Green seedlings are most commonly used in urban landscaping, such as urban greening, residential areas greening, road greening, barren hills greening, river embankment greening, etc.. According to modern people's understanding, gardens are not only used for recreation, but also have the function of protecting and improving environment. Plants can absorb carbon dioxide, release oxygen, purify the air; can absorb the harmful gas and dust, to a certain extent reduce pollution; temperature and humidity can adjust the air, improve the micro climate; and reducing noise and wind, fire protection etc.. What is particularly important is the psychological and spiritual benefits of gardening. The city with the highest ranking of national happiness has no garden city. Recreation in scenic and quiet gardens helps to relieve the tension and fatigue of long hours, and restores mental and physical strength.