American woody plant expert Dr. Michael Dirr states that the weeping willow (Salix babylonica) is "one of the best-loved and most hated trees in landscape history." Beautiful form, with weeping curtainlike branches that are magnificent along a lake or pond's shores, makes this deciduous tree loved. But it drops lots of leaf and twig litter, is short-lived and is well known for extending its roots anywhere water is available--including pipes, wells and drains. Grow this tree in U.S. Department of Agriculture winter hardiness zones 5 though 9.
Always situate a weeping willow where it will receive abundant sunshine--no less than 8 hours of direct sun rays daily. It grows alright in partially shaded spots, but too little sunlight causes irregularly shaped trees, scrawny limbs, potential infestations from aphids or mildew problems.
There is little doubt this tree species needs a moist to wet soil to look its best. A fertile soil will sustain the most robust growth as long as it is never too dry; even sandy soils work well (again, if water is abundant). Organic matter like mulch on the soil surface improves fertility of soil as well as retaining soil moisture in the heat of summer.
Plant the weeping willow in a naturally moist area of your property such as in a ditch or swale that collects rain runoff, or at the edge of a body of freshwater. This greatly diminishes the need for irrigation to keep the tree looking its most beautiful. It would be a poor decision to plant this tree where irrigation is always needed in order to keep the soil moist to wet. Soil can be slightly drier in winter when this deciduous plant is dormant.
Unless your garden's soil is sandy or generally infertile, no fertilization schedule is needed. Use of organic mulches over the root zone improves soil quality and increases the amount of nutrients available. Consider maintaining a mulch layer 3 to 4 inches thick over an area that starts several inches from the truck and extends 3 to 5 feet beyond the reach of the outermost branches.
Lots of leaf and twig litter drops from the weeping willow, and can muddy water in ponds or lakes over which its boughs reach. The roots will also take any opportunity to grow into areas underground where moisture is available. Therefore, never plant this tree species within 40 feet of underground drains, septic tanks or other water-carrying pipes or conduits on your property. Nothing will successfully grow under the canopy of the tree, including grass, so a blanket of mulch may be the best way to contain leaf and twig litter and make the tree look part of your overall garden scheme. Canker can inflict trees and lead to their early demise, making them look quite hideous as they decline from the ailment.