Known as the knotweed or buckwheat family with up to 1200 species including
Antigonon, Muehlenbeckia, Triplaris and Rumex.
Australia has 12 genera and 57 species.
Most are herbs but there are some trees, shrubs, lianas and vines.
The simple leaves are mostly alternately arranged in a spiral.
They may or may not have a stalk and some have swollen nodes on the stems.
Leaves may have 2 fused stipules forming a short membranous tube around the stem (an ocrea).
Inflorescences have a similar sheath at the base.
Where there is more than one flower each one has a similar sheath.
Flowers can be bisexual or individual plants may have only male or female flowers.
The perianth usually has 3 to 6 tepals either free or with their bases joined.
The outer tepals may be green like sepals and the inner ones petal-like in white or pink.
The outer tepals may enlarge and surround the fruit.
The 3 to 9 stamens, separate or with fused bases, are usually in 2 whorls.
They may be of different lengths and their anthers open inwards via longitudinal slits.
The superior ovary usually has 3 carpels that fuse so there is only 1 locule with 1 ovule.
There are as many styles as carpels and they may be free or fused at the base.
Each style, or branch, ends in a stigma.
Nectaries are often present either discrete at the base of the stamens or as a disc.
The fruit is usually an achene (a small, indehiscent fruit with a single locule).
It is usually 3-angled or biconvex and covered by the persistent perianth.
The fruit can be winged.