Horticulture Production Guides
Garlic
College of Agricultural Sciences
Department Plant, Soil, and Agricultural Systems
Alan Walters
SIUC Horticultural Factsheet 5
Garlic (Allium sativum) is an excellent There are distinct types within each garlic
crop to promote as a local specialty, since subspecies. Hardneck types include
locally grown garlic is a popular produce rocambole, purple stripe and porcelain.
item at farmer’s markets and other similar Rocamboles have parchment skins that are
markets in the lower Midwest. Garlic is one much thinner than softnecks; although the
the most widely used culinary herbs and thin skins make peeling easier, they don’t
has recently gained additional attention store well. Rocambole garlic usually has
as a potent medicinal herb. Garlic is a up to a dozen cloves of a tan or brownish
popular vegetable/herb since consumers color. Purple striped garlic is highly
are familiar with its use as an ingredient in distinctive because of its bright purple
various culinary dishes. coloring or markings. Porcelain garlic has
only a few very large cloves (with as few as
Garlic is one of the easiest vegetables four) per bulb. ‘Spanish Roja’, ‘Carpathian’,
to grow in the Midwest due to the lack ‘Music’ and ‘Persian Star’ are hardneck
of significant disease and insect pest cultivars suited to the lower Midwest
problems. Garlic is highly adaptable to environment.
sustainable production or organic systems
due to the low inputs required, as adequate Softnecks includes both silverskin and
crops can be produced with little added artichoke types. The silverskin is the type
fertilizers or pesticides. The crop has great of garlic most often found on supermarket
potential for local market sales as growers shelves due to their long storage life,
can obtain a reasonable return on small and can be stored for about eight months
investments, since few off-farm inputs are without significant amounts of decay. They
required to produce the crop. There is great are the most popular garlic for braiding
potential to add this easily grown, highly since they have sturdy necks. Silverskins
sustainable crop to local direct marketing have smooth, silvery, and shiny white skins
systems. with cloves that tend to be symmetrical in
shape. The bulbs are composed of many
Garlic is well adapted for production in small cloves. Although softneck garlic
the lower Midwest. Allium sativum can be types like ‘Idaho Silverskin’ will produce
divided into two subspecies: ophioscorodon under the lower Midwest climate, they are
(hardneck garlic) and sativum (softneck not as cold hardy and may be damaged by
garlic). Hardneck types generally perform excessively cold winters. The artichoke type
better in colder climates, and the cloves has several overlapping layers of cloves
are typically larger and easier to peel. that tend to be very difficult to peel. Bulbs
Hardnecks produce only a few large, usually contain about 3 to 5 clove layers
uniformly-sized cloves per bulb, and the containing 12 to 20 total cloves. Outer
cloves encircle the central stalk only once. cloves are fat and rounded but irregularly
Softnecks have 3 to 6 clove layers that shaped, while inner cloves are much
encircle the stem, with about 12 to 25 smaller.
cloves per bulb; the outer cloves are large
while inner cloves are small and thin.
Planting Scape Development overtake young garlic plants and cause
significant yield and quality loss. Since garlic
Garlic is typically propagated by planting
bulblets (or cloves). The size of the clove is
and Removal is planted in the fall and harvested about 8
Garlic will often put up a tall, woody flowering to 9 months later, various winter and summer
an important consideration when selecting stalk (or scape) that grows bulbils at the top. annual weeds compete with garlic over this
planting stock. The bulb must be broken Hardneck garlic types will produce a scape, period of time. Mulching of new plantings has
into individual cloves. Garlic cloves should whereas softneck types do not. Flowers on already been briefly mentioned as a way to
be graded for both size and quality prior to these scapes generally abort and form bulbils, control weeds, and the use of straw mulch
planting, with diseased, small, soft, damaged, which are small, aerial cloves that can be will greatly reduce weed pressure. The mulch
or discolored cloves discarded. The cloves used for propagation. However, if planted, is often removed in the spring to allow the
should be planted with the basal plate-side bulbils will take up to two seasons to produce soil to warm up and then placed back around
down. Under lower Midwest conditions, the mature bulbs. If a garlic plant is allowed to plants several weeks later. A few soil-applied
cloves should be planted about 1-2 inches put energy into these bulbils, the bulb forming and post-emergence herbicides are registered
deep; and where winters are more severe, below the ground will be about one-third for use on garlic to control both grasses and
they should be planted about 2-4 inches deep. smaller than if the scape is removed. It is broadleaves.
Fall planting is recommended for garlic, best to cut scapes and remove when they are
as garlic must go through a cold period to first developing on the plant. Harvest and Storage
produce the highest yields as well as for the
development of cloves on the bulb. October Irrigation Determining the proper time to harvest is
very important, as over-mature garlic cloves
is a good month to plant garlic, as it will One inch of water per week, via natural rainfall
will begin to crack apart while still in the
allow sufficient time for some root and foliage or supplemental irrigation is needed for
ground. When the leaves start turning brown
development before the ground freezes. Garlic optimal garlic growth. Drip or trickle irrigation
in late June, gently dig or pull up bulbs. When
should be planted in the fall about 6 to 8 is recommended as the supplemental water
the bulbs are fully developed, the outer skin
weeks before the ground freezes. Fall-planted source. Garlic has a relatively shallow root
should be tight around the cloves. However,
garlic will grow quickly once the weather system and is sensitive to dry soil conditions.
about two weeks prior to garlic harvest, do not
warms in spring. The most critical stage for irrigation needs
irrigate and allow the soil to dry out around
is during bulbing (mid-May to late June in
plants. In smaller plantings, garlic can easily
Garlic is often planted in 6 to 8 inch high the lower Midwest). Insufficient irrigation or
be dug with a garden or potato fork. However,
raised beds to provide easier digging of bulbs rainfall during this stage will result in smaller
bed lifters, potato diggers, subsoilers, and
and better soil drainage. Individual rows need bulbs. However, irrigation should be stopped
other purchased or homemade extraction
to be 12 to 36 inches apart (depending on about two weeks before harvest to prevent
devices can be used to harvest garlic from
whether a raised bed is utilized), with garlic bulb diseases and discolored bulb wrappers.
larger acreages. Damaged or diseased garlic
plants spaced about 12 inches apart in-
the-row. Mulching of garlic with an organic
Pest Management should be immediately discarded. Harvested
Although, insects and diseases cause plants and bulbs should be placed in a cool,
material such as wheat straw soon after dry location that has good air circulation to
minimal problems on garlic grown in the
planting will help improve winter survival, dry for about 2-3 weeks. Once plants have
lower Midwest, weed control is essential to
conserve soil moisture, suppress weeds, and dried, most dead foliage can be clipped off
achieving productive garlic yields. However,
prevent soil erosion. Garlic should emerge with the stem, only leaving about ¼ to ½ inch
there are many insect pests that will attack
through an inch or more of mulch with no of the stem with the bulb. At this time, the
garlic, such as thrips and onion maggots.
problem. However, try to avoid planting garlic soil should be shaken from plants, cleaned
Onion thrips are probably the most common
in areas that have poor water drainage. to remove excess scales and placed in a cool
insect pest that attacks garlic. The nymphs
and adults scrape the outer surface of the location. Garlic should keep for 6 to 7 months
Fertilization leaf, and when damage is severe, the entire if it is stored at 32° F and at 65 to 70 percent
Garlic will grow in almost any well-drained, plant may wilt and die. Onion thrips often relative humidity. Garlic for long-term storage
friable soil and a pH of 6.8 to 7.2 is optimal. migrate to garlic from weeds surrounding or for next year’s planting stock should not be
Garlic is a heavy feeder and about 100 lbs N, fields. Since adults and nymphs inhabit washed.
200 lbs P2O5 and 200 lbs K2O per acre is weedy areas surrounding fields, these areas
needed. Broadcast and incorporate about 25 should be kept weed-free to reduce thrips
lbs N and 50 lbs of each P2O5 and K2O per infestations. After the crop is harvested,
acre before planting in the fall. Apply about 40 the tops should be piled together in some
lbs N and 100 lbs of each P2O5 and K2O per manner and burned to reduce over-wintering
acre when garlic begins to grow in the spring populations.
(March), and split the remaining amounts of
N, P2O5 and K2O at two sidedressings about 3 Certain types of diseases, such as Alternaria
and 6 weeks after the early spring application. Purple Blotch, Botrytis leaf blight, and Downy
mildew, can devastate garlic under specific
Avoid N applications when the bulbs begin to Support provided by the College
enlarge, since it will encourage excessive leaf environmental conditions. Cultural practices,
of Agricultural Sciences, the
growth at the expense of bulb size, and also such as planting certified disease-free cloves,
using crop rotations away from other Allium Department of Plant, Soil and
within 2-3 weeks of harvest.
spp. and proper field sanitation methods (e.g., Agricultural Systems, and the
removal of diseased foliage from the field Illinois Council on Food and
after harvest) will reduce disease problems. Agricultural Research (C-FAR).
Garlic is a poor competitor with weeds, and
Published June 2007
unless weeds are controlled early, they will