Leeks, onions, and shallots are all of the lily family. The leek seeds are shield-shaped, with their backs protruding, the umbilicus slightly depressed, and the seed coats are numerous and fine. The onion and green onion seeds have a triangular conical shape with angular edges. Onion seed coat wrinkles less and neat, umbilical deep; large onion skin wrinkles and more irregular, umbilical shallow concave, slightly smaller than the onion seed. The life of Allium vegetable seeds is short. The newly harvested seeds should be used in production (80-85% of the seed germination rate in the year, 40-55% in the second year, and 10-15% in the third year). More than two years, the seeds basically lost their germination potential. The method for rapid determination of the germination potential is to hold 250 g of water in a metal cup. After the water is opened, put 20-30 seeds into the metal cup. After boiling for 18 minutes, the seeds can be directly observed. The full new seeds extend 1-3 mm long. Milky white radicles, individual seeds that are not full, can be squeezed out with a fingernail. If the radicle cannot be boiled and the white buds cannot be squeezed, it proves to be an old seed, which has lost its germination potential and cannot be used for planting. Multi Span Plastic Film Greenhouse Arch greenhouse is a kind of economical greenhouse, which is welcomed by the users with graceful curve form and low cost. It has beautiful appearance, fluent visual, reasonable structure and good performance for keep temperature. It is economical greenhouse because of its relatively low manufacturing cost. It can be applied in most areas of China. Double membrane greenhouse is used more in north of China, while single film greenhouse is used more in southern region. It can get maximum sunlight when visible light is within the scope of 0.4 to 0.7 microns and form a thick envelope, which can effectively prevent heat loss and prevent the invasion of cold air. Adopting a double membrane can greatly improve heat preservation performance of the greenhouse and save operating cost. The top cover material is polyethylene lifelong anti-fog and anti-dipping film po-covering. The outer of it has the function of UV protection and the inner has the function of preventing from the sets of dew. According to the needs of customers, the sides of the greenhouse can be covered with polyethylene lifelong anti-fog and anti-dripping po-covering or polycarbonate hollow plate. Multi Span Plastic Film Greenhouse,Pc Board Greenhouse,Pc Sheet Covering Greenhouse,Greenhouse Pc Board JIANGSU SKYPLAN GREENHOUSE TECHNOLOGY CO.,LTD , https://www.skyplantgreenhouse.com