Salix is a genus of around 300 species of normally deciduous trees and shrubs found in habitats ranging from lowland meadows and riverbanks to sand dunes and mountain screes worldwide except in Australia. They have simple, entire or toothed, usually alternate leaves and bear very small flowers in catkins, before or with foliage.
Many Salix species are very vigorous growers and are extremely tolerant of neglect. There are many Salix species suitable for bonsai. One of the most frequently used species is Salix babylonica and its many varieties that tend to have a weeping habit. Salix do not lend themselves to typical bonsai forms and are normally seen with thick trunks and graceful weeping branches.
BONSAI CULTIVATION NOTES
POSITION Full sun though protect from scorching Summer sun. Though frost hardy to at least -10°C, temperatures below -3°C can cause dieback of fine branches so some frost protection should be afforded.
WATERING Salix prefer plenty of moisture and should never be allowed to dry out. They are very thirsty plants and require regular watering, particularly during hot periods. It is often recommended that Willows are stood in a shallow tray of water during the Summer months; my personal feeling is that this is only recommended on very hot days where excess water will either evaporate or be taken up by the tree within a few hours.
FEEDING Every two weeks from Spring until late Summer.
REPOTTING Salix require repotting in Spring as buds extend. It is not necessary to repot twice in a season as has been stated in some bonsai text.
PRUNING Cut back very hard in late Winter, continually trim back shoots during the growing season. For Salix grown in a weeping form, branches are cut back nearly to the trunk each Winter and replaced by new branches (which need wiring downwards) each Spring.
PROPAGATION Salix are one of the easiest plants to propagate (other than S. caprea/ Pussy or Goat Willow); softwood or hardwood cuttings can be taken at any time. The thicker the cutting, the greater the success rate; cuttings 5" thick (or more) can be taken easily from hardwood in late Winter.
PESTS AND DISEASES Aphids, caterpillars, sawflies, willow scale and rust may be a problem.
STYLING Ideally styled in weeping or cascade forms in all sizes.