(1) The germination period lasts for 7 ~ 10 days from sowing to the appearance of the first true leaf. The effective accumulated temperature above 7℃ is 140℃. In order to accelerate the germination and excavation of seeds, higher temperature and humidity conditions are needed in this period. The optimum temperature is about 20℃. Due to the low temperature in early spring, the emergence time is longer, generally 15 ~ 20 days. (2) The seedling stage is from the first true leaf unearthed to field planting. The seedling stage of spring sowing is generally 80 ~ 90 days; Autumn sowing seedlings can't be planted until the next summer, so the autumn sowing seedling period is as long as 8 ~ 9 months. Autumn sowing seedlings are divided into early seedling stage (about 40-50 days before winter). The border surface should be kept moist in production to facilitate the growth of seedlings. After winter, it is necessary to pour frozen water once during the period from light snow to heavy snow, so that the surface layer of soil is refined and the bottom layer is full of water, ensuring the safe overwintering of seedlings. In winter, the seedlings stop growing and enter a dormant period, about 90 ~ 100 days, and turn green in early spring of the following year. The length of the dormancy period varies from region to region. During this period, the outside climate is cold. In management, the soil surface should be often poured into the gaps in the field to keep warm and moisturize, so as to ensure safe wintering. It takes about 80 ~ 100 days from greening to planting. This period is the key period for cultivating strong seedlings. In production, the planting time is determined according to the seedling situation, and the management measures are promoted. (3) The formation period of Welsh onion is from planting to harvesting before winter, which generally takes 120 ~ 140 days. The plant grows slowly after survival, and after autumn cooling in the middle and late August, the green onion elongates and enters the rapid growth period. This period is a key period for yield formation, fertilizer and water management, intertillage and soil cultivation, and softening of green onions. If proper measures are taken, the scallion will be elongated and thickened rapidly, thus ensuring the quality and yield of the scallion. When the temperature drops to 4 ~ 5℃, the growth of leaves tends to stop, and the nutrients stored in leaves are transferred to green onions. After the frost, the growth of green onions stopped completely and the harvest season began. The optimum temperature for the growth of Chinese onion is 20 ~ 25℃, when the weight gain of leaves and whole plant is the fastest. 13 ~ 20℃ is the most suitable for the thickening, elongation and enrichment of Chinese onion. (4) Greening period: When the temperature reaches above 7℃ in the following spring, the plants begin to turn green until the buds are exposed from the leaf sheath, which is the greening period. This period mainly refers to the reproduction of green plants. In the turning green stage, the flower buds on the stem plate of Chinese onion will not differentiate into new leaves after differentiation. Therefore, attention should be paid to protecting the existing functional leaves, maintaining good photosynthesis, and manufacturing and accumulating nutrients for plants. The key points of management in this period are to speed up the development of existing functional leaves of Welsh onion, water green water in time, topdressing and raising seedling fertilizer, timely intertillage, weeding and ridging, promote root development, consolidate soil and raise intertillage temperature. The green turning period is about 30 ~ 40 days. (5) The bolting period is from the time when the bud at the top of the flower bud is exposed from the leaf sheath to the time when the flower bud grows and breaks. This period is usually 10 ~ 15 days, mainly for the development of flower organs. The flowers of Welsh onion are green and have strong photosynthetic capacity, and the photosynthetic intensity is four times higher than that of the same leaf. During the flowering and fruiting period of seed plants, 80% of the required assimilation products are made from flower buds, which has a great influence on seed yield. During this period, watering and fertilization should be controlled on the basis of topdressing green manure to avoid brittle flowers, rapid growth and easy folding and lodging in the wind. Controlling water and fertilizer can make flower buds thick, short and strong, and have strong wind resistance, which is beneficial to improve onion seed yield. (6) After the involucre (i.e. bulbous inflorescence) of the flower ball breaks, the florets open from the center to the periphery in turn, and the flowering period ends. The flowering period of a flower is 2 ~ 3 days, and the flowering period of a flower ball is about 15 days. According to this rule, the best time for artificial pollination or insect pollination can be arranged reasonably at flowering stage. The length of flowering period is related to variety, plant size and flowering temperature. The bigger the plant, the bigger the bulb, the more flowers and the longer the flowering period. When the temperature is high, the flowering process is fast and the flowering period is short. The suitable temperature for flowering period is 16 ~ 20℃. This period is the key moment to improve the seed yield of Chinese onion, so it is necessary to create conditions as much as possible to ensure full pollination and improve the seed setting rate and seed setting rate. Welsh onion is an insect-borne flower, which spreads pollen through the frequent activities of insects to achieve the purpose of pollination, fertilization and fruiting. In order to ensure the activities of beneficial insects, pesticides with high efficiency and low toxicity are generally not used or used less at flowering stage, which is beneficial to the normal activities and pollination of insects. You can also improve the seed setting rate by releasing bees or artificial pollination. In the season when green onions are in full bloom, not watering is beneficial to pollen spread. (7) The fruiting period is from flower withering to seed maturity. The florets in different positions in the same flower ball have different opening time, and the seed maturity time is also different. The temperature is low when flowering is early, and it takes 30 days from flowering to seed maturity; In the later stage, the temperature is high, and the seeds develop rapidly, which takes about 20 days, but the plumpness is poor. This period is the key period to increase the 1000-grain weight of Welsh onion seeds. Management focuses on protecting and prolonging the life of functional leaves, which can be watered with small water and injected with quick-acting potassium fertilizer nutrient solution. At this stage, it is not suitable to go into the field to avoid breaking leaves or flower buds. When the capsule with 1/3 at the top of the flower ball cracks to expose black seeds, it should be harvested in time. The seeds harvested too early are not full, and too many seeds fall with the wind when harvested too late, which reduces the yield.