Lepidium bonariense.
From South America Cut-leaf peppercress is naturalised in S. E. Queensland
where it is a common environmental weed.
Plants, lasting for 1 or 2 years are erect herbs up to 60 cm high.
The stems have some fine hairs that may point down the stem.
Leaves are in 2 sections – a basal rosette and stem or cauline leaves.
The basal leaves, up to around 8 cm long are on a petiole.
The petiole, and more obviously the midrib are winged.
The blade is dissected to (pinnatifid) or near (pinnatisect) the midrib.
Lobes, 1 to 2 mm wide may be dissected once or twice more.
Lower stem leaves resemble the basal ones but get progressively shorter up the stem.
Upper stem leaves have no petiole and the short blades are only once divided.
Leaves, mainly the upper ones have a few hairs on the edges and midribs.
The basal and lower stem leaves are deciduous.
Terminal inflorescences are a dense cluster of tiny flowers at the tip of an elongating midrib
with developing fruit below.
Flower stalks (pedicels) have short hairs on the upper surface.
There are 4 sepals that alternate with the 4 petals.
Green sepals, around 1 mm long have a reddish edge and tip.
There are longish hairs on the sepal that lies above those on the pedicel.
The linear white petals, around 0.5 mm long have no hairs.
There are 2 (4) median stamens with 1 opposite each side of the flattened ovary.
The superior green ovary is roughly round with a shallow notch at the top.
The stigma, on a short or no style lies in the notch.
There is a narrow false septum dividing the single locule into 2 chambers each with 1 ovule.
The fruit (silicula) are a flattened almost circular capsule.
They are 2 to 4 mm long and 2 to 3 mm wide.
The pedicels lengthen to be up to 5 mm long on mature capsules.
The capsule is smooth but the hairs on the upper surface of the pedicel remain.
There is a ridge down the front and back where the septum is attached.
The stigma lies in a shallow notch formed by short wings on the upper part of the capsule edges.
The 2 brown seeds are 1 to 2 mm long.
J.F.
