The weeping willow is a very popular ornamental tree that is often planted in large gardens and yards to provide both beauty and shade. Many people assume that the weeping willow needs to be planted near water, and although the tree is water-loving and should be planted in a wet climate, there is some flexibility in location. The root system of the willow is fast-growing and often surprising to those without experience in willow growth.
The crown of the weeping willow, when fully grown, can spread as much as 35 to 40 feet across. The root system, however, will grow at least this far, and will extend as deeply into the ground as the willow rises up. For a growing willow, the gardener can assume the roots go beyond the shade of the willow tree itself, and possibly into surrounding flower beds or lawns.
Because the weeping willow tree loves water, it will often grow in the direction of any water in the soil. This means that willow trees can be planted as far as 40 feet away from streams or ponds, and the roots of the tree will automatically seek out the water-rich soil. By gauging the length and location of nearby water sources, a grower can often tell how, and in which direction, the willow roots will grow.
When first planted, the weeping willow sapling should be placed over a bed of fertilizer, spread across the ground, mixed in with the soil, and then covered up by a blanketing layer of rich soil. This fertilizer will eventually seep up to the roots and give them important nutrients when the willow tree reaches a certain depth. At the top of the soil, a layer of mulch should be spread around the tree trunk.
Willows can grow very quickly when planted in the right conditions, around several feet per year if the soil is rich. If other willows are present, they can enter into an underground competition for soil and water sources. If too close, their roots can entangle and threaten the growth of both trees. For this reason, willow trees should be planted no closer than 40 feet away from each other.
Weeping willows often have problems growing in small gardens, often because their root systems are too persistent. If there are any sewer lines, irrigation lines, water lines, or underground sprinkler systems or pumps within a 40 foot radius, the willow can sometimes grow into them and ruin them with its roots, especially if any of the systems have developed cracks and are leaking water into the soil.