarily been placed in the center of the room
and approximately level with the lowest tiers of trays. This results
in much slower drying of the cones near the bottom of the room
and at a distance from the stove. Attempts have been made to
obviate this difficulty by dividing the stovepipe into sections and
carrying it through as much of the room as possible, but without
complete success. Better drying is secured in the farther ends of
the room, but the bottom remains much cooler than the top. This
difference is especially marked in tents, where cold air constantly
passes in under thé walls. With only one stove, even distribution
of heat is impossible. With stoves set at opposite ends of the tent
and connected by a single stovepipe, conditions are but little better.
In one instance where this arrangement was used, a difference of
from 20° to 30° F. was found in the temperature of the air at the ©
highest and lowest trays in a six-tier stack

One method of hastening the opening of the cones in the lower
trays is to raise them as the drying proceeds and the cones in the
upper trays are removed. This, however, requires additional hand-
ling and loss of time. A better method wherever space is available
is to place the lowest tier of trays somewhat above the stove. Room
for air circulation is essential. The tiers of trays should be at least
6 inches apart vertically, preferably 8 inches, and the same distance
from the walls. f

Heating the dry room from below.—The best method of securing
even distribution of heat, although not always practicable, is to have
the drying room heated from below. If conditions permit, excavate
under the building and place the stove below the floor. This will
not only heat the room above more evenly, but furnishes additional
space for spreading cones. The stovepipes should pass through as
many parts of the dry room as possible. Still better results will be
obtained if hot-air pipes can be conducted from the drum of the
stove into the room above, and even more heat can be made available

EXTRACTING AND CLEANING FOREST TREE SEED. 3

by inclosing the stovepipes in jackets, which need not extend farther
than the openings where the pipes pierce the floor.

IDEAL DRY HOUSE.

An ideal dry house contains three stories, built. in the side of a
hill to take advantage of gravity, and to utilize the earth which
partly surrounds the building to prevent the escape of the heat. The
cones are unloaded into the third story from a road on the hillside.
From this storeroom, or preliminary drying room, the cones are
dropped to the second floor or kiin room. The ground floor contains
the extracting room, furnace, and other equipment. The furnace may
consist merely of a large box stove, burning long sticks of wood, .
inclosed in a galvanized-iron jacket packed with mineral wool or
asbestos to prevent radiation of heat. From this jacket the heat is
conducted through two pipes into the drying room or kiln. The
heat is thus used where it is most needed, and its escape into the
space about the furnace prevented. The building can be built, if
necessary, only two stories high, in which case the cones are either
unloaded directly into the second story or kiln room, or stored on
the ground floor until ready for drying.

VENTILATION.

The proper ventilation of drying rooms, while less difficult than
the even distribution of heat, is fully as important. All undried
cones contain some moisture. As this is driven off the air becomes
more and more saturated. Saturated air not only prevents rapid
drying of the cones, but may injure the seed embryos. German ex-
periments indicate that damp cold air is much more harmful to
seeds than dry warm air. Some method of ventilation—letting in
fresh, dry air and letting out moist air—is, therefore, essential.

The method usually employed is to insert one or two ventilators
in the roof of the building or tent and also in openings near the floor
for the entrance of fresh air. The amount of air taken in and let
out can be regulated by adjustment of the ventilators. Tents are
usually so open at the bottom that it is not necessary to make spe-
cial provision for fresh air. Where the drying room is heated from
below, fresh air can be admitted through dampers or ventilators in
the jacket surrounding the stove. Vents to maintain circulation
should also be provided in the roof of the drying room.

While usually the best practicable, these methods of ventilation are
necessarily crude and wasteful. As the air cools and absorbs moist-
ure, it becomes heavier and sinks to the floor. Vents in the roof
carry off much of the hot, dry, light air which should be retained.
A certain amount of heavy moist air is, however, carried out with

14 EXTRACTING AND CLEANING FOREST TREE SEED. -

the current, and the circulation of air, so essential to drying the
cones, is maintained.

An improved method removes the saturated air directly from
the floor by pipe ventilators extending from the floor through the
roof. In one kiln, fresh air is admitted directly under a small box
stove with a heating drum placed near the center of the room. As |
this air becomes heated it rises to the ceiling, where it spreads to the
side walls and, cooling slightly, descends in a steady stream over the
trays. Each tier of trays is set a little nearer the wall than the one
above. The trays thus catch the descending current of hot air, which
flows over them. They are slightly tilted toward the center of the
room, so that as the air cools and absorbs moisture from the cones
it runs off the lower edge of the trays like water from a roof. The
saturated air is sucked up by pipe ventilators passing through the
roof and having inlets at the floor level.

APPLICATION OF MOISTURE BEFORE DRYING.

Wetting cones before drying apparently does more harm than
good with any species except lodgepole pine. Lodgepole pine cones
dipped in very hot water for not over one minute have in some cases
been found to open more readily and to give a higher yield than
unmoistened cones. This treatment, however, should be applied
only to very tight cones and should not be of sufficient duration to
add appreciably to their water content. Its only advantage is in
loosening the sealed tips of the cone scales. Experiments have also
shown that live steam applied under a pressure of one-half pound
for 30 seconds assists in opening cones without impairing the fer-
iility of the seed. Such treatment, however, is possible only at fully
equipped extracting plants.

Even with lodgepole pine, a preliminary wetting is not essential
and good results are obtained without it. Continued soaking of
cones has almost uniformly lessened the ease of extraction and
vielded seed of poorer quality. As a general rule, the cones should
be as dry as possible before they are put in the kiln. Preliminary
drying in the open or in well-ventilated storerooms will hasten open-
ing after artificial heat is applied.

TEMPERATURD REQUIRED.

The degree of heat and the length of time required to open cones
vary somewhat with different species, but still more with the con-
ditions under which the drying is done. In a well-equipped plant,
drying may be finished in less than half the time required in a tent,
even with the same temperature. It is, therefore, impossible to cite
average figures of general application. Ordinarily, the higher the

EXTRACTING AND CLEANING FOREST TREE SEED. 15

temperature the quicker the drying can be accomplished. Dry heat,
however, is more effective than moist heat, and heat that is too in-
tense is very apt to impair the fertility of the seed. This is particu-
larly true of intense moist heat. Often this injury to seed is not
appreciated at the time, since the deterioration does not become
apparent until several months later. :

The maximum temperature which should ordinarily be applied to
all species except lodgepole pine is 120° F. This can be raised safely
to 130° F. if the air is dry and good ventilation provided. Lodge-
pole cones should not as a rule be subjected to a temperature of more
than 140° F., although this can be raised safely to 150° F. under
favorable conditions. Lodgepole pine cones are hardest to open;
then come in order western white pine, western yellow pine, Engel-
mann spruce, and finally Douglas fir, which can often be dried satis-
factorily at a temperature of 110° F.

TIME REQUIRED.

At well-equipped plants lodgepole pine cones should be thoroughly
dried at a constant temperature of 140° F. in from 8 to 10 hours, and
other species at a constant temperature of 120° F. in 10 to 15 hours,
assuming that the cones are mature and moderately dry when put
into the kiln and that the room is evenly heated and well ventilated.
Under less favorable conditions these periods may be greatly in-
creased. In one instance, lodgepole pine cones dried in a tent at
140° F. took 44 hours to open. The difference was due mainly to
loss of heat in the tent and its uneven distribution. Preliminary
drying of the cones for a few hours at 80° to 100° F. has been found
an advantage. Opening will also be hastened if the cones are spread
thinly in the trays and stirred frequently, to make the drying more
uniform.

EXTRACTING SEED FROM DRIED CONES.

After the cones have been thoroughly dried, the next step is to
extract the seed. Merely to rake over the cones as they are drying
in the sun or kiln is the simplest but least efficient method. It is
most successful with western yellow pine, but even with this species
better results can usually be obtained by shaking. The practice of
placing cones in sacks and beating them with clubs to loosen the seed
has also proved unsatisfactory. It requires too much time and yields
only a little additional seed, which is apt to be of poor quality.

TRAY SHAKERS.

In nearly every case, therefore, to secure the maximum amount of
seed some method of shaking must be used to release the seeds from
the opened cones. One of the earliest and simplest devices is a tray

16 EXTRACTING AND CLEANING FOREST TREE SEED.

or frame with a wire-screen bottom, in which the cones are shaken
or worked over. The framework is usually of 6-inch boards, varying
from 3 by 6 feet to 5 by 7 feet in size. One-half inch mesh woven
wire is used for the bottom. The tray may be stationary, supported
on legs; or equipped with handles at both ends, so that it can be
shaken by two-men; or equipped with handles at one end and sus-
pended by ropes from a tree at the other, so that it can be shaken by
one man. Either of the last two devices is more satisfactory than the
first, since much more thorough shaking of the cones is possible.
A canvas sheet should be spread beneath the shaker to catch the seeds
as they fall through the screen bottom. A similar shaker, but of
different size and shape, consists of a box 30 by 18 by 18 inches, with-
out a top and with wire screen bottom. This, too, is hung from the
limb of a tree and is shaken in the same way. It contains about a
bushel of cones and has a capacity of 50-bushels a day. Wooden
blocks are often put in tray shakers to increase the jarring effect.

BOX SHAKERS.

All of these devices, while crude, can be used to advantage when
other methods are not practicable. Better results can be obtained by
the use of revolving cone shakers. These may be either box-like or
cylindrical in shape and are often known as “ churns” or “ drums.”
The box shaker has been more generally used. It may be con-
structed readily from a dry-goods box of proper size. It should be
large enough to hold from 2 to 4 bushels of cones when half full.
Four feet long by three feet square in cross section is a common size,
although both larger and smaller boxes are used with good results.
One or more sides of the box should be composed entirely of wire
screen. A frame is needed for support, and the extracted seeds fall
through to a canvas placed beneath. With most species a 43-inch
mesh is most satisfactory for the screen. With lodgepole pine a
+-inch mesh lets the seed through as readily and keeps out more
rubbish.

Half of one side of the box should be made into a hinged door
through which the cones can be placed in or dumped out of the
shaker. Lengthwise through the center of the box should be run an
axis of 2 by 4 inch or 8 by 8 inch lumber, or 2-inch iron pipe, pro-
jecting through the box and supported at both ends like a windlass.
By attaching a crank to this axle the whole box can be revolved.
The efficiency of the shaker may be increased by placing small cleats
inside the box or by adding small wooden blocks to the cones. to
increase the jarring effect. The additional devices are unnecessary
and undesirable. however, with species such as western yellow pine,
which give up their seeds readily, since it breaks up the cone scales
and makes cleaning of the seed more difficult.

EXTRACTING AND CLEANING FOREST TREE SEED. 17
CYLINDRICAL SHAKERS.

A convenient size for the cylindrical shaker is 3 feet in diameter
by 4 feet long. The ends are of wood, but the sides consist of heavy
wire screening, usually with }-inch mesh, supported by a wooden
framework, and a hinged door. An axle is put through the center
of the cylinder, a handle attached, and the entire machine set on a
sawhorse or windlass.

Of these types of shakers, the box is more easily constructed, and
is more effective with cones from which the seeds are extracted with
difficulty, since the shaking is more violent. On the other hand,
this is a disadvantage in the case of easily extracted seed, since it
breaks up the cones and increases the amount of rubbish to be removed.
Small cones, furthermore, like those of lodgepole pine, are apt to
collect in the corners of box shakers.

Shakers of both types should be revolved at a rate which will just
bring the cones to the top of the mass and then allow them to fall
straight to the bottom. The speed necessary varies with different
species, as does also the number of revolutions required to extract all
of the seed. From 206 to 40 revolutions is ordinarily sufficient to get
practically all of the good seed. Too much time should not be spent
in trying to secure every seed, since those at the extremities of the
cones, which are extracted with the most difficulty, are often imper-
fect, and their presence in good seed lowers the quality of the whole.

BARREL SHAKERS.

A barrel may be used for seed extracting in practically the same
way as the devices already described. One and a half inch iron pipe,
with a crank at one end, is run through the center of the barrel.
With this as an axis the barrel is mounted on a box about 4 feet long,
24 feet wide, and 3 feet high. Both ends of the barrel are screened,
with one screen movable to permit filling and emptying. For con-
venience in handling the seeds a tray may be fitted into the box to
catch them as they fall from the barrel. The large box is useful
not only as a means of support but also to keep the seed from blow-
mg away. A 40-gallon barrel, filled about two-thirds full, will hold
from 24 to 3 bushels of well-opened Douglas fir cones. Seed can
ordinarily be extracted thoroughly by revolving the barrel about

five minutes.
INCLINED SHAKERS.

Where seed extraction is to be conducted on a more extensive scale
a shaker capable of handling a larger quantity of cones should be
built. This is hardly worth while for less than 250 bushels of cones.
A model which has been used successfully with yellow-pine cones
consists of a wooden frame 3 feet square at the ends and 16 feet long,

18 EXTRACTING AND CLEANING FOREST TREE SEED.

over which wire screening is stretched to form a long oblong box.
The frame is held rigid with four internal X-shaped cross braces
about 5 feet apart, connected at the ends by horizontal slats or
strips. The screening is stretched horizontally from end to end of
the frame and should never be wound round the frame. The frame-
work may, of course, be constructed to fit any width of screen. The
ends of this long screened box or shaker are left open to allow the
free passage of cones. Holes are bored through the center of the
four cross braces before they are put in the frame, and when the
whole box is assembled a2-inch iron pipe, bent at the upper end so asto
form a crank, is thrust through these holes and firmly fastened to the
frame, the lower end projecting beyond the shaker for a short dis-
tance to form a support. This pipe is then set in two wooden frames
so as to allow the shaker to revolve. The lower end of the churn
should be mounted from 3 to 6 inches below the upper end, where
the cones are inserted. A chute should be constructed at the upper
end, so that cones dumped into the chute will roll directly into the
shaker. When in operation the whole machine should be set on
canvas sheets to catch the seed as it falls through the wire screens.
One man is required to revolve the shaker, another to pour in the
cones, and a third to remove the empty cones at the lower end. The
total cost of this apparatus is about $5. It has a capacity of approxi-
mately 40 bushels of yellow-pine cones per hour. With other species
which give up their seed less readily a modification of this design is
necessary to secure a more violent shaking of the cones.*

SORTING CONES.

Various appliances to separate opened from unopened cones
have been deyised. These consist of slats so spaced as to permit the
small, unopened cones to pass through while retaining the larger,
opened cones, the principle being similar to that used in machines
for grading fruit by size. Such devices generally give poor results
on account of the irregular size of both opened and unopened cones.
It is usually preferable to sort cones by hand. The small amount of
seed, however, ordinarily obtained from cones which do not open in
the first drying does not justify much expenditure for sorting.

SEED CLEANING.
IMPURITIES PRESENT.

After extraction from the cones, the seed contains impurities which
must be removed. Aside from wings, these consist mainly of broken
cone scales and needles, broken and empty seeds, resin, and dust.

1JTllustrations of this machine and of a box shaker are given in Plate IV of Forest
Service Bulletin 98, ‘“‘ Reforestation on the National Forests.”

EXTRACTING AND CLEANING FOREST TREE SEED. . - 3S

The amount of broken cone scales depends partly on the species
and partly on the treatment to which the cones are subjected during
extraction. Seed of species whose cones are very brittle naturally
contains more extraneous matter of this character. With most spe-
cies, however, it is possible to avoid breaking the cones badly if they
are shaken out rather than crushed out. The common method of
putting heavy blocks of wood in the shaker with the cones is excellent
for species whose seed is hard to extract or whose cones are tough.
For other species, however, this method is undesirable, since it not
only increases the difficulty of cleaning the seed, but is apt to injure
it. It is advisable, therefore, to use no more violence than necessary,
even if this makes extraction slower. The loss of time will be more
than offset by the greater ease of cleaning. Twigs and broken needles
can be largely kept out by screening the cones before drying is begun.

The presence of broken seeds depends chiefly on the treatment of
the cones. which has been discussed. Empty seeds are also present
in nearly all samples. Their proportion depends partly on the
species, but mainly on the season. In a poor seed year empty seeds
are usually abundant; in a good seed year comparatively rare. They
can be separated from good seed only by fanning.

The presence of resin in seed depends mainly upon the species. It
is probable, however, that crushing or overheating the cones increases
its amount. It is certain that overheating, by softening and melting
the resin, makes 1t much harder to remove. When the cones are
heated to such an extent that resin sticks to the seed, it is practically
impossible to remove it. Dust is always present to a greater or less

extent.
REMOVAL OF WINGS.

The seed of all western conifers commonly handled have wings,
which are usually, though not necessarily, removed when the seed
is cleaned. Removal of the wings probably decreases the germinative
power of seeds to a small extent. - It so greatly facilitates the ease
with which they can be handled, however, that the practice is almost
universal. In the pines, the entire wing may be detached from the
seed with comparative ease, particularly if the seeds are first mois-
tened slightly. With other species, however, the wings form part of
the seed coat, and can be removed only by actually breaking them
off. Moistening the seed is therefore of doubtful value.

By flails——One of the oldest and commonest methods of removing
Wings is to work the seed over in seamless sacks, the mouths of which
are securely tied. The sacks are beaten with light flails, usually of
leather, or kneaded with the hands and knees. Sometimes tlie sacks
are tramped under foot for a few moments, but this method impairs
the quality of the seed. With the pines, to which this method is
particularly applicable, the wings are more readily removed if the

90 -. EXTRACTING AND CLEANING FOREST TREE SEED.

seed is slightly moistened with cold water. This may be done readily
by putting the seed in a box, adding a little cold water and stirring
with a shovel.

Another application of the wet process is to pile the seed 6 or 8
inches deep on a cement or plank floor, sprinkle it lightly with water,
and then beat it energetically with leather flails. The wings can
often be removed completely with the use of very little water. A
similar method of removing the wings from pine seeds is to moisten
them slightly and then churn the mass in a ees drum until the
wings become detached.

Wet and dry process—Whenever the wet process is used, the seed
must be dried immediately so that its vitality will not be impaired.
The relative merits of the dry and wet processes depend partly upon
whether the seed is to be stored for some time or used within a few
months. In the latter case the wet process is ordinarily safe. If
the seeds are to be stored for a year or more the dry process should
be used.

By churns.—Another method of removing wings is to rub the seeds
together with a number of small wooden blocks. This may be done
by churning the seeds and wooden blocks in a box or barrel mounted
on an axle so as to be rotated, or by keeping the box stationary and
applying friction by rotating brooms nailed to a spindle running
through the center. In the latter case, if the box is tilted at a slight
angle and a hole cut in the lower end, the seeds will gradually work
out with the wings broken off.

By screens.—Still other methods depend wholly on the use of
screens. The simplest of these is to rub the seed as it comes from
the extractor over a fine screen fastened on an empty box or stout
frame. The rubbing may be done with a stiff scrubbing brush, a
block of wood covered with corrugated rubber, or a piece of tough
carpet, or the hands covered with rough gloves. As the wings are
rubbed off the seeds gradually drop through the screen, leaving a
large part of the wings and all of the coarser impurities on top.
One-sixth inch mesh is the best size for screening yellow pine and
Douglas fir seed; with lodgepole pine and Engelmann spruce one-
eighth inch mesh is preferable. The wings of the seed are more
easily removed if the seeds are moistened slightly with cold water
before screening.

With most species the first screening ordinarily does not remove the
wings completely. To secure this final removal the seeds and small
chaff coming through the first screen may be churned in a small cyl-
indrical eae covered with very fine-meshed wire, together with
several small pieces of wood. This process removes the remainder of
the wings, which, with other small particles of dirt, fall through the
screening, leaving clean seed behind.

—

EXTRACTING AND CLEANING FOREST TREE SEED. 21

By mechanical cleaners—A somewhat similar method, preferable
when the work is done on a large scale, makes use of a mechanical
cleaner or wing crusher. This consists of a rotating cylinder bear-
ing upon the outside several scrubbing brushes with stiff bristles,
which during about one-third of each revolution press firmly against
a wire screen of fine mesh. The screen against which the brushes
press as they revolve may be adjusted to regulate the pressure of the
bristles against it. The seed is dropped into the space between the
screen and the brushes, and the wings are removed as the seeds pass
under the brushes; the fragments of wings and chaff drop through
the wire screen. When using such an apparatus with pine seed a
slight moistening of the seeds with cold water is advisable before
putting them into the hopper.

FINAL CLEANING OF SEED.

The final cleaning of seed is done by screening and fanning.
Thoroughly clean seed can not be obtained without fanning. Where
no fanning mill is available, fairly clean seed can be obtained by
passing the seeds through wire screens of different sized mesh to
remove first the coarser particles, such as pieces of cone scales, twigs,
and needles, and then the finer chaff and pieces of broken wings;
and finally by winnowing the remaining seed in the wind or by
bellows or other mechanical devices. A blacksmith’s rotary blower
has been used effectively in winnowing lodgepole pine seed.

Seed may be fanned in one of the ordinary farm machines for
cleaning grain. It removes practically all broken and empty seed
as well as much of the resin and other impurities if the draft is
properly regulated and screens with the right-sized mesh are used.
It is essential that the wings be removed from seed before fanning,
otherwise many good winged seeds will be lost. Not infrequently,
particularly with poorly adjusted machines, the seed must be fanned
more than once before it is thoroughly cleaned.

Before purchasing grain-cleaning machines their adaptation to
cleaning coniferous seed must be fully determined. Many of the
ordinary machines have yielded but poorly cleaned seed with low
fertility, even after running the seed through the mill six or seven
times. This increases cost of power and labor and adds the expense
of storing and handling a considerable amount of refuse with the
seed. Two machines have proved satisfactory. One of the impor-
tant points in selecting a fanning machine is to secure screens prop-
erly perforated for the species which is to be handled.

Certain impurities, such as pieces of cone scales, resin particles,
and twigs of the same size and weight as seeds, can not be removed
ordinarily by screening or fanning. The only way to get rid of these
is to pick them out by hand, and this is seldom warranted. Such

22 EXTRACTING AND CLEANING FOREST TREE SEED.

foreign matter usually composes a very small proportion of the total
weight of seed, and its presence does little if any harm.

SEED STORING.

Wherever possible, clean seed should be stored in air-tight recep-
tacles of glass or metal. Seed stored in such receptacles retains its
vitality under any conditions of temperature and moisture much
better than in any other except cold storage, which is seldom avail-
able. Where neither of these methods of storage is available, the
seed should be thoroughly dried and stored in a dry and cool place.
Some deterioration will take place under these conditions, but ordi-
narily not sufficient within one year to be of serious consequence.

The storing of seed in cement cellars with the wings attached has:

been found by Austrian experimenters to give better results than
storage with the wings removed. It is doubtful, however, whether
the slight saving in vitality offsets the advantage of handling and
using clean seed. In every case the seed should be thoroughly pro-
tected from rodents, either by the use of poison, by being stored in
rodent-proof buildings, or by being hung in sacks out of reach.

SUMMARY.
STORING CONES.

Make all arrangements to begin drying the cones as soon as they
are received. This is necessary on account of the short season when
outdoor drying is possible.

If storage is necessary, take every precaution to prevent the cones
from heating or molding. Never store them in damp or ill-ventilated
rooms.

DRYING BY NATURAL HEAT.

Use outdoor drying whenever practicable with all species except
lodgepole pine.

Screén the cones before drying to remove needles and other foreign
matter. | |

Do not spread the cones too thickly on the drying sheets.

Protect the cones while drying from rodents and from moisture.

DRYING BY ARTIFICIAL HEAT.

Make every effort to secure even distribution of heat and good
ventilation,

Avoid sudden or extreme fluctuations in temperature.

Never let the temperature rise above 150° F. with lodgepole pine
or above 130° F. with other species.

Do not wet cones before drying, except lodgepole pine, and then
only superficially.

nil Eo

EXTRACTING AND CLEANING FOREST TREE SEED. pes

Do not pile the cones too thickly in the trays.
Have the best available apparatus for putting out fires always
ready for use.
EXTRACTING SEED.

Do not break the cone scales in raking or shaking more than is
absolutely necessary.

Extract the seed as thoroughly as possible, but do not attempt to
secure every single seed.

CLEANING SEED.
If moisture is used in removing wings, dry the seed as thoroughly
and quickly as possible.
Do not use moisture in cleaning any but pine seed.

Do not consider seed clean until wings, impurities, and empty and
broken seeds have been removed.

STORING SEED.

Store clean seed whenever possible in air-tight receptacles.

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