Family Onagraceae > Subfamily Onagroideae > Tribe Onagreae.
The correct botanical name is now Oenothera but they are still commonly known as Gaura.
There are around 21 Gaura species in subsection Gaura of the Oenothera genus.
Native to North America some are now widely naturalised and a few are weeds.

Mostly perennial herbs some are annual or biennial.
A plant can have one or more branched or unbranched stems up to 1.5 or 2 m long.
The round or angled stems can be erect or spreading and occasionally prostrate.
In older plants the lower part of the stems may be woody.
Mature plants can be sparse, shrub-like or form dense clumps or thickets.
Stems have a variety of hairs that may wear off with age.
Hairs can be sparse or dense, simple (spreading or lying flat) or glandular.

The alternate leaves in the basal rosette are up to 15 cm long.
The cauline leaves, spread out along the stem are from 13 cm long at the base down to 1 or 2 cm at the top.
They are all narrowly elliptic or lanceolate with a pointed tip and a wedge-shaped base.
The often wavy edge can be smooth, have a few to many small to large teeth or have 1 or more basal lobes each side.
There may be no hairs or one or both surfaces can have sparse to dense hairs that are often lost as the plant ages.
The basal rosette dies off and some of the cauline leaves may fall when the plant flowers.
The lower leaves sometimes become a deep maroon or reddish colour.

The solitary flowers along the spike-like or branched inflorescences open from the base up.
Each of the few to 40 or so flowers on a spike or branch has a small lanceolate to ovate leaf-like bract at the base.
The erect or spreading, round or angled stems may have simple or glandular hairs.
Flowers, often with no stalk are around 2 to 3 cm long and only last one day.
The cylindrical or angular hypanthium (floral tube) is usually around 2 to 15 mm long.
The inner surface, or occasionally only its upper half is covered in straight or tangled hairs.
There are 4 nectaries at the base.

There are (3) 4 linear to lanceolate sepals up to 18 mm long and 2 mm wide.
They may be smooth or have long or short hairs.
Their edges are stuck together until the flower opens when the sepals split onto 1 to 4 units.
The sepals bend back sharply (reflexed) and fall off at or after flowering time.

The (3) 4 petals lie in a semi-circle in the upper half of the flower.
From 2 up to 25 mm long they are elliptic or oblanceolate often with a clawed base.
They are white or pink (yellow) and often become reddish or purplish with age.

The (6) 8 stamens have filaments from 0.3 to 13 mm long sometimes with a small appendage or scale at the base.
The ovate to linear dorsifixed anthers are up to 5 mm long.

The inferior ovary, with 4 ridges initially has (3) 4 locules each with 1 or 2 ovules.
The walls between the locules may break down and ovules abort often leaving a single locule with 1 ovule.
The style, up to 3.5 cm long may have hairs on it.
The 4 linear stigma lobes have a cup-like indusium below them.

The fruit are indehiscent ovoid to ellipsoid woody capsules under 1 cm long.
In cross section they can be round or have (3) 4 shallow or prominent ridges or wings.
New plants grow from the tiny seeds or from the rhizomes.