Garlic

Introduction

Garlic (Allium sativum L.) is in the onion family. For thousands of years it has been grown for culinary and medicinal uses.  Garlic grows in a wide range of conditions. While most production is in mild areas, such as California, some varieties grow well in cold climates, often with better flavor. 

Types and Varieties

There are two types of garlic. Hardneck (or topset) garlic produces false flower stalks called scapes, which are also edible. It typically has about a half dozen cloves per bulb. Softneck garlic typically has more than twice as many cloves and generally has a longer storage life than hardneck varieties.  Softneck garlic dominates commodity production, but many growers in New England prefer hardneck types for retail sales due to their flavor and appearance.  Hardneck varieties often have a reddish-purple clove covering versus the white color common in softneck types. 

After centuries of cultivation, garlic has lost the ability to produce seeds. Therefore, it is vegetatively propagated by saving bulbs and planting individual cloves from which new bulbs form. The small bulbils produced on hardneck scapes can be used for propagation, but it takes several years of planting and selection to achieve marketable size bulbs.

Although many different variety names are used in garlic commerce, recent genetic research suggests there are only about 10 major varieties of garlic. These express different characteristics from one location to another, complicating variety identification. Since there is no standardization of varieties, as with potatoes, one must take garlic variety names with a grain of salt. It's a good idea to start out with several different varieties produced in your area, selecting and saving those that perform best.

Soil Fertility

A well-drained soil with good tilth and plenty of organic matter is ideal for garlic.  Garlic has a shallow root system; excess moisture, compaction, or droughty conditions will reduce yields. The optimum soil pH is between 6 and 7. Since garlic commences growth very early in the season, it is important to have soil nutrients available at that time. The table below gives timing guidelines for use of quick-release sources, particularly for nitrogen. Adjust timing if using a slower release material. Since garlic has such an early start, avoid fields that are slow to drain in the spring

Planting

Garlic is planted in the fall since it requires a cold temperatures to induce bulb formation. Planting typically occurs from October in northern New England to early November in southern areas. The goal is to time planting for good development of roots, but not enough time for the shoots to emerge from soil before winter. Many different planting arrangements are used by growers depending on irrigation, mulching, and weed control systems. Planting cloves too densely can reduce bulb size, while spacing too far apart reduces yield per area of land. Common planting arrangements include 2-row beds 30" apart on center with 6" spacing in and between rows, 3- or 4-row beds with 6-8" in and between rows; single rows spaced 24-30" with 6" in-row spacing. Wide row spacing between rows allows for easy mechanical cultivation for weed control; multiple rows per bed allow for use of plastic mulch to control weeds.

Garlic varieties differ in size and weight of cloves; generally, there are about 50 cloves in a pound. Large cloves tend to produce the most vigorous plants and largest bulbs; therefore, small cloves are often not planted. Bulbs should be separated no more than a day or two before planting so they do not dry out. Cloves should always be planted with the root side down, so the top of the clove is 1" below the soil surface. Plant only healthy-looking cloves to avoid disease and nematode problems.

Field Culture 

A layer of clean straw mulch is typically applied to garlic at planting to avoid drastic soil temperature fluctuations and heaving in the winter and early spring. The garlic will grow through the mulch in the spring. Alternatively, garlic can be planted into plastic mulch. Either will conserve soil moisture and suppress weeds. It may be advisable to remove straw mulches in very wet springs to allow soil to dry out and thus reduce the threat of soil borne diseases. In very cold growing areas, removing mulch can also speed soil warming and garlic growth in the spring. Because garlic is shallow-rooted, irrigation is very beneficial during dry periods. 

Clipping scapes from hardneck garlic once fully curled, just below the curl, has been found to improve bulb size. Scapes are edible, and can be sold and used as a garlic-flavored vegetable similar to scallions.

Harvest and Storage

Although variable depending on variety and growing conditions, 1 lb of garlic 'seed' bulbs will usually yield 4-8 lb at harvest. Garlic may be ready to harvest over several weeks during July. When the lower third of leaves turn brown, it is advisable to pull several bulbs to check for maturity. Cut the bulbs in half width-wise, and check whether cloves have fully filled out within the skins. If so, they are ready to harvest. Pull, dig, and/or undercut the bulbs to remove them. Unless a lot of soil is adhered to the bulbs, they do not need to be washed at harvest (although some markets may demand it). Place the harvested plants on wire racks or tie in bundles for hanging to cure for several weeks in a dry area with good ventilation. After curing, tops can be cut to leave about an inch remaining, and root should be trimmed closely. If necessary, bulbs may be brushed or the outer skin gently rubbed off to clean them.

Seed garlic should be stored at 50ºF with relative humidity of 65-70%. Cloves sprout most rapidly between 40-50ºF. Garlic for table stock should be stored at 32ºF and 65-70% relative humidity. Well-cured bulbs stored at proper conditions should keep for 6-7 months. Relative humidity in storage is lower than for most vegetables because high humidity causes root growth and mold.