Introduction to the Characteristics of the American Flag Leek Variety

Leek, also known as sea garlic, foreign garlic sprouts, and flat-leaf onion, belongs to the genus Allium in the Liliaceae family and is a biennial herbaceous plant. It originated in south-central Europe and was introduced to China at the end of the 19th century. Since its leaves, pseudostems, and flower stalks are all edible and it is rich in carbohydrates, it is mostly used as a substitute for garlic sprouts or for dehydration processing and export, with very significant economic benefits. In 1992, our institute introduced the "American Flag Leek" from abroad, and over 8 years it has been successively promoted in Fujian, Guangxi, Guizhou, Sichuan, Shanghai, Zhejiang, Hubei, Hunan, and Shaanxi, with a cumulative promotion area reaching 6500 hm2, and it is very popular among vegetable farmers and consumers. Its characteristics and key cultivation techniques are introduced as follows.

I. Characteristics

It has strong growth vigor, with a plant height of about 70 cm. The pseudostem is as white as that of scallion, and the leaf blade is flat like that of garlic. The leaves are long lanceolate, alternate, with a waxy bloom on the outside, 2.5-5 cm wide and 30-50 cm long. The round leaf sheaths wrap around each other to form the pseudostem, and the outer skin is membranous and white. The flower stalk is solid, round in cross-section, 1 cm thick at the base, and 80 cm long. It rarely suffers from pests and diseases, is cold-tolerant, and has wide adaptability. It can endure a high temperature of 38°C and a low temperature of -10°C. The suitable daytime temperature for growth is 18-22°C, and the nighttime temperature is 12-13°C. Its root system is relatively shallow, and it is neither drought-tolerant nor waterlogging-tolerant, so irrigation and drainage must be carried out promptly in production. Leek belongs to the green plant vernalization type. The transition from vegetative growth to reproductive growth requires that at the seedling stage with 4-5 leaves, it undergo flower bud differentiation after a relatively long period of low temperature at 5-8°C, and then, upon encountering long daylight, it bolts flower stalks at 18-20°C. The flower stalk is an umbel inflorescence with an involucre outside. When flowering, the involucre splits open on one side and falls off. There are 800-3000 florets, light purple or pink, clustered in a ball, bright and beautiful. The seeds are angular, black, with a 1000-seed weight of about 2.8 g. After sowing, it can be harvested continuously for 7-8 years (the harvest situation is the same as that of chives), and 667 m2 can annually produce 6500-8000 kg of tender shoots and flower stalks.

II. Key Cultivation Techniques

1. Sowing at the appropriate time. For production aimed at harvesting one-year-old mature plants, in northern regions seedlings are generally raised in mid-March, transplanted in early to mid-June, and harvested in late October. Before raising seedlings, prepare the land and apply base fertilizer, and make seedling beds 6-8 m long and 1-1.5 m wide. To plant 667 m2 of leek, 100-130 m2 of seedling bed is needed. Water the bed surface thoroughly, and after the water infiltrates, evenly broadcast the seeds and cover with 1 cm of soil. For production aimed at harvesting tender shoots, sowing can be done in late spring and early summer, and the tender shoots can be harvested and marketed in the same year.

2. Cultivate strong seedlings. After sowing, keep the surface soil moist frequently to facilitate emergence. After the seedlings emerge completely, spread a layer of sifted fine soil on the bed surface to preserve moisture and promote rooting. In case of drought, irrigation can be applied to keep the bed surface alternately dry and wet, and weeds should be removed promptly. When the seedlings have 3-4 leaves, in combination with irrigation, apply 10 kg of ammonium sulfate per 667 m2 to promote rapid growth. If the seedlings are dense, thin them promptly. If a tendency toward spindly growth is found, control irrigation. Irrigate once 1-2 days before transplanting to facilitate lifting the seedlings.

3. Reasonable close planting. Clear away residual plants and weeds from the previous crop, level the land, and broadcast 5000-7000 kg of farmyard manure per 667 m2, apply it deeply and harrow finely so that manure and soil are mixed evenly, and make beds 20 cm wide with 20 cm between beds. On each bed, plant 3 rows with a row spacing of 7 cm and a plant spacing of 7 cm. Each m2 can hold 126 seedlings, and 667 m2 can hold 84000 seedlings. The transplanting depth should be such that the heart leaf is not buried, and irrigation should be applied immediately after transplanting. Because of the high density of this transplanting method, individual plants are relatively small, and yield increase relies on the population.

4. Management after transplanting. When the heart leaf begins to grow, irrigate once, and when the surface soil is suitably dry and wet, loosen the soil to promote root growth. In July and August, the temperature is relatively high and rainfall is heavy. In addition to maintaining alternate dryness and wetness, drainage should also be carried out promptly after rain to prevent waterlogging. After September, climatic conditions are suitable and growth becomes rapid and vigorous, so irrigation and topdressing should be carried out promptly, and the soil should be kept moist frequently. Topdressing should be combined with irrigation. Entering the vigorous growth period, apply 10 kg of urea per 667 m2, and after half a month apply another 10 kg of urea. Also earth up twice to soften the pseudostem and improve yield and quality.

5. Production cultivation of flower stalks. The flower stalks of leek are very similar to garlic sprouts. Apart from being slightly less pungent and having a smaller involucre, their morphology and nutritional composition are not greatly different from garlic sprouts, and they can be marketed as garlic sprouts.

For those specifically producing flower stalks, in areas where they can overwinter safely in the open field, autumn sowing can be adopted, using bed cultivation with the same density as garlic cultivation, and winter irrigation should be applied in winter to ensure safe overwintering. After sprouting and growing in spring, because they have already passed the vernalization stage, upon encountering high temperature and long daylight in May, they will bolt quickly. When the flower stalks have grown to a certain extent and quality and yield reach the optimum, cut them close to the ground, strip off the leaves and leaf sheaths, and they can be tied in bundles for market. Their yield is higher than that of garlic sprouts. This production method has lower cost and higher benefit.