Note: Information specific to the production of garlic for planting stock
or dehydration is found in the file Garlic for Production of Planting
Most of the garlic grown in the Pacific Northwest is the non-bolting
(soft-neck) type, typically
strains of California Early and California Late. The information that follows
in the next two
sections "Growth and Development" and "Climatic Requirements" is from work
done on a number of varieties by various researchers over the years, and has been
selected to relate primarily
to the temperate region garlic (bolting and non-bolting types) grown here.
The most important references relied on are those by L. K. Mann and Y. Yamada in the 1950s and
1960s, and the exhaustive review of literature on garlic that is found in the three-volume
Onions and Allied Crops edited by H.D. Rabinowitch and J.L. Brewster, CRC Press, 1990.
TYPES OF GARLIC
Two species, Allium sativum (domestic) and A. longicuspis
(wild) of garlic are recognized. They
are so similar visually that these species distinctions are not generally
used. A more useful
distinction is the classification of garlic into softneck and hardneck types.
All wild garlic is of the
hardneck type but domestic garlic may be either hardneck or softneck. Both
begin with leafy
tissue in spring but hardneck garlic will produce a seed stalk in late May or
Hardneck garlic is represented by varieties such as Roja, German
garlic may be purple striped or white, and includes many of the southern
varieties. Creole garlic is
the type grown in Mexico, South America and the Imperial Valley of California.
It is covered
with a deep purple skin, is quite late and is not suited for production in the
With some of these varieties, seedstalks may often be topped with a
cluster of small capsules
called bulbels (also referred to as bulbils, topsets or, erroneously,
bulblets). Although bulbels are
sometimes used to produce small garlic bulbs, the seedstalks should be removed
as they appear in
order to minimize yield reduction of the crop. The term bulblet is more
correctly applied to the
small round bulbs embedded in the scales of, or attached to the large main
bulb of certain cultivars
and types. Bulblets are especially common in elephant garlic.
Softneck garlic is also referred to as Silverskin, artichoke, or
Italian. Softneck types are best
represented by the varieties California Early and California Late (also
categorized as artichoke
types). Silverskin garlic may also be differentiated into many-cloved or
few-cloved varieties, and
may also be tan, all white, or purple tinged. Numerous strains exist, having
been selected over the
years by the various companies that produce them for dehydration (Creole), or
them for fresh market. Silverskin garlic rarely, if ever, produces
Further general classifications (each with its own group of varieties or
Rocambole, Continental (eastern European), porcelain and Asiatic (all hardneck
Elephant garlic (Allium ampeloprasum) is
not a true garlic but a type of leek that produces very large cloves,
often only 3 or 4 per bulb.
Several small bulblets may also develop. It produces a large seedstalk that
may be cut and sold to
florists! The tenderer, fleshy lower portion of the seedstalk is also
prized for stir-fried Oriental
dishes. Elephant garlic is not generally used for dehydration, but is
becoming popular for
"medicinal" purposes. Flavor is milder than garlic and can be slightly
bitter. The fresh market
product is sold mainly through farmers' markets or through specialty produce
stores or specialty
sections of produce supermarkets. More recently, sales to specialty
processors for medicinal or health food use have increased.
General Descriptions of Garlic Types
Rocambole, serpent, or Bavarian garlic, sandleek, Spanish shallot and
top-setting garlic. Their
distinctive flower stalks form a coil after they emerge. Blotchy-purple
coloration on wrapper
leaves, cloves brownish sometimes reddish. Cloves arranged in a circle around
the flower stalk
and are full flavored.
Roja: Symmetrical, attractive, uniformly colored brownish-red,
medium-sized bulbs. Commonly
grown by gardeners.
Continental: Purple-striped, symmetrical bulbs. Some purple coloration
Porcelain: Tight, paper-white, shiny wrappers. Plump, large cloves.
Asiatic: Uncommon in the northwest. Cloves plump and well defined.
Bulbs usually well
colored. Skins often very thick. Bulbels often dark purple.
California Early and California Late. The most common commercial garlic
grown in the Pacific
Northwest and California. Many selections and strains developed by
dehydration companies for
their own use in dehydration. Some also used for fresh market. Synonymous
"Silverskin" types: Similar to California types above except bulbs have
more but smaller cloves.
Adapted to colder areas of the Northwest. Numerous strains grown by
Many other less common "gourmet" garlics are available in limited quantities. The Garlic Store
has an extensive listing of garlic and other alliums.
GROWTH AND DEVELOPMENT
Information from various publications indicates that:
* Matured garlic cloves, planted in the fall, go through a short (about
2-week) dormant period. With adequate moisture and temperature (see below), roots emerge and leaves
sprout, and the plant goes through a period of vegetative growth. With the onset of winter,
the plant undergoes vernalization (induced to bulb and flower) by low winter temperatures.
* Although vernalized, no inflorescence or lateral buds (that later
form the bulb) are developed
until early spring with the onset of lengthening days and suitable
temperatures. Proper bulbing is
a function of adequate growth, vernalization, and subsequent growth under long
Some temperate-region varieties may be adapted to spring planting
because the long photoperiod
of northern temperate regions are adequate, even if only minimal cold
treatment has occurred.
The degree of bulbing and flower stalk formation varies considerably and with
genotype. From a
flowering standpoint, three classifications are reported:
1. Non-bolting types. These do not form flower stalks, or do so only
rarely. Only primary cloves
form (as in strains of California Early and California Late).
2. Incomplete bolting types. These usually produce a flower stalk, the
terminal of which (the
bulbils) often remains enclosed in the pseudostem. Some of these types form a
second set of
cloves within the primary cloves, and may be confused with non-bolting
3. Complete bolting types. These bolt readily, producing a scape that
terminates in an inflorescence containing sterile flowers and topsets (bulbils).
The relationship between temperature and photoperiod is complex and
variety dependent. Generally, a photoperiod longer than a critical value is
the main factor inducing
storage leaf formation after a period of cold treatment. Also, the
longer the cold treatment,
the shorter the critical photoperiod required for storage leaf induction (and
subsequent bulb formation).
A garlic bulb develops from the bud primordia (2 or 3) of the cloves
that are planted. Each bud
primordia forms between two and six growing points, each of which develops a
lateral bud which
later develop into a clove. Temperatures during growth determine the rate of
leaf growth, clove,
and flower stalk development. Clove formation in non-bolting types differs
slightly in that
lateral-bud primordia (which form the cloves), form in the axil of the
youngest 6-8 foliage leaves,
beginning with the oldest one. At maturity, these develop into cloves. The
growing point may
then either form a clove and go dormant, or form an incomplete leaf that degenerates.
A garlic bulb can therefore be best described as an aggregate of cloves
surrounded by a sheath
consisting of the basal portions of one or more mature dry leaves. Each clove
consists of a
vegetative bud and two modified mature leaves. The inner of these two leaves
forms a thickened
base that makes up the clove. The base of the outer leaf forms the dry
sheath surrounding the
clove. The blades of both these leaves abort just above the clove. The
vegetative bud is
imbedded in the clove and consists of one or two leaf initials.
Garlic grown in temperate regions such as the Pacific Northwest is
responsive to temperature and
photoperiod for proper clove and bulb formation (and subsequent seedstalk
development of some
varieties). Varieties adapted to southern latitudes, that bulb under the
temperature and short day
conditions common to those latitudes, may not bulb or segment properly in the
With varieties such as California Early and California Late, a period of
cold exposure is needed
for proper bulbing and clove development. That cold treatment is thought to
be about 6 to 8
weeks of a mean temperatures below 40 F but may be considerably shorter with
Garlic may be sensitive to a cold treatment range of between 32 and 50 F and
is sensitive either
during growth or while the cloves are in storage. Photoperiod interacts with
temperature so that
cloves held in cold storage will bulb quickly when planted in spring
resulting in small bulbs.
Bulb and clove size is related to the amount of vegetative growth that
takes place before bulb and
clove initiation occurs. This determines optimum clove storage temperature,
planting date and
associated growing temperatures and changing day length.
Cloves exposed to adequate cold treatment may have a reversion of
vernalization under water
stress and high temperatures (above 85 F) so normal bulbing does not occur.
The longer the cold
treatment, however, the more difficult it is to devernalize the plants. Also,
plants that are growing
rapidly with good soil moisture are less susceptible to devernalization.
Limited amounts of some planting stocks may be available through:
Basic Vegetable Products, POB 1071, Hanford, CA 93232
Central Oregon Seeds Inc., 1747 NW Mill St., Madras OR 97741
Filaree Farm, 182 Conconully Hiway, Okanagan, WA 98840
Garlic Growers Of Southern Oregon Inc., POB 783, Grants Pass, OR
Joseph Gubser Co., POB 427, Gilroy, CA 95020
La Marche Seeds International, POB 190, Dixon, CA 95620
Nichol's Garden Nursery, 1190 North Pacific Highway, Albany, OR
S & H Organic Acres, POB 1531, Watsonville, CA 95077
Territorial Seed Co., POB 157, Cottage Grove, OR 97424-0061
Vessey Foods, 711 McCray St., Hollister, CA
Weaver's Garlic Shedd, POB 67, Crabtree, OR 97335. Contact Mr. Gary Weaver
Planting equipment for garlic is specialized and often custom built. A Canadian company
which manufactures a planter suitable for garlic and shallots is BDK Fabrication, 240 Argyle St., Delhi, Ontario N4B 2W8.
The contact person is Mr. Don Haskins, 519-582-8348. BDK Fabrication also manufactures single and
multiple-row garlic harvesters. For small acreage plantings, a potato attachment designed to be used with a
Holland Transplanter may be suitable for use. Contact the Holland
Transplanter Co., 510
East 16th St., Holland, MI 49423-0535. Another machine is the Model 4000
transplanter from Mechanical Transplanter Co., 1150 S. Central Ave., Holland,
MI 49423. Cloves must be individually hand-fed in the latter machine.
Silver skin garlic cloves should number approximately 75-80 per pound,
while elephant garlic
cloves may be up to 4 ounces each. Clove sizes will vary from year to year as
production conditions affect bulb sizes, quality and yields.
Garlic for seed purposes should not be stored under refrigeration. When
necessary, store garlic
for seed at 50 F and maintain a humidity of 65-70%. Garlic cloves sprout most
rapidly at 40 to 50
F, hence prolonged storage at this temperature range should be avoided.
Storage of planting
stock at temperatures below 40 F may result in rough bulbs, side-shoot
sprouting and early
maturity, while storage above 65 F may result in delayed sprouting and late
Extreme care must be exercised in using pest-free planting stock. Bulbs
and cloves used for
planting can carry and transmit diseases such as Sclerotinia cepivorum
(white rot), Fusarium
cumorium, (basal rot), and possibly Botrytis allii and B.
porri. The seed may also be infected by
Penicillium, a fungus that can cause a decay of the seedpieces and
stand. Other important
pests that can be carried on the seed stock are several species of nematode
(stem and bulb). Some
of these pests may render the soil unusable for further production of garlic,
onions and related
crops. Whenever possible observe the field from which the planting stock is
to be obtained for
these and other pests. See also the section on disease and insect control.
Garlic should be planted in early fall (September or early October).
Data from California indicate
that higher yields are associated with earlier fall plantings (comparing
October and November
plantings). Although plantings have been made successfully in late winter
(February or March),
under certain conditions these later plantings may not bulb properly if growth
and cold induction
has not been sufficient before bulbing begins in May.
Plant cloves about 2 inches deep. Select healthy large cloves, free of
disease. Medium cloves
may generate the best economic return due to the increased count per pound and
of pounds required for planting. Cloves that are small may not segment
For ease of digging, and to reduce soil compaction, garlic is often
grown on raised beds that are
prepared in the fall. Beds are usually 40 inches apart center to center, with
2 rows of garlic
grown on top of each bed. Rows are spaced 12 inches apart.
Silver-skin garlic is planted at about 6-8 cloves per row-foot (12-16
plants per bed-foot) for
California Early and 8-9 cloves per row-foot (16-18 plants per bed-foot) for
California Late. This
should produce a population of about 100,000 to 150,000 plants per acre. From
1600 to 2000 lb
of California Early, and 1400-1700 lb of California Late cloves are needed to
seed an acre. The
higher populations are used for processing or planting stock purposes.
Elephant garlic is planted
at 2-4 cloves per bed foot requiring 500 to 1000 lb of cloves per acre.
Garlic will grow in almost any well-drained, friable soil, preferably
with good organic matter content. These soils allow
the bulbs to expand
without becoming misshapen. It will also aid in the soil water holding
capacity, which is
important due to the relatively restricted rooting characteristic of garlic.
Soils must have a pH
above 6.0. Ideal pH is between 6.5 and 7.0
The following are general recommendations. It is advisable to submit a
soil test for each field
Nitrogen, Fall-Planted Garlic
Apply 50-75 lb N/acre in the fall. Band the fertilizer 4-5 inches
below the soil and 1-2 inches to
the side of the row together with the needed P (see below). Care in
the timing of
N applications is important. Witches-brooming is believed to be caused
by heavy manuring
or extended periods of high soil N levels during the short days of
winter, lasting for about
one or more months, and starting just before lateral-bud formation.
In the spring, apply 100-175 lb N/acre split into 2 or 3
applications as plants begin to
grow. See also the comments in the section on N liquid fertilizers
having herbicidal effects:
Nitrogen, Spring-Planted Garlic
Since spring planting results in smaller bulbs, use 100-150 lb N/acre
depending on soil
type and variety. Apply 1/4 of the N and all the P and K at
time of planting and
the remainder of the N when the garlic is 6 inches tall. See also the
comments in the
sections below on N liquid fertilizer formulations having herbicidal
recommendations for P and K.
Base P application rates on soil test. Usually, 100-200 (P2O5) lb/acre. All
P should be banded at planting time.
Base K application rates on soil test. Usually, 0-150 (K20) lb/acre.
Broadcast before planting.
Apply lime, as indicated by soil test to bring pH above 6.0, preferably
between 6.5 and 7.0. Calcium deficiency can result in soft, watery cloves that appear paper-like
when the bulbs are dry and mature.
Apply micronutrients only as indicated by soil test.
No irrigation is necessary in fall after planting if soil moisture was
adequate at planting depth. If
not, one irrigation may be needed to establish the planting.
In spring, keep garlic growing actively. From 6-10 inches of water may
be necessary in western
Oregon in late spring and summer. Approximate summer irrigation needs for the
have been found to be: 3.5 inches in May, 5.0 in June, 7.5 in July, and 7.0 in
August. Water stress
during clove development has been implicated in witches-brooming.
Continue irrigation until cloves are well filled and bulbs are the
desired size. Examine bulbs
regularly as harvest date approaches for presence and condition of the scales
bulb. Terminate irrigation when there are 2-3 matured scales surrounding the
bulb. If irrigated
too long, these scales will deteriorate one at a time until there are none,
causing bulbs to shatter at
harvest. Garlic should not be irrigated once the tops begin to fall and
become dry. In the
Willamette Valley, irrigation is usually discontinued around mid to late June
for California Early
garlic and around July 4 for California Late Garlic.
Mid-May to mid-June is a critical period for Botrytis gray mold.
Exercise care in disease control
Soil type does not affect the amount of total water needed, but does
dictate frequency of water
application. Lighter soils need more frequent water applications, but less
water applied per
Some types of garlic produce flower stalks with small aerial bulbils.
Removal of these stalks
enhances crop maturity and yield. Research in Colorado and Washington
indicates that crop
yields (average bulb weights) can be dramatically increased (70%) by removing
these flower stalks
soon after they develop.
HARVESTING, HANDLING, AND STORAGE
Depending on the type of garlic being produced, yields can range from
5,000 to 17,000 lb/acre. Yields are dependent on planting date, plant
population and planting
stock size and quality.
Yield of elephant garlic, which is normally planted at low plant populations,
can range from 1,000
to 6,000 lb/acre. Garlic is ready for harvest when the tops become partly
dry and bend to the ground.
Although garlic can be harvested several ways, single or multiple-row harvesters can be custom built by
Krier Engineering, 4774 Morrow Rd., Modesto, CA. Contact Mr. Alex Krier, 800-344-3218, for more information.
Another manufacturer of single and multiple-row garlic harvesters is BDK Fabrication (see above under planting).
Fresh Market: Garlic intended for braiding or fresh market may be
harvested at an earlier stage
(some green color still remains in leaves) to allow for some peeling and
braiding. To loosen the
bulb, run a cutter bar beneath the bulbs. Rows may be windrowed in the same
modified potato equipment. If garlic is to be hand harvested, pull the bulbs
and gather several
rows into one windrow. If tops have not already been removed, arrange the
tops to protect the
bulbs from sunscald if the un-topped windrow is to be cured in the field. If
left in the field to dry,
remove tops and roots after they are dry and prior to storage. Leave about
0.5 inch of root and 1
inch of top. Bulbs must then be graded for market.
Garlic for processing: After the tops have dried they may be
removed by propane
flaming. Care should be exercised so that garlic bulbs are not exposed and
subjected to flaming
damage. Flailing is used to complete top removal. Garlic may be dug with a
simple potato digger
and windrowed on the soil surface for a brief (1-2 day) curing period, then
hand placed into sacks
or bins for final curing (10-14 days, or as needed) in the field. Garlic must
be protected from sun
scald especially during periods of high temperature (over 90 F) and bright
exposure to sunlight may also result in greening.
If bulbs tend to shatter, or if wrapper leaves discolor, late watering
may be the cause (see
irrigation section above). Other causes of shatter may be stem and bulb
nematode infestation or
too rapid drying of the bulbs after harvest.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Garlic for seed purposes should not be stored under refrigeration.
Optimum storage temperature
for garlic for seed is 50 F with a humidity of 65-70%. Garlic cloves sprout
most rapidly between
40 to 50 F, hence prolonged storage at this temperature range should be
avoided. Storage of
planting stock at temperatures below 40 F result in rough bulbs, side-shoot
(witches-brooming) and early maturity, while storage above 65 F results in
delayed sprouting and
Store other garlic at 32 F and 65 to 70 % relative humidity. If in good
condition, and well cured
when stored, garlic should keep for 6 to 7 months at 32 F. Relative humidity
should be lower
than for most vegetables because high humidity causes root and mold growth.
where considerable garlic is grown, it is frequently put in common storage,
where it can be held
for 3 to 4 months or sometimes longer if the building can be kept cool, dry,
and well ventilated.
Fresh market garlic is commonly packaged in cartons, holding 12 display
cartons of 1 dozen each;
10-lb cartons holding 12 tube or vexar mesh bags; packages (2-3 bulbs per
package); or, 30-lb
telescope bulk cartons.
Elephant garlic may be packaged as above, or in 5-lb or 10-lb cartons
or various count bags of
sized cloves as follows:
Clove size Bag count Bag count
5-lb carton 10-lb carton
8 cm 16-18 32-36
9 cm 13-14 26-28
10 cm 9-11 18-22
11 cm 7- 8 14-16
12 cm 5- 6 10-12
Garlic imported from Chile is packaged in 22-lb (10-kg) cartons.
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