Picea pungens glauca, placed in the Pinaceae family, is commonly known as Colorado Blue Spruce and is widely cultivated as an ornamental tree. It is among the most widely planted ornamental spruces in gardens and parks. It is also grown for Christmas trees especially in North America. When growing from seed the degree of intensity of the silvery blue colour will vary between individual seedlings and a range of seedlings varying from grey green to bright glaucous blue is usual. A native tree to South-western N. America and the Rocky Mountains it is now cultivated in many parts of the temperate world. It cannot grow in the shade and must be grown in an acid soil. It withstands strong winds and mountain exposure very well but is not suitable for planting close to the coast. It also cannot tolerate atmospheric pollution.