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.  It typically has a half dozen cloves per bulb, plus or minus.  Softneck garlic dominates commodity production but in New England many growers prefer hardneck types for retail sale due to their flavor and appearance, which often includes a reddish purple clove covering versus the white color common to softneck types. Softneck garlic, which has more than twice as many cloves, generally has a longer storage life than hardneck and is easier to braid.

After centuries of cultivation garlic has lost the ability to produce seeds so it is vegetatively propagated by saving bulbs and planting the cloves.  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 select and save those that perform best.

Soil Fertility

A well-drained soil with good tilth and plenty of organic matter is ideal for garlic. 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 fertility available at that time.  The table below gives timing guidelines for use of quick release sources, especially of nitrogen. Adjust timing if using a slower release material. Also, since garlic has such an early start,  avoid fields that are slow to drain in the spring.   

PLANT NUTRIENT RECOMMENDATION ACCORDING TO SOIL TEST RESULTS FOR GARLIC
GARLIC NITROGEN (N)* LBS PER ACRE PHOSPHORUS (P) LBS P2O5 PER ACRE POTASSIUM (K) LBS K2O PER ACRE
SOIL TEST RESULTS   VERY LOW LOW OPTIMUM ABOVE OPTIMUM VERY LOW LOW OPTIMUM ABOVE OPTIMUM
Broadcast and Incorporate in fall 40 150 100 25-50 0 150 100 50 0
Sidedress in spring when shoots are 6 inches high 40 0 0 0 0 0 0 0 0

Sidedress 3-4 weeks later 

40

0

0

0

0

0

0
TOTAL RECOMMENDED 120 150 100 25-50 0 150 100 50     0

Planting

Garlic is planted in the fall since it requires a cold treatment to induce bulb formation. Planting typically occurs from October in northern New England to early November in southern areas.  The goal is to allow 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 their irrigation, mulching and weed control systems. Spacing too close can reduce bulb size while spacing too far apart reduces yield per area of land. Planting arrangements include: 2 row beds 30"  apart on center with 6"  spacing in and between rows; 3 or 4 rows per bed, with 6 to 8" between and within rows; single rows spaced 24 to 30" with 6" spacing in the row. Wide row spacing between rows allows for easy mechanical cultivation for weed control; multiple rows per bed allow for use of plastic much to control weeds.

Garlic varieties differ in size and weight of cloves; generally, there are about 50 cloves per pound of cloves. 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" deep. Only healthy-looking cloves should be planted to avoid disease and nematode problems (see below for details).

Field Culture 

A layer of clean straw mulch is typically applied to garlic at planting time to avoid soil temperature fluctuations and heaving in the winter and early spring.  The garlic will grow through the mulch in the spring.  The mulch also will help conserve soil moisture and suppress weeds. However, it may be advisable to remove mulch in a very wet spring to allow soil to dry out and thus reduce the threat of soil borne diseases. In very cold growing areas, removal of mulch can also speed soil warming and garlic growth in the spring. Because garlic is shallow rooted irrigation is very beneficial during dry periods. Removal of scapes from hardneck garlic once they fully emerge is recommended because this will improve bulb size, and there is a good market for them.

Harvest and Storage

Although variable depending on variety and growing conditions, 1 lb of garlic 'seed ' bulbs will usually yield between 4 and 8 lb at harvest.  Depending on the varieties grown and location, garlic may be ready to harvest over several weeks during July. When the lower third of leaves turn brown pull some bulbs, cut them across the cloves and look to see if the cloves have filled the skins and 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 your markets may demand it. Place the harvested plants on wire racks or tie up in bundles and hang to cure for several weeks in a dry area with good ventilation. Then cut the tops off leaving an inch or so and trim the roots closely. If necessary bulbs may be brushed or the outer skin gently rubbed off to clean them.

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