Garlic is a cool-weather perennial plant commonly planted in the cool of autumn or in early spring.
Garlic–which is often classified as an herb–is grown from cloves selected from medium to large bulbs, called heads, harvested the season before. You can plant cloves from garlic heads purchased at a grocery store or farm market as long as they have not been treated to prevent sprouting.
Garlic requires a long season for optimal yield; garlic’s long season of growth must include 6 or more weeks of chilly weather for optimal bulb or head production. Allow eight months to maturity after autumn planting for the largest bulbs; spring planted garlic (set out 6 weeks before the last frost) will reach maturity in about 100 days, but bulbs will not be as large as autumn planted garlic.
Garlic can tolerate frost, but autumn planted cloves should be protected from frost heaving and freezing ground in cold-winter regions. Garlic can be grown in containers.
Description. Garlic has solid, narrow, strap-shaped stalks that can grow 12 to 24 inches tall and 6 to 8 inches wide. Underground, garlic forms round, white papery sheathed bulbs or heads. A head is divided into a cluster of individual cloves. Garlic bulbs form 4 to 5 inches below the soil surface. Garlic flowers in spring and summer; small, white to pinkish flowers form atop globular umbels atop, a tall central stalk.
Types of Garlic: There are three botanical groups of garlic:
• Softneck garlic: The necks of this garlic type are soft and pliable at maturity. Softneck is the strongest-flavored garlic. It is less winter hardy than hardneck garlic but stores better. ‘Silverneck’ is a soft-neck suited to cool climates. ‘Red Torch’ is a softneck suited for warm climates.
• Harneck, also called Rocambole, and Spanish garlic: This garlic has a stiff central stem or neck which curls at the top forming a 360° coil. This garlic has a mild flavor. Harneck garlic is commonly left in the ground for two years before harvesting. ‘German Porcelain’ is a hard-neck type. ‘Killarney Red’ is a harneck garlic.
• Elephant garlic: Elephant garlic is not true garlic; it is a type of leek. This plant gets its name from its size; it has large fist-size bulbs weighing up to ½ pound or more. Elephant garlic has a mild flavor.
Garlic Yield. One softneck garlic head will yield 10 to 40 cloves. One hardneck garlic head will yield 4 to 12 cloves. There are about 50 cloves in one pound.
Site. Garlic requires full sun for best growth and bulb production. Grow garlic in well-drained, sandy-loam, a soil rich in organic matter if possible, but average soil will suffice. Prepare planting beds in advance by working in 1 to 2 inches of well-rotted compost. Chives prefer a soil pH of 4.5 to 8.3. Don’t plant garlic in heavy, clay, or constantly wet soil.
Garlic Planting Time. Plant garlic in the fall—as early as September in the North–for harvest the following July or August; plant garlic as late as December in the South for a harvest as early as the following May. Garlic prefers short, cool days at the start of leafy growth and later long, warm days to produce bulbs prior to harvest. For the best bulb development, planted cloves need to be exposed to chilly soil and weather—below 40°F. Autumn-planted garlic yield bigger cloves than garlic planted in spring.
In mild-winter regions, give cloves a pre-planting cold treatment by putting them in potting soil in a plastic bag and setting them in the refrigerator for 8 weeks or more. When the cloves begin to sprout, plant them out into the garden. In cold-winter regions, protect cloves from frost-heaving and severe cold by insulating the planting bed with 6 inches of straw or dry leaves after cloves have been planted 2 to 4 inches below the soil surface.
Planting and spacing. Garlic is grown vegetatively from the cloves formed in each bulb. The size of the seed clove is important to yield. A large clove will produce the largest bulbs. Small cloves will produce small plants. (The small center cloves you find in a bulb are best used in cooking and not used for planting; their yield will not be significant.) Set cloves about 2 inches deep—a bit deeper if you fear frost heaving or cold damage in cold-winter regions. Set elephant garlic cloves 4 inches deep. Always set cloves pointed end up. Plant cloves 4 to 8 inches apart in all directions. Set cloves of elephant garlic 12 inches apart.
Water and Feeding Garlic. Garlic prefers steady water, but do not saturate the soil. Garlic is shallow rooted and requires irrigation where rainfall is not adequate. Add compost to the soil in spring. Spray plants with liquid seaweed extract 2 to 3 times during the growing season. Keep nitrogen, phosphorus, and potassium moderate.
Companion plants. Beets, brassicas or cabbage family plants, celery, chamomile, lettuce, tomatoes, and strawberries. Avoid planting garlic with beans or peas. Do not follow onion family crops.
Garlic Care. Garlic requires time to develop bulbs; if plants begin to flower in spring or seed stalks begin to form, pick or break them off promptly allowing the plant to devote its energy to developing bulbs. After flowers form and stems yellow in summer, bend the stems sharply to the ground (this is called “lodging”). Lodging prompts bulb formation; bulbs will grow with little or no top growth. Stop watering about one month after lodging unless the weather is very hot and dry.
Container Growing Garlic. Garlic can be grown in containers as long as it is positioned in a warm spot and gets regular water. Because garlic requires a long growing period, you may want to interplant garlic with lettuce or another green.
Pests. Aphids, nematodes, and thrips attack garlic. Control aphids and thrips with a strong, steady stream of water or insecticidal soap. Plant nematode resistant varieties or solarize the soil to control nematodes.
Diseases. Botrytis and white rot can attack garlic; control botrytis and other molds with a commercial fungicide that contains baking soda.
Garlic Harvest. Garlic is ready for harvest when the tops have begun to yellow and are partially dry and bend to the ground or about 2 to 3 weeks after lodging (see above). Take up bulbs with a spade or spading fork or when they pull up easily from the stem.
Curing Garlic. Remove clinging soil and allow head to cure or dry for 3 to 4 weeks. Protect heads from sunburn or rainfall and allow for good air circulation during curing. Outer skins will turn papery. Discard cloves that have blue-green spots or mold. Curing is complete with the skins are dry and the necks are tight.
Storing Garlic. Store cured garlic in a well-ventilated container or nylon net bag or in a dry, cool, and dark place. Partially dried garlic can be braided into strands for short-term storage. Bulbs will start to shrink if stored at a temperature above 77°F.
Common name. Garlic
Botanical name. Allium sativum
Origin. Central Asia
Common name. Elephant garlic
Botanical name. Allium scorodoprasum
More tips at How to Grow Garlic.