If unpaved drainage ditches and collection ponds were more common locally, sweet flag, Acorus gramineus, might be also. It can provide a nicely neat border for such waterways, where the ground is too steep and damp for mowing. It can migrate into muddy situations and even into shallow water. Its dense network of fibrosus rhizomes helps to retain mud.

‘Variegatus’, with elegantly elongated and variegated leaves, is the most popular cultivar locally. It is rare in nurseries, but occasionally shared by friends and neighbors who grow it. Propagation by division is very easy. Single shoots or clumps of shoots grow if merely plugged into damp soil or mud. ‘Pusillus’ lacks variegation, and develops stouter leaves.

Sweet flag aggressively excludes other herbaceous vegetation, but does not migrate too rapidly. Plucking shoots and plugging them elsewhere accelerates migration. The dense foliage might get a foot deep. Individual leaves are very narrow, like grass. The mundane bloom is easy to ignore and is uncommon where the soil is not often saturated or muddy.