Too much, or too little water. The symptoms are similar.
Dig down and check the soil a few inches deep. It should be moist, not dry and not damp.
Willows fall in the Genus called Salix spp. Family: Salicaceae.
Salix cordata was created in 1803.
Salix atrocinerea was created in 1804.
Salix bebbiana was created in 1895.
Salix Säydäş died in 1954.
Salix geyeriana was created in 1858.
Salix gooddingii was created in 1905.
Salix Säydäş was born in 1900.
Salix is Latin for "willow." The weeping willow is not a true species in its own right, but a hybrid of the white willow Salix Alba and the Chinese willow Salix babylonica.
Salix OS was created on 2009-09-16.
The scientific name for the weeping willow tree is Salix.Bear in mind that there are over 400 different species of salix, which also have their own specific scientific subname.
The scientific name for American pussywillow is Salix discolor.