The Cat-tail family are monocots.
The Plant List recognises 65 species and Mabberley around 26 in the 2 genera.
Most are in the Sparganium genus and a few in Typha.

They are perennial grass-like herbs growing in wetlands.
The unbranched stems grow from rhizomes that spread laterally in the ground.
The basal leaves alternate in 2 ranks.
Their overlapping bases sheath the stem with the edges of the sheath being open.
The long flat narrow blades have a pointed tip and parallel veins.

Terminal inflorescences have densely packed flowers in 2 sections with the males above the females.
In Typha the sections are cylindrical and in Sparganium they are globular.
Flowers can have 3 to 6 tepals or just hairs, bristles or scales.

Male flowers, on a short stalk have no sepals or petals but there are up to 8 thin bristles.
There are also scales scattered between the flowers.
There are 1 to 8 stamens with basifixed anthers opening through longitudinal slits.
There may be long hairs on the filaments.
The connective tissue between the pollen sacs (thecae) extends up as a wide appendage.
After pollen release the male flowers fall but the bare top of the spike usually remains.

The perianth of female flowers is reduced to numerous hairs or scales.
The superior ovary, from 1 carpel has 1 ovule in the single locule.
The ovary, on a stalk with long hairs has 1 style and a long stigma.

The achene-like Typha fruit have the style still attached.
They split to release the seed with the attached hairs or scales aiding its wind dispersed.
Sparganium fruit are drupes.