Alder trees are commonly found in moist areas near water. They are adaptable to drier areas but prefer moist soils. Alder's aren't commonly used in home landscaping but they are excellent trees for shade and screening. Alder trees are often used in reforestation projects to help sustain soil in wet areas. The most common Alder trees - the Red and White - grow 40 to 80 feet tall. Buy Alder tree seeds in 25, 50, 100, 500 and 1,000 seed packets.