It should never be planted without restriction. Horsetail is well known for the silica it contains widely used as a for cleaning and polishing. It grows in a consistent and uniform manner to about 18" tall. It prefers moist soil but will adapt to growing in shallow water to damp sand. Zone 3. Horsetail Rush is actually a member of the fern family and is absent of leaves or flowers. Although it reproduces by spores it spreads mainly by underground runners. Considered to have invasive tendencies, the runners are capable of traveling under sidewalks, walls and even roads. It should be contained in a closed planter outside the pond or in a container in the water garden. Providing boundaries makes it easy to grow and manage.