This is an incredibly diverse genus, ranging from the annual bedding varieties to shrubs and trees. The conditions required also vary enormously, some species being happy in desert conditions, while others are marginal pond-dwellers. All, except the bedding varieties, are poisonous and have an irritant sap.
There are over 370 species growing worldwide in both temperate and tropical regions. The greatest proportion is found across North, Central and South America.
Most of the perennial border varieties require moist, fertile soils and will grow well as a bog or marginal plant. Either sun or part shade is acceptable.