Garlic
Allium sativum
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.
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 days.
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 types.
3. Complete
bolting types. These bolt readily, producing a scape which 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 an incomplete leaf which 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 which 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.
CLIMATIC REQUIREMENTS
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 Pacific Northwest.
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 some strains. 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 (increasing photoperiod) 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.
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 June.
Hardneck garlic is represented by varieties such as Roja, German
Red, and Valencia. Continental 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 Pacific Northwest.
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 growers producing them for fresh market.
Silverskin garlic rarely, if ever, produces seedstalks.
Further
general classifications (each with its own group of varieties or strains)
include: Rocambole, Continental (eastern European), porcelain and Asiatic
(all hardneck types).
Elephant garlic (Allium ampeloprasum) is not a true garlic
but a type of leek which 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 more tender 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
Hardneck 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 of cloves.
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.
Softneck types:
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 with "artichoke" garlic.
"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 gardeners.
PLANTING STOCK:
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 97526
- 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 97321
- 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
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 carousel plug 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 maturity.
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 reduce 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 reduced number of pounds required for planting. Cloves that are small
may not segment adequately.
For ease of digging,
and to reduce soil compaction, garlic is often grown on raised beds which
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.
SOILS
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
FERTILIZERS
The following
are general recommendations. It is advisable to submit a soil test for
each field being planted.
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:
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
effects, and recommendations for P and K.
PHOSPHORUS
Base P application
rates on soil test. Usually, 100-200 (P2O5) lb/acre. All P should be banded
at planting time.
POTASSIUM
Base K application
rates on soil test. Usually, 0-150 (K20) lb/acre. Broadcast before planting.
LIME
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 which appear
paper-like when the bulbs are dry and mature.
MICRONUTRIENTS
Apply micronutrients
only as indicated by soil test.
IRRIGATION
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 Hermiston area 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
surrounding the 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 and irrigation.
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 application.
TOPPING
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 operation using 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 partially 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 sunlight. Excessive 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 form Ag. USDA Handbook #66):
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 sprouting
(witches-brooming) and early maturity, while storage above 65 F results
in delayed sprouting and late maturity.
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. In California, 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.
PACKAGING
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.
INSECT CONTROL FOR GARLIC
THE INSECTICIDES
LISTED BELOW, TAKEN FROM THE PACIFIC NORTHWEST INSECT CONTROL HANDBOOK,
ARE FOR INFORMATION ONLY, AND ARE REVISED ONLY ANNUALLY. BECAUSE OF CONSTANTLY
CHANGING LABELS, LAWS, AND REGULATIONS, OREGON STATE UNIVERSITY CAN ASSUME
NO LIABILITY FOR THE CONSEQUENCES OF USE OF CHEMICALS SUGGESTED HERE.
IN ALL CASES, READ AND FOLLOW THE DIRECTIONS AND PRECAUTIONARY STATEMENTS
ON THE SPECIFIC PESTICIDE PRODUCT LABEL.
USE PESTICIDES SAFELY!
Wear protective
clothing and safety devices as recommended on the label. Bathe or shower
after each use.
Read the
pesticide label--even if you've used the pesticide before. Follow closely
the instructions on the label (and any other directions you have).
Be cautious when you apply pesticides. Know your legal responsibility
as a pesticide applicator. You may be liable for injury or damage resulting
from pesticide use.
Insect and Description Control, Active Ingredient/Acre
------------------------------------------------------------------------
Cutworms, Armyworms Bacillus thuringiensis - 1 to 2
Different species qt. Use a spreader-sticker
to enhance control.
Large larvae that tunnel into
bulb and chew off new shoots. permethrin - 0.1 to 0.3 lb
Mattch - see label
Lannate - 0.45 lb
Warrior - 0.015 to 0.03 lb
------------------------------------------------------------------------
Garden symphylan Telone II
Scutigerella immaculata
Telone C-17
Small, white, centipede-like
animals in soil.
------------------------------------------------------------------------
Onion thrips malathion - 1 to 2 lb
Thrips tabaci
permethrin - 0.15 to 0.3 lb
Adults are small, pale yellow to
light brown in color with feathery Warrior - 0.15 to 0.03 lb
wings. Young are pale yellowish-green
and wingless. Feed on foliage causing Mustang 1.5EW - 0.0375 to 0.05 lb
it to die.
------------------------------------------------------------------------
Wireworms Telone II
Limonius spp.
Telone C-17
Brown, jointed larvae of click
beetles. Feed on bulb and destroy crop.
For updates on above information and authors, please click on
osu.orst.edu/Dept/NWREC/vegindex.html
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