The growth and development process of watermelon can be divided into germination stage, seedling stage, vine stretching stage and fruiting stage. Like other crops, watermelon has two stages: vegetative growth and reproductive growth. 1, germination period? Seeds germinate until cotyledons are flattened, and 2-3 young leaves are formed at seedling tips. At 25-30℃, it takes about 10 days. At this stage, depending on the nutrients stored in seeds, the dry weight of aboveground parts increased little, and the root system grew faster. 2. Seedling stage? It usually takes about 20 days from the first true leaf to the "clumping stage" of 5-6 leaves at 20-25℃, while it takes about 30 days at 15-20℃, which can be divided into two-leaf stage and bush growth stage. In the two-leaf stage, the growth of hypocotyls and cotyledons gradually stopped, the main stem became shorter, and the seedling tip had 4-5 young leaves and 2-3 Yuan Ye basal parts, so the plant grew slowly at this stage. The clumping stage refers to the stage when two leaves spread to 5-6 leaves, and the seedling tip has 8-9 tender leaves and 2-3 Yuan Ye basal parts. This stage is the growth of leaves and stems. The dry weight, fresh weight and leaf area of shoot increased slightly at seedling stage, but the growth rate increased exponentially. The root system grew faster. The lateral branches and flower buds are well differentiated. Lay a good foundation for the growth, flowering and fruiting of stems and leaves in the future. 3. Stretching period? The seedlings are clustered, and the female flowers bloom at the fruit-setting festival. At the temperature of 20-25℃, it takes about 20-25 days. With the elongation of internodes, the dry weight of plants increased rapidly. The vine-stretching period is the main period of stem and leaf growth, with the aim of establishing a strong vegetative body. At this stage, the growth center is the growth point, and there is no nutrient transformation between the main vine and the lateral vine. 4. Result period? The female flowers on the fruit-setting festival bloom until the fruit is ripe and the whole plot is harvested. It takes about 4-5 days for the second and third female flowers of the main vine to blossom and set fruit at 26℃. This is the turning point from vegetative growth to reproductive growth. The growth amount and speed of stems and leaves are still relatively strong, and the growth of fruits has just begun. With the expansion of fruit, the growth of stem and leaf gradually weakens, and fruit is the growth center of the whole plant. The fruit growth period is generally 30-40 days, and it will take longer if the fruit is picked for the second time. From seedling to flowering and fruiting, it is a vegetative growth stage, mainly with long roots, vines and leaves, which lays a good foundation for fruiting. It is characterized by slow initial growth, vigorous growth after vine pulling, strong branching and large growth. At the same time, it begins to blossom and bear fruit, and the reproductive growth stage from flowering to fruit maturity is mainly melon and fruit expansion. Its characteristic is that the melon vines can still grow at the initial stage of fruiting, and then the watermelon fruit grows gradually, and the melon vines stop growing, and all nutrients are used for fruit expansion. However, if there is too much fertilizer and water before the vegetative growth period, it will cause melon vines to grow long and it is difficult to drop flowers and fruits. After the watermelon bears fruit, even if it is full of fat and water, it will not grow in vain, and it can also promote the watermelon to grow bigger and have better quality. Therefore, it is very important to coordinate the contradiction between vegetative growth and reproductive growth and adjust the relationship between growth and fruit through cultivation measures to win high quality and high yield of watermelon. 2. Requirements of watermelon on environmental conditions: 1. Temperature 2. Sunshine 3. Moisture 4. Soil.