Buphthalmum Requires even moisture; the soil should be allowed to dry out partially between waterings to prevent root rot. The most common species in cultivation. It is a compact, clump-forming perennial that typically grows 18 to 24 inches tall and features willow-like, dark green leaves. buphthalmum A species specific to the island of Sardinia. Growing & Care Instructions Requires even moisture; the soil should be allowed