P. Aquatic or water plants suitable for growing in shallow pools or. The tuberous should be placed in a piece of sacking or old basket, filled with rich loam and well rotted manure and dropped into the water. The white appear in July, but the most striking feature of these plants is the arrow-shaped foliage. Sagittaria sagittifolia is a native British plant to about 2 ft. The double-flowered form is most attractive. Increase by division in May.