Button bush (Cephalanthus occidentalis)

Zones: Five to 10.
Exposure: Full sun.
Height: 1.8 to 6.1 m (6 to 20 ft).
Planting depth: Moist soil and will tolerate standing water up to 152 mm (6 in.). Button bushes are a temperate North American native shrub with dense, rounded heads (up to 25 mm [1 in.] across) comprising small, fragrant, tubular, funnel-shaped, white-to-cream flowers with red veined and mid-ribbed green leaves.
Dwarf water bamboo
Zones: Six to 10.

Exposure: Full sun to part shade.
Height: Up to 457 mm (18 in.).
Planting depth: Moist soil and will tolerate up to 102 mm (4 in.) of standing water. Although not a true bamboo, the upright green leaves and stocks resemble their namesakes and form non-invasive, dense clumps. A heavy feeder, this plant is best to fertilize regularly.
Rush plants
These plants fulfil an important function in the shoreline area to a water depth of approximately 508 mm (20 in.). Not only do they consume nutrients that are released by sinking biomasses (e.g. leaves, seeds, flower petals, pollen, etc.), they also take care of the air-gas exchange when the pond is frozen during the winter. Through the dry stalks, gases like methane escape, allowing oxygen to enter the pond. Tall plants like reeds, rushes, bur-reeds, also serve as sight protection for the waterway. Here are some specimens:
Cotton grass (Eriophorum)

Zones: Four to seven.
Exposure: Full sun to part shade.
Height: Creeping 152 to 205 mm (6 to 12 in.).
Planting depth: Moist soil and will tolerate up to 25 mm (1 in.) of standing water. This is a lush green grass-like plant that produces downy tufts of bright white seed heads in the summer.
Mare’s tail (Hippuris)
Zones: Four to 10.
Exposure: Full sun.
Height: 152 to 305 mm (6 to 12 in.).
Planting depth: Moist soil to submerged conditions. These aquatic plants resemble horsetails superficially, but are not hollow and produce small flowers.
Gold strike reed
Zones: Three to 11.
Exposure: Full sun to part shade.
Height: 305 to 610 mm (12 to 24 in.).
Planting depth: Moist soil and will tolerate being submerged up to 76 mm (3 in.). This variegated cultivar is a natural addition to most NSPs.
Corkscrew rush (J. effusus, J. filiformis, and J. inflexus)
Zones: Four to nine.
Exposure: Full sun to part shade.
Height: Up to 457 mm (18 in.) (creeping), while J. effusus ‘Unicorn’ are more upright and can reach heights of 610 mm (24 in.).
Planting depth: Moist soil and will tolerate being submerged up to 152 mm (6 in.) during the warm summer months. During mid-summer, the long spiral stems will begin to develop abundant seed heads, roughly 25 mm (1 in.) from the growing tip. This adds to the already cryptic nature of the plant’s form, as well, when submerged, these seed heads often form new miniature replicas of the mother plants. No NSP or water feature is complete without some form of Corkscrew rush and, with the many varieties available, there are plenty to select from.
Cardinal flower (Lobelia cardinalis)

Zones: Five to nine.
Exposure: Full sun to part shade.
Height: 610 to 1219 mm (24 to 48 in.).
Planting depth: Moist soil. Cardinal flowers were first discovered in Canada in the 1600s by French explorers. During the summer, Lobelias send up red blooming towers of showy, vibrant petals which make these plants impressive in any NSP.
Dwarf water clover
Zones: Six to 11.
Exposure: Part shade to full shade.
Height: Up to 101 mm (4 in.).
Planting depth: Moist soil and will tolerate a water depth of approximately 51 mm (2 in.). This four-leaf clover, a close relative to the ferns, is ideal for table-top or bowl water gardens. It is also often the first to have foliage in the early spring.