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David Trinklein
University of Missouri
Plant Science & Technology
(573) 882-9631

For the Love of Garlic

David Trinklein
University of Missouri
(573) 882-9631

September 8, 2022

minute read

bulbs of garlic

Loved by most yet hated by some, garlic has the ability to attract and repulse people at the same time. Having a unique aroma and taste, garlic has become one of America's favorite flavoring agents. If fact, the average American consumes six pounds of garlic each year. Although it has been revered for its medicinal properties for thousands of years, it is only recently that the true value of garlic in promoting human health has been discovered. If garlic is a condiment you simply cannot do without, September is an ideal month to plant this powerhouse of flavor in your garden.

Garlic bears the scientific name of Allium sativum. The specific epithet sativum is a Latin adjective meaning "cultivated," and most often is used botanically to designate plants with medicinal properties. A member of the Amaryllidaceae plantfamily, garlic is grouped in the same genus to which onion, leek, chive and shallot belongs.

The garlic that we cultivate today does not appear in the wild, but there is strong evidence that it originated as a chance mutation of Allium longicuspis. The latter is a bulbous plant which often is referred to as wild garlic. The mutation probably occurred somewhere in central Asia. Most scholars agree that garlic has been used as a medicinal plant and food source for over 7000 years. This makes garlic one of the most ancient of cultivated plants.

bulbs of freshly picked garlic

The average American consumes six pounds of garlic each year.

Its nutritional value along with its wide array of medicinal benefits made garlic one of the most valued plants in ancient times. Indeed, garlic is mentioned in the literature of all of the great ancient world kingdoms. For example, ancient Egyptians, during the reign of the pharaohs, fed garlic to the laborers who built the great pyramids. It was their belief that garlic would increase their strength and stamina, as well as protect them from diseases.

In ancient Greece, Hippocrates, the Father of Medicine, advocated the use of garlic as a cleansing agent, for pulmonary problems and for abdominal growths. Pliney the Elder, a noted Roman naturalist, recommended garlic for ailments such as gastrointestinal tract disorders, animal bites, joint disease, and seizures, in his book Historia Naturatis.

In ancient China and Japan, garlic was prescribed to help digestion, cure diarrhea and rid the body of intestinal worms. It also was used to alleviate depression. In India, a medical text titled Charaka-Samhita, recommended garlic to treat heart disease and arthritis.

Garlic's medicinal properties are thought to be due to sulfur-containing compounds called thiosulfinates. One of them, allicin, is produced when a sulfur-containing amino acid called alliin comes in contact with the enzyme alliinase when raw garlic is minced, crushed, or chewed. Since the enzyme alliinase is broken down by heat, cooked garlic is less effective medicinally than is fresh garlic.

The common name garlic was derived from the Old English word garleac. Literally, interpreted, the latter means "spear leek," making reference to the lanceolate shape of the plant's cloves. Today, there reportedly are about 600 cultivars of garlic available. All can be classified into two main categories: hardneck and softneck. These, in turn, can be further divided into several types.

cloves and bulb of garlic

Example of garlic cloves that comprise the main bulb.

Hardneck types (e.g., purple stripe) produce a flowering stalk (scape) which is surrounded by underground bulbs comprised of "cloves" which are the fleshy leaves that makeup bulbs. A number of hardneck types have purplish coloration on their cloves. Hardneck varieties are considered to be more flavorful and easier to peel than softneck, making them the choice of most chefs. Unfortunately, hardneck types do not store well.

bulbs of purple garlic

Example of a hardneck type of garlic which is considered more flavorful than softneck but does not store as well.

Softneck types (e.g., silverskin) generally do not flower and form seed, but often produce bulblets on their stem. They are considered to be more productive and easier to grow than hardneck varieties. Under proper conditions softneck varieties can be stored from six to eight months. Most of the garlic found at supermarkets is of the softneck type.

cloves of garlic surrounded by melons

Example of a softneck type of garlic which is more productive and considered easier to grow than hardneck types.

A cool season crop, garlic is that grows best in a sunny location in soil that is well-drained yet moisture-retentive and relatively high in organic matter. Well-rotted manure or compost is an ideal soil amendment to improve the latter in garden soils. Garlic prefers a soil pH of between 6 and 7. Liming is recommended if the pH falls below 5.8. Application rates should be based on soil test results.

Garlic normally is planted in the fall, after the weather moderates somewhat. The goal of fall planting is to allow roots to develop, but not shoots. Shoots that develop will die during the winter and the energy used by the plant to produce them will have been wasted. Late September into October is popular as a time to plant garlic in the Midwest.

Since garlic does not compete well with weeds, the site selected should be free of perennial weeds and well-tilled before planting. Plant individual cloves two to three inches below the soil line with their pointed side up. Spacing should be about six inches within rows. Cloves should not be separated from the main bulb until the day of planting. Purchase garlic cloves from a reliable seed source and do not plant garlic purchased from a supermarket.

hand planting a row of garic

Garlic cloves should be planted about six inches apart and two to three inches deep. (Credit: Rutgers University)

Garlic has moderate-to-high fertility requirements, especially for the element nitrogen. Before planting, soil should be amended following soil test results. In the absence of the latter, a general recommendation is to apply three pounds of a balanced fertilizer (e.g., 10-10-10) per 100 square feet of garden area. A supplemental application of nitrogen usually is applied as soon as the leaves emerge in the spring and again about two weeks later. Avoid late applications of nitrogen, since the latter can delay bulb formation.

As is the case with most vegetables, garlic benefits from adequate amounts of water. If natural rainfall is not sufficient, supplemental irrigation should be practiced. However, avoid applying too much water, since overly-moist soil can result in bulb rot. Also, do not irrigate garlic once the leaves begin to mature and dry.

As previously mentioned, garlic does not compete well with weeds, making the control of the latter very important. A non-selective herbicide such as glyphosate used as a "burn down" can help control perennial weeds, as can thoroughly tilling the planting site. In the spring, the use of mulch can help to both control annual weeds as well as conserve moisture.

Garlic is relatively pest-free. Insects that can become a problem include thrips (especially during dry weather), onion maggots and wireworms. Diseases that can infect garlic include botrytis, powdery mildew pink root and purple blotch. As mentioned above, bulb rot can also be a problem in wet soils. Good sanitation and crop rotation can help alleviate most pest problems.

In the Midwest, garlic usually is ready to harvest from between the second week of July through the first week of August the year following planting. Harvest date will vary according to variety. Bulbs harvested too early do not store well. In contrast, bulbs harvest after their peak maturity often causes individual cloves to "pop" out of their skin. As a general rule, begin harvesting when the lower leaves turn brown and about half of the upper leaves still remain green.

When harvesting, dig the bulb with its leaves attached. Allow harvested plants to air dry before brushing off excess soil; avoid washing newly harvested bulbs. Harvest bulbs (and their tops) should be allowed to cure for three to four weeks in a dry environment with good air circulation. This is often accomplished by tying 10 to 15 bulbs together and hanging them to cure. After curing has been accomplished, the tops can be cut off leaving about one-half inch of the stem on the bulb.

garlic curing on table

After digging in July, garlic should be cured for three to four weeks in a dry environment with good air circulation. (Credit: University of Massachusetts)

Garlic is best stored at relatively low temperatures (32° to 38° F.) under conditions of moderate humidity (e.g. 60%). Garlic can be stored at room temperatures, but dehydration will occur faster. Expected storage life depends on type. Hardneck types will store for three or four months whereas softneck types can be stored for six to eight months.

Finally, elephant garlic (Allium ampeloprasum var. ampeloprasum) is a third plant that bears garlic in its common name. Although it requires the same production conditions as garlic, it is more closely related to leek and, therefore, not a true garlic. Elephant garlic produces larger leaves and bulbs than true garlic but is milder in flavor and can be consumed raw in salads. It, however, is not considered to be a fitting substitute for garlic in dishes that call for the latter.

hands cupping a large bulb of garlic

Not a true garlic, elephant garlic develops huge bulbs with cloves that are mild in flavor.

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REVISED: September 8, 2022