Arumleaf arrowhead is a perennial aquatic herb that is known botanically as sagittaria cuneata. It grows up from an underground rhizome and propagates itself by spreading rhizomes. Found in the shallows of freshwater ponds, pools, lakes, marshes and stream beds, arumleaf arrowhead is named for the pointed-heart shape of its leaves and produces small white flowers in the summer from June through August. It requires little pruning save removal of damaged or dead foliage.
Prune away any dying, damaged or diseased foliage whenever you come across them throughout the growing season. Perform a regular inspection of the plant every month or so to look for problem areas. Use secateurs to cut the damaged stems back all the way down to the crown of the plant. Lift each stem out of the water, and discard in the compost bin or trash.
Prune away the arumleaf foliage in the fall after the first hard frost in climates where the top growth does not overwinter. This can also be done in the early spring in time to make way for new growth but you run some risk of disease setting in from rotting foliage by doing so. Cut down all of the dying or dead foliage and stems to the crown of the plant and discard. Placing your cuts under the waterline will give a tidier appearance, but leaving some stem above the waterline will not harm the plant.
Hard prune your arumleaf arrowhead once every 2 to 3 years to rejuvenate the plant, restore a pleasing shape and control its size. Shear off up to one-third of the plant's top growth each year by cutting down to the crown. Pause between each cut, and observe the plant to make sure each cut adds to the pleasing appearance and natural symmetry of the arrowhead.