The supple branches of the weeping willow (Salix babylonica) sweep gracefully from its open crown to the ground. It grows quickly, needs moist soil and is well-suited for locations near water. It thrives in U.S. Department of Agriculture zones 5 through 10. The weeping willow should be planted in full sun with generous growing space because it reaches from 40 to 50 feet tall and 30 to 40 feet wide. Weeping willows need regular fertilization with a balanced, all-purpose fertilizer. If the soil is extremely poor or compacted or the tree shows signs of distress, it may benefit from deep root fertilization.
Attach the root feeder, which usually resembles a hollow spike about 1 or 2 feet long, to the end of your garden hose. Attach the hose to a water faucet. You can buy a root feeder for home use at nurseries or home improvement centers. Each root feeder system is different, so follow the directions for your particular system. For example, one system uses a bucket instead of a garden hose for the water source.
Fill the root feeder compartment with a balanced fertilizer such as 10-10-10 or 20-20-20. Again, follow directions for your specific root feeder. Some root feeder makers also offer their own fertilizer designed for their feeders. Apply the amount of fertilizer recommended by the manufacturer on the fertilizer package for your size weeping willow. If in doubt, consult a professional nursery tree expert for fertilizer amounts.
Insert the pointed end of the root feeder stake into the soil at a spot just at the drip line of the tree. The drip line is the outer edge of the tree’s canopy, at the end of the area where water drips from the tree when it rains. If the branches are long enough, the weeping willow’s drip line is defined by the place where the outer branches touch the ground. Read the directions for your specific root feeder regarding how far to push the spike into the ground. In general, you insert a root feeder into the soil up to the point where it connects to the hose or the bucket.
Turn on the water faucet or fill the bucket with water, according to your particular root feeder. This injects water and fertilizer into the ground to feed the deep roots. Leave the water on and the feeder inserted for about one minute. If water pools to the surface, turn off the water and remove the feeder.
Turn off the water and move the feeder to another spot on the drip line about 1 1/2 to 2 feet away from the first insertion point. Repeat the deep root feeding for the weeping willow. Continue this process all the way around the drip line.
Repeat the root feeding annually in the spring after the last frost or in the autumn after the leaves fall. Feed two to three times a year if the tree needs additional nutrients. Signs for nutrient deficiency include slow tree growth, yellow or faded leaf color, small leaves or early leaf drop.