Green arrow arum, known botanically as peltandra virginica, is an aquatic perennial herb that grows in collections of shallow, fresh water. It flowers in May through July and develops green, bunched fruit that resembles a cluster of capers following bloom. Stems called spathes grow up through the water directly from an underground rhizome. Green arrow arum rarely requires pruning, save for the removal of damaged or diseased leaves to control size or to prevent reseeding.
Prune away any damaged or diseased foliage throughout the growing seasons as you come across them. Use clean, sharp secateurs to cut down the stems to the soil or just below the water line to maintain a clean and tidy appearance.
Cut off mature fruits in the fall or very early winter to prevent seeds from developing, anchoring in the soil, germinating, rooting and producing new plants. Use secateurs to cut away the fruit head from the spathe or cut down the entire spathe stem to the soil line.
Hard prune your green arrow arum once every few years or as needed to control the size and shape of the plant. Hard prune in the spring or in the early fall to reduce heat and cold stress on the plant and minimally disrupt bloom and fruiting.