Japanese Weeping Willow Care Guide
Salix is a genus of deciduous willows native to cold, moist regions of the Northern Hemisphere. There are roughly 400 species in this group; one of the most commonly used for bonsai is Salix babylonica. Even though this is referred to as a "Japanese" willow, it actually originated in China, but has been extensively cultivated in Japan for thousands of years. If grown in its natural conditions, this beautiful specimen may reach upwards of 40 feet tall.
The foliage is made up of long, narrow leaves that are a yellowish-green on top and a paler green underneath, up to 3-6" in length and 3/8-1/2" wide. The Weeping Willow blooms manifest as upright catkins – fuzzy white puffs about one inch in size that are preceded by striking golden anthers.
The twigs are rope-like, characterized by their drooping nature, reaching down from the branches toward the ground. The bark is brown-gray and furrowed, making it visually interesting as a bonsai subject.
Japanese Weeping Willow does best as an outdoor bonsai. If brought inside it should only remain there for brief periods. This species needs a period of dormancy, and root protection in extreme cold. An unheated garage or cold frame works well, just be sure to insulate the roots. When outside this tree loves full sun. It should only be placed in shade during extremely hot, dry spells.
Salix is fairly drought-tolerant, but should not be permitted to dry out completely. It thrives in cool, moist conditions (as evidenced by its native environments near water sources like ponds, lakes, and streams) and as such prefers a consistent watering routine. Like most bonsai, however, it will be prone to root rot if overwatered so do not allow it to sit in water. A humidity tray is a welcome accessory for this tree.
If the tree is to spend its winters indoors in a heated environment, you may place it in a shallow tray of gravel and water; this will help it recoup the rapid water loss from the dryer conditions.
Unlike the majority of its bonsai brethren, Salix is not a big fan of fertilizer. Administer an organic formula sparingly every couple of months during the growing season. Alternatively, we recommend a low-nitrogen feed applied every two weeks throughout the growing season. Regardless of the method you choose, make sure to fertilize away from the trunk and leaves to avoid burning the roots and foliage.
The Japanese Weeping Willow should be permitted to assume its natural, free-flowing form. It can, however, be guided through some shaping and wiring.
This species is a vigorous grower so frequent foliage pinching is required. Trim new growth weekly during the growing season, and at the end of winter do an aggressive trimming, paring the tree down to one third of what it started with.
Wiring may be done but it should not be aggressive due to the brittle nature of the branches. If you choose to wire, do so at the end of winter and try to follow the natural downward tendency of the branches, wiring loosely and checking often for cut-in.
Salix is one of the easiest bonsai trees to propagate. They are vigorous rooters and softwood cuttings planted in a moist, loose soil will result in roots setting very quickly and easily. In fact this species propagates so easily that hardwood cuttings of 4 or 5 inches in diameter taken in late winter can readily set root.
The best time to repot is in early spring, while the weather is still fairly cool. Willow needs repotting every year at a minimum – sometimes more – because the roots are enthusiastic growers. Prune the roots moderately and transplant into very well-draining, loose bonsai soil.
Insects/Pests & Diseases
Japanese Willow can be vulnerable to scale, aphids, and other seasonal pests. Scale are recognizable by their signature brown or blackish protective shells. This is the coating that houses the eggs. Remove the pests manually with the tip of a sharp knife, then make sure that all remaining residue is wiped or washed away, or treated with insecticide. If the eggs are allowed to remain, they will continue the lifecycle of these nuisances.
Aphids are tiny, light green, pear-shaped bugs that gather in groups on foliage. They are not fatal to the plant but the "honeydew" that their eating produces can contribute to other problems like fungus. These pests can usually be washed off in a gentle water jet, or you can treat them with a mild spray of dish soap and water.
Rust can affect your bonsai as well. This is a fungal infection that causes rust-colored spots, usually on foliage. Remove affected leaves and watch that moisture does not stay on the foliage, as this feeds fungal infections.