Garlic (Allium sativum) is an extremely popular garden plant because of its use for flavoring dishes, as well as its ease of care and growth. It is traditionally planted in autumn and harvested in mid-summer. This plant is also called the stinking rose, and it is useful as an insect repellent in gardens. Garlic is important to Korean creation myths, and is believed to ward off vampires and other spirits in European folklore.
I. Appearance and Characteristics
Garlic (Allium sativum) is a species of bulbous flowering plant in the genus Allium. Its close relatives include the onion, shallot, leek, chive, Welsh onion, and Chinese onion. It is native to South Asia, Central Asia and northeastern Iran.
The word garlic derives from Old English, garlēac, meaning gar (spear) and leek, as a ‘spear-shaped leek’.
Allium sativum is a perennial flowering plant that grows from a bulb. It has a tall, erect flowering stem that grows up to 1 m (3 ft). The leaf blade is flat, linear, solid, and approximately 1.25–2.5 cm (0.5–1.0 in) wide, with an acute apex. The plant may produce pink to purple flowers from July to September in the Northern Hemisphere.
The bulb has a strong odor and is typically made up of 10 to 20 cloves. The cloves close to the center are symmetrical, and those surrounding the center can be asymmetrical. Each clove is enclosed in an inner sheathing leaf surrounded by layers of outer sheathing leaves. If garlic is planted at the proper time and depth, it can be grown as far north as Alaska. It produces hermaphroditic flowers. It is pollinated by bees, butterflies, moths, and other insects.
Garlic is easy to grow and can be grown year-round in mild climates. While sexual propagation of garlic is possible, nearly all of the garlic in cultivation is propagated asexually by planting individual cloves in the ground. In colder climates, cloves are best planted about six weeks before the soil freezes. The goal is to have the bulbs produce only roots and no shoots above the ground. Harvest is in late spring or early summer.
Garlic plants can be grown closely together, leaving enough space for the bulbs to mature, and are easily grown in containers of sufficient depth. Garlic does well in loose, dry, well-drained soils in sunny locations, and is hardy throughout USDA climate zones 4–9. When selecting garlic for planting, it is important to pick large bulbs from which to separate cloves. Large cloves, along with proper spacing in the planting bed, will also increase bulb size. Garlic plants prefer to grow in a soil with a high organic material content, but are capable of growing in a wide range of soil conditions and pH levels.
There are different varieties of garlic, most notably split into the subspecies of hardneck garlic and softneck garlic. The latitude where the garlic is grown affects the choice of type, as garlic can be day-length sensitive. Hardneck garlic is generally grown in cooler climates and produces relatively large cloves, whereas softneck garlic is generally grown closer to the equator and produces small, tightly packed cloves.
Garlic scapes are removed to focus all the garlic’s energy into bulb growth. The scapes can be eaten raw or cooked.
II. How to Grow and Care
Sunlight
While it may be surprising for a plant that grows primarily underground, garlic loves light. To ensure the best chance at growing success, plant your garlic in a spot that receives full sunlight for at least six to eight hours a day.
Temperature and Humidity
Garlic is a very hardy plant, and it actually grows best through the colder winter months. That being said, be sure to plant your garlic about a month before the first hard frost in fall. Additionally, garlic has no special humidity requirements; It is often already harvested before the peak of summer heat and humidity.
Watering
True to its easy-going nature, garlic doesn’t have a ton of water requirements. It generally likes its soil moist and should receive around an inch of water per week, with a slight increase if the weather is especially warm. Keep the soil evenly moist throughout the first part of the growing season, but allow the soil to go dry for two or three weeks before harvesting—if conditions are too wet near harvest time, mold can grow.
Soil
One of the most important factors in successfully growing garlic is to start with nutrient-rich soil. It should also be moist but well-draining, with an ideal pH of 6.0 to 7.0. It helps to add a layer of mulch atop your soil after planting to safeguard the bulbs, conserve moisture, and prevent the growth of weeds.
Fertilizing
The use of fertilizer can be beneficial when growing garlic. Mix a slow-release organic fertilizer blend into your soil as you plant your garlic in the fall. Then, when the leaves begin to grow in the spring, feed the soil surrounding your plantings with a fertilizer blend high in nitrogen.
How to Grow Garlic in Pots
If you want to try growing a hard-to-find garlic variety, try growing garlic in containers. Plant garlic in containers at the same time you would plant garlic in the ground: before the first freeze when the soil is cool. Choose a large container of any material with lots of drainage holes, or use a large grow bag. Fill it with high-quality potting mix, a slow-release fertilizer, and place cloves in the mix with the pointy end up. Keep the pot in a spot with six hours of direct sunlight, keep the soil moist but not soggy, and you’ll be on your way to harvesting scapes and bulbs.
Pruning
Many garlic growers recommend cutting off the scapes, or topsets, of the garlic plants as soon as they start to curl, to conserve energy for the bulbs. Others prefer to leave the scapes intact because they feel it helps the bulbs in storage. Some take a middle-ground approach and cut off the scapes before they turn woody, when they are still good for cooking.
Propagation
There is nothing easier to propagate than garlic. Simply put aside a few top-quality bulbs to plant in the ground or in a container the next season. Store bulbs for replanting at room temperature, with fairly high humidity of about 70 percent.
Overwintering
Garlic planted in the fall will naturally overwinter to be ready for a spring or summer harvest. The best way to overwinter your garlic plants is to water the plants well after planting and then cover them with 6 inches of straw mulch. The mulch will keep the ground moist, stop soil heave, and stop the growth of spring weeds.
Pests and Diseases
While a fairly hardy crop, garlic does have to contend with a few pests and diseases throughout its lifespan.
Nematodes can be a chronic problem for garlic. These microscopic worm-like creatures live inside the garlic plant itself, eating it while reproducing. Nematodes don’t need water to survive and can live in the surrounding soil for several years. A nematode infestation can build up for several seasons without much damage and then strike and take out an entire crop. To control nematodes, make an effort to plant clean stock, inspect growing plants frequently, and remove any plants that look diseased.
Onion thrips have also been known to plague garlic. Thrips have rasping-sucking mouthparts that first damage the leaves then suck up the seeping plant fluid. Severe damage can cause the garlic plant to wilt and die. To control thrips, keep areas free of moist, wet mulch that provides breeding areas, and trap the insects with sticky traps.
White rot fungus, which typically develops in the middle of the season, is among the most serious diseases garlic can face. It infects the plants, turning the leaves yellow and causing them to wilt and die back. As the roots rot, infected plants can uproot easily. Be sure you obtain cloves from certified disease-free stock because once a field has been infected with white rot fungus, it can take decades for the infection to completely clear.
III. Uses and Benefits
Medicinal uses
- Cardiovascular
As of 2016, clinical research found that consuming garlic produces only a small reduction in blood pressure (4 mmHg), and there is no clear long-term effect on hypertension, cardiovascular morbidity or mortality. A 2016 meta-analysis indicated there was no effect of garlic consumption on blood levels of lipoprotein(a), a biomarker of atherosclerosis.
Because garlic might reduce platelet aggregation, people taking anticoagulant medication are cautioned about consuming garlic.
- Cancer
Two reviews found no effect of consuming garlic on colorectal cancer. A 2016 meta-analysis of case-control and cohort studies found a moderate inverse association between garlic intake and some cancers of the upper digestive tract.
- Common cold
A 2014 review found insufficient evidence to determine the effects of garlic in preventing or treating the common cold. Other reviews concluded a similar absence of high-quality evidence for garlic having a significant effect on the common cold.
Culinary uses
Garlic is widely used around the world for its pungent flavor as a seasoning or condiment.
The garlic plant’s bulb is the most commonly used part of the plant. With the exception of the single clove types, garlic bulbs are normally divided into numerous fleshy sections called cloves. Garlic cloves are used for consumption (raw or cooked) or for medicinal purposes. They have a characteristic pungent, spicy flavor that mellows and sweetens considerably with cooking. The distinctive aroma is mainly due to organosulfur compounds including allicin present in fresh garlic cloves and ajoene which forms when they are crushed or chopped. A further metabolite allyl methyl sulfide is responsible for garlic breath.
Other parts of the garlic plant are also edible. The leaves and flowers (bulbils) on the head (spathe) are sometimes eaten. They are milder in flavor than the bulbs, and are most often consumed while immature and still tender. Immature garlic is sometimes pulled, rather like a scallion, and sold as “green garlic”. When green garlic is allowed to grow past the “scallion” stage, but not permitted to fully mature, it may produce a garlic “round”, a bulb like a boiling onion, but not separated into cloves like a mature bulb.
Green garlic imparts a garlic flavor and aroma in food, minus the spiciness. Green garlic is often chopped and stir-fried or cooked in soup or hot pot in Southeast Asian (i.e. Vietnamese, Thai, Myanmar, Lao, Cambodian, Singaporean), and Chinese cookery, and is very abundant and low-priced. Additionally, the immature flower stalks (scapes) of the hardneck are sometimes marketed for uses similar to asparagus in stir-fries.
Inedible or rarely eaten parts of the garlic plant include the “skin” covering each clove and root cluster. The papery, protective layers of “skin” over various parts of the plant are generally discarded during preparation for most culinary uses, though in Korea immature whole heads are sometimes prepared with the tender skins intact. The root cluster attached to the basal plate of the bulb is the only part not typically considered palatable in any form.
An alternative is to cut the top off the bulb, coat the cloves by dribbling olive oil (or other oil-based seasoning) over them, and roast them in an oven. Garlic softens and can be extracted from the cloves by squeezing the (root) end of the bulb, or individually by squeezing one end of the clove. In Korea, heads of garlic are heated over the course of several weeks; the resulting product, called black garlic, is sweet and syrupy, and is exported to the United States, United Kingdom, and Australia.
Garlic may be applied to different kinds of bread, usually in a medium of butter or oil, to create a variety of classic dishes, such as garlic bread, garlic toast, bruschetta, crostini, and canapé. The flavor varies in intensity and aroma with the different cooking methods. It is often paired with onion, tomato, or ginger.
Immature scapes are tender and edible. They are also known as “garlic spears”, “stems”, or “tops”. Scapes generally have a milder taste than the cloves. They are often used in stir frying or braised like asparagus. Garlic leaves are a popular vegetable in many parts of Asia. The leaves are cut, cleaned, and then stir-fried with eggs, meat, or vegetables.
Garlic powder is made from dehydrated garlic and can be used as a substitute for fresh garlic, though the taste is not quite the same. Garlic salt combines garlic powder with table salt.
Spiritual and religious uses
Garlic is present in the folklore of many cultures. In Europe, many cultures have used garlic for protection or white magic, perhaps owing to its reputation in folk medicine. Central European folk beliefs considered garlic a powerful ward against demons, werewolves, and vampires. To ward off vampires, garlic could be worn, hung in windows, or rubbed on chimneys and keyholes.
In the foundation myth of the ancient Korean kingdom of Gojoseon, eating nothing but 20 cloves of garlic and a bundle of Korean mugwort for 100 days let a bear be transformed into a woman.
In celebration of Nowruz (Persian calendar New Year), garlic is one of the essential items in a Haft-sin (“seven things beginning with ‘S’”) table, a traditional New Year’s display: the name for garlic in Persian is سیر (seer), which begins with “س” (sin, pronounced “seen”) the Perso-Arabic letter corresponding to “S”.
In Islam, it is recommended not to eat raw garlic prior to going to the mosque. This is based on several hadith.
Other uses
The sticky juice within the bulb cloves is used as an adhesive in mending glass and porcelain. An environmentally benign garlic-derived polysulfide product is approved for use in the European Union (under Annex 1 of 91/414) and the UK as a nematicide and insecticide, including for use in the control of cabbage root fly and red mite in poultry.
IV. Harvesting and Storage
You’ll know it’s time to harvest your garlic when the majority of the bottom leaves have turned brown, which usually happens by mid to late summer, but you may be able to do this in the spring, too. Dig up a test bulb or two to determine maturity—the garlic should be well-wrapped but not split.
To harvest, push a garden fork straight down into the soil about 6 to 8 inches away from the plant. Angle the fork so that it goes under the bulb and lifts it out of the ground. Don’t pull the bulb out by its leaves, or you risk breaking the bulb off. Use caution because garlic bruises easily.
Brush off any soil clinging to the bulbs. Allow the bulbs to cure or dry for three to four weeks in either a well-ventilated room or a dry, shady spot outside. Once the tops and roots have dried, they can be cut off. You can also further clean the bulbs by removing the outer skins. Just be careful not to expose any of the cloves.
Harvested garlic likes to be stored in cool temperatures, as low as 32 degrees Fahrenheit. The softneck varieties may last up to eight months. Hardneck varieties may dry out, sprout or go soft within two to four months. Keeping hardnecks at 32 degrees Fahrenheit sometimes helps them survive for up to seven months without deteriorating.