Willow trees primarily grow in moist environments and are commonly found near bodies of water. Their natural habitats include wet or low-lying areas such as floodplains, fens, streamsides, riverbanks, gravel bars, swamps, and ditches. They thrive in soil that is consistently moist, which is why they are often seen along rivers, lakes, and wetlands

. Geographically, willows are distributed widely across the Northern Hemisphere, including North America, Europe, and Asia. In North America, they are found throughout the United States and Canada, especially in the Pacific Northwest, the Great Lakes region, and along the Mississippi River. In Europe, they grow in countries like the United Kingdom, France, Germany, and Scandinavia. In Asia, they are prevalent in China, Japan, and Russia. Willow trees are also present in the Southern Hemisphere in countries such as Australia, New Zealand, and South Africa

. Some willow species, like the prairie willow, prefer drier upland areas such as hill prairies or open woods, but most willows favor wet habitats. Additionally, willows are often planted in urban environments for landscaping, especially in parks and gardens where moist soil conditions can be maintained

. In summary, willow trees grow best in moist, wetland environments near water sources across many parts of the world, including North America, Europe, Asia, and parts of the Southern Hemisphere