Family Amaranthaceae > Subfamily Amaranthoideae.
There are 60 to 100 species with Mabberley accepting 75.
Species can be difficult to define as features are variable even in a single species and hybridisation is easy.

They are annual or short-lived perennial herbs with deep fibrous roots.
They may be prostrate or bushy erect plants up to 2.5 m high.
The grooved cylindrical stems can be green, red or purple.
Some species have short simple or multicellular hairs.

The mostly alternate leaves, up to 15 or 20 cm long are on a long petiole.
The ovate to elliptic blades can be green, crimson, maroon, purple or yellow.

Terminal and axillary inflorescences, erect or pendulous are up to 60 cm long.
They have small densely packed flowers each with a bristly bract and 2 bracteoles.
Flowers are unisexual with almost 90% of species having both on the same plant.

Flowers have no petals but 3 to 5 tepals that are free or joined at the base.
They can be thin and membranous or red, crimson, purple, maroon, pink or greenish as well as white or cream.
Male flowers have 3 to 5 free stamens with 2 pollen sacs (thecae).
Female flowers have a superior ovary of 2 or 3 fused carpels with one locule with 1 basally attached ovule.
There are 2 or 3 styles and stigmas.

The fruit are a dry capsule that ruptures irregularly or the top lifts off like a lid (operculum).
The stigmas may form 2 or 3 beaks on the top.
Each capsule has a shiny circular seed 1 to 1.5 mm across.
They can be black or coloured.