EAST LANSING, Mich. — Garlic falls into two broad categories: softneck and hardneck. Softneck varieties have a flexible stalk that is an extension of the papers that wrap the cloves. This flexible neck dries down quickly and can be braided or cut for sale. Hardneck varieties are characterized by their stiff stalk that extends from the bottom plate of the garlic bulb to the top of the plant. This stalk produces a scape in early summer, which is similar to a flowering head, though instead of forming a flower, it forms a bulbil with small, genetically identical cloves that can self-sow to produce the next generation. However, most growers will remove these scapes to redirect energy downward, allowing for larger bulb formation. These scapes can be snapped off or cut above the top leave and eaten or sold as a garlic substitute.
Softneck and hardneck garlic can be further divided into different families, each of which is identified by its clove formation and flavor profile. There are numerous families of garlic, but below is a list of the most common:
|Productive and easy to grow, artichoke varieties are very common. They typically consist of an outer row of large cloves with several inner cloves of a smaller size. The flavor of artichoke garlic can range from spicy to mild.|
|Silverskin||Silverskin garlic is some of the longest lasting in storage. Because of this, they are typically the most common to find in the supermarket. Similar to artichoke varieties, silverskin garlic has 12-20 cloves arranged in multiple layers. Also like artichokes, the flavor is wide ranging among varieties.|
|Porcelain||Porcelain garlic is identified by its four large, symmetrical cloves around the central stalk. The cloves can reach impressive sizes, which are a joy to cook with, but lead to fewer plants per pound of seed. Porcelain garlics have great flavor, balancing earthiness with strong heat.|
|Rocambole||Known for their excellent, full-bodied flavor, rocamboles are sought out by chefs and processors. They have 6-11 large, easy to peel cloves, though they have a shorter shelf life than other varieties. They can be identified by their scapes, which form a double loop as they form.|
|Purple Stripe||Purple stripe garlics earn their name by their beautifully colored papers that feature purple stripes and splotches that can vary with variety and weather. They feature 8-12 cloves per bulb, with slightly smaller cloves than rocambole varieties. They have a moderate storage life of six months.|
Garlic benefits from rich, well-drained, near neutral soil, but can survive in a wide range of soil types. Softneck varieties tend to be more forgiving, but all garlic can succumb to rot when drainage is inadequate. A chisel plow or Yeoman’s plow can be used to ensure adequate drainage, especially when set up to break up the soil at each row position. Alternatively, a cover crop rotation including tillage radishes and a high-yielding legume improve drainage and provide nitrogen credits. Garlic benefits from heavy fertilization – 125 pounds of nitrogen, 150 pounds of phosphorous and 150 pounds of potassium per acre for maximum yields. Nitrogen should be applied at planting (75 pounds), at 6-inches of growth (25 pounds) and right before scape emergence (25 pounds). Compost can be applied to add fertility and organic matter, though it should be analyzed to better understand what is fertility it provides. Remember, before applying any fertility to a crop, soil testing should be done to ensure proper fertility application.
Garlic can be planted on bare soil or into plastic mulch in far northern climates. Black and green plastic mulches can help retain moisture and boost soil temperatures in the spring. In warm climates, bare soil production systems are recommended to ensure proper soil temperatures for emerging garlic.
Garlic heads must be broken apart into individual cloves a few days prior to planting. Cloves should be graded and selected to achieve optimum head size. Large cloves tend to produce larger heads. The number of plants per pound of seed is variety dependent, but a rough guide is provided below:
|Garlic Variety||Average Plants per pound of seed|
Garlic is typically planted in rows six to 12 inches apart, with individual cloves set four to eight inches apart in-row. Larger bulbs result from greater spacing, but this will result in fewer plants per acre. Cloves are planted one to two inches deep with the clove oriented with the growth plate down.
Planting should be done two to four weeks before a hard freeze settles in. In Michigan, this is in October-November. Garlic needs to be planted early enough to allow for adequate root growth, but aboveground growth is not ideal. In areas with limited snowfall, two to four inches of straw mulch should be applied post-planting. Growers in high snowfall areas can sometimes utilize the snowpack as effective mulch, though most growers continue to mulch to minimize risk of freezing planted cloves.
Garlic is a poor competitor against weeds, so proper steps must be taken prior to planting to minimize weed pressure. Stale bedding for two to four weeks prior to planting and using clean, weed-free straw mulch can greatly reduce weed pressure. Mulch can be removed in the spring to allow for mechanical cultivation, though irrigation needs may increase as a result.
In order to achieve maximum bulb size, scapes should be removed as soon as possible on hardneck varieties, and soil should be consistently moist throughout the production cycle. An inch of water per week throughout dry spells will allow for maximum growth.
Garlic is ready for harvest when five to seven leaves have yellowed. Each of these leaves correlates with a wrapper on the bulb. Late harvests, in which leaves have senesced, yield fewer wrappers and poor storage life. Harvest usually occurs in mid-June to mid-July in Michigan.
Garlic can be lifted with an undercutter bar or dug by hand. Care should be taken to avoid damage to the bulbs during harvest.
If storage is required, garlic must be cured properly. Curing garlic can be done by hanging garlic in bunches, or by laying out on racks or on the floor. Some growers will power wash garlic post-harvest to reduce the amount of dirt on the wrappers before curing. This can result in cleaner wrappers and less handling post-curing. Most growers leave the tops intact while curing, though trimming the tops can speed curing and reduce handling post-curing. In areas with high humidity, circulating fans can be used to speed the curing process, while lower-humidity areas can have adequate curing in two to three weeks. After the leaves have dried and papers have shrunk to the bulb, the garlic can be trimmed and stored in clean boxes or mesh bags at 32-35°F and 65-75 percent relative humidity.
Heads can be graded for sale and seed selection. U.S. No. 1 garlic requires that bulbs be no less than 1.5” in diameter, but depending on your market, you can grade to further specifications. A simple grading tool can allow a grower to select bulbs for varying price points and seed selection.
Garlic can be a very rewarding and profitable crop for the commercial grower and home gardener. Through the use of proper production practices, growers can reach improved yields, year after year.
Collin Thompson is the Farm Manager of The North Farm at the Michigan State University Upper Peninsula Research and Extension Center in Chatham, Michigan and a Community Food System Educator with MSU Extension.
— Collin Thompson, Michigan State University Extension
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