Salix babylonica but beyond China, it has not generally been as successfully cultivated as some of its hybrid derivatives, being sensitive to late-spring frosts. In the more humid climates of much of Europe and eastern North America, it is susceptible to a canker disease, willow anthracnose ("Marssonina salicicola"), which makes infected trees very short-lived and unsightly. "Salix babylonica" (Babylon willow) has many cultivars, including: Various cultivars of "Salix matsudana" (Chinese willow) are now often included within "Salix babylonica", treated more broadly, including: Yet other weeping willow cultivars are derived from interspecific "Salix" hybrids, including "S. babylonica" in their parentage. The most widely
Salix fragilis also spreads by root suckers, expanding into pure 'groves'. "Salix fragilis" is cultivated as a fast-growing ornamental tree. The cultivar "Salix fragilis" 'Russelliana' (syn. "S. fragilis" var. "russelliana" (Sm.) Koch) is by far the most common clone of crack willow in Great Britain and Ireland, very easily propagated by cuttings. It is a vigorous tree commonly reaching tall, with leaves up to 15 cm long. It is a female clone. "S. fragilis" has escaped cultivation to become an invasive species in various parts of the world, including: New Zealand; the upper half of the United States; and South Africa. In