Causes of Secondary Growth in Garlic and How to Prevent and Control It

Garlic is one of the indispensable vegetables in people's daily lives, and it is also a popular vegetable that can be supplied year-round on the market. However, in recent years, due to improper planting methods, management practices, and other factors, a large amount of secondary growth in garlic has appeared, commonly known as "horsetail garlic" or "bread garlic," which makes the garlic unsuitable both for seed saving and for eating, severely reducing its marketability and economic benefits. What exactly causes secondary growth in garlic, and how should it be prevented and controlled? Based on observations and experiments in recent years, the author has summarized some experience for reference only.

I. Causes of Secondary Growth in Garlic

1. Improper selection of seed garlic. Since heredity is the main factor causing secondary growth in garlic, the first step in planting garlic should be to select garlic varieties suitable for local cultivation. Seed garlic should have large bulbs, plump cloves, and each clove should be clearly separated, with 4-8 cloves forming one bulb. If varieties unsuitable for local cultivation are selected, the occurrence of secondary growth in garlic will be greatly promoted.

2. Improper environmental conditions of the garlic seed storage site. If seed garlic is stored for 30 days before sowing at 14-16°C or 0-5°C with an relative air humidity of 75-100%, low temperature combined with high humidity will increase the rate of outer-layer and inner-layer secondary growth plants in garlic.

3. Improper sowing time. Garlic cloves are formed by the development of lateral buds in the leaf axils on the stem disc, and are simultaneously affected by temperature, light, nutrients, and many other factors. Therefore, blindly advancing the sowing time is also a main cause of secondary growth in garlic.

4. Improper treatment of seed garlic. In some places, garlic farmers like to chill or low-temperature treat the seed garlic before sowing, and then sow it, believing that this will make the garlic sprout earlier. In fact, doing so will also promote inner-layer and outer-layer secondary growth in garlic.

5. Improper selection of clove size. Some people believe that the larger the garlic clove used as seed, the better, as it is easier to grow. In fact, according to the author's observations over several years, the size of garlic cloves used as seed garlic must be within a certain range. If too small, they easily form single-clove garlic; if too large, more secondary growth will occur.

6. Improper cultivation and management measures. Garlic has strong adaptability, but during growth it is very sensitive to environmental conditions, nutrients, and water. Excessive fertilizer and water and partial application of nitrogen fertilizer during management will all cause secondary growth in garlic.

II. Prevention and Control Measures for Secondary Growth in Garlic

1. Select high-quality garlic as seed. As the farming proverb says, "Good seed produces good seedlings, and good seedlings produce high yields." Therefore, when planting garlic, the first step is to determine the selection of seed garlic. Garlic cloves with white color, plump terminal buds, and no disease or damage should be selected, and cloves with broken sprouts or rot must be resolutely discarded.

2. Improve storage conditions. Store seed garlic 30 days before sowing at a temperature above 20°C with an relative air humidity of 75%, which can very effectively control the occurrence of secondary growth.

3. Strictly follow the sowing period. The suitable temperature for garlic bulb expansion is 20-25°C. Above 26°C, garlic enters dormancy. Although new leaves can continue to differentiate when the sunshine duration is less than 13 hours, lateral buds on the stem disc cannot form. Therefore, when planting garlic, the sowing period must be strictly followed according to location and variety, and sowing cannot be blindly advanced. Garlic farmers often say, "Not at home during Mid-Autumn, not in the field during Dragon Boat" and "Spring garlic does not go beyond the ninth," which very clearly points out that autumn garlic is suitable for sowing from late September to early October, and spring garlic before mid-March.

4. Properly treat seed garlic. Before sowing, dry the seed garlic in the sun for 2-3 days to loosen the cloves and make them easy to separate. When sowing, peel off the garlic skin and remove the residual stem disc. This can not only reduce the occurrence of secondary growth in garlic, but also promote early sprouting and neat emergence of seedlings.

5. Reasonable close planting. Reasonable close planting is beneficial to the uniformity and individual growth of garlic. The optimal row spacing and plant spacing for white-skin garlic is 16 cm × 10 cm, and the optimal row spacing and plant spacing for red-skin garlic is 10 cm × 8 cm.

6. Strengthen management measures. Throughout the entire growth period of garlic, fertilizer and water supply need to be strengthened, but excessive fertilizer and water are not suitable. During the most critical bulb expansion period, 25-30 kg of garlic-specific compound fertilizer can be applied per mu as a top dressing; water lightly once every 3-5 days, keeping the soil surface from drying out; during this period, 600-fold potassium dihydrogen phosphate can also be sprayed on the leaves 2-3 times to supplement phosphorus and potassium fertilizer.