Question of the Week
Answer: Cultivated garlic, Allium sativum, is a member of the lily family. It can be divided into two subspecies: Allium ophioscorodon (bolting or hard-neck cultivars) and Allium sativum (non-bolting or soft-neck cultivars). Allium ophioscorodon produces elongated flower stalks, often referred to as scapes, and flower-like bulbils at the top of the stalk. Soft-neck garlic does not produce bulbils except in times of stress. While both bulbils and individual cloves can be propagated vegetatively, bulbils take longer—up to two seasons—to produce mature bulbs, and require special care because the young plants are very small and fragile.
As with all crops, soil fertility management is essential for garlic production. It is a good idea to get a soil test before you begin field preparation. Request recommendations for nutrient requirements for onions when you send a soil sample to a soil-testing laboratory. To find a laboratory, consult ATTRA's searchable Alternative Soil Testing Laboratories database. For additional information on organic fertility management in vegetable crops, see the ATTRA publication Sustainable Soil Management.
Since garlic is a high-value crop and a heavy feeder, it deserves your best ground. It needs full sun and a full range of available nutrients. A pH of 6.8 to 7.2 is ideal; many nutrients are tied up in soils that are more alkaline or more acidic than this. Garlic will grow in almost any well-drained, friable (easily crumbled in the hand) soil, preferably with high organic matter content. High organic matter aids in soil water-holding capacity and drainage. If possible, begin soil preparation the year before planting. In his book Growing Great Garlic, Ron Engeland recommends building up the soil over a period of one to two years using animal and green manures before the garlic is planted. See the ATTRA publication Overview of Cover Crops and Green Manures for information on building soils with cover crops.
Provide additional nitrogen, if needed, through supplemental use of organic fertilizers. Nitrogen can be applied in the fall at planting if a slow-release fertilizer such as soybean meal is used. Avoid applying any form of soluble nitrogen fertilizer in the fall to prevent contamination of ground water as well as loss of nitrogen to leaching. Do not apply nitrogen when the bulbs are beginning to enlarge, since it will encourage excessive leaf growth and reduce bulb size. Another way to add fertility is to sidedress with compost after leaf emergence in the fall, then apply fertilizer again in the spring. Avoid fertilizing beyond May, since high nitrogen levels at this stage may actually decrease bulb size. Some organic growers apply foliar sprays of liquid fish and seaweed fertilizer, several times in the spring.
If foliar feeding is used to supply nutrients, it should be done prior to the 4th or 5th leaf stage. A good surfactant (or spreadersticker) is essential to hold the solution on the garlic's waxy leaves. There are a limited number of spreader-stickers that are approved by the USDA National Organic Program. If you are certified organic, see the OMRI list of approved products or check with your certification agency to ensure that you are using an allowed product.
The ATTRA publication Garlic: Organic Production provides much more useful information. It addresses most aspects of organic garlic production, including seed sources, organic fertility management, pest management and harvesting and storage. Marketing and economic considerations, including enterprise budgets for organic garlic production, are also discussed.
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