- Name also: Narrow Leaf Cattail, Narrow-leaved Cattail, Lesser Reedmace
- Family: Cattail Family – Typhaceae
- Growing form: Perennial herb. Rootstock horizontal, creeping.
- Height: 150–200 cm (60–80 in.). Stem unbranched, glabrous.
- Flower: Inflorescence compact, thin, cylindrical, 2-parted terminal spike. Flowers very small. Male flowers on upper part of inflorescence, female flowers below; flowers clearly separate. Female flowers cinnamon brown, 8–20 cm (3.2–8 in.) long, 1.5–2.5 cm (0.6–1 in.) thick. Tepals hairy and scaly. Stamens 1–8, stigmas thread-like. Pistils 1.
- Leaves: Alternate, stalkless, long-sheathed, mostly on bottom of stem. Blade often longer than inflorescence, 3–9 mm (0.12–0.35 in.) wide, linear, quite rigid, spongy, curled at tip, clear green.
- Fruit: Achene.
- Habitat: Shores, ditches, excavation sites. Quite deep in water.
- Flowering time: July–August.
Lesser bulrush is a delicate water plant which thrives between the water line and up to 1 metre deep. It never spreads onto dry land. It can most likely be found in a clay-grey lake or low-salt brackish water, growing on muddy shores in southern Finland. It is often quite local and doesn’t spread easily from one lake to another. This strange species has not really managed to exploit human activity. Lesser bulrush is clearly rarer than its big brother common bulrush (T. latifolia), and it grows further south and is more demanding. Useful identification markers are the habitat, the width of the leaves and the inflorescence. In controlled reservoirs and basins the species might cross with each other, in which case the hybrid is a sparsely-flowering bluish green plant (T. angustifolia x latifolia) that is larger than its parents and whose staminate and pistillate flowers are slightly different from each other.