Acorus calamus ‘Variegatus’ is a handsome, sword-like plant with cream and green variegated leaves.
Butomus umbellatus has narrow, slightly twisted foliage with umbels of rose-pink flowers in the summer.
Caltha palustris ‘Flore Pleno’ is a native aquatic plant which has compact clumps of dark green leaves. Being native it is early, announcing spring with a profusion of double, bright yellow flowers.
Iris Laevigata, the asiatic water iris is a clump forming plant with tall, sword-like leaves. This variety has blue flowers during early and mid summer, but there are other colour-forms including white, purple and pink.