T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Stachys arvensis (Staggerweed)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Lamiales
Family: Lamiaceae
Genus: Stachys
Species: S. arvensis
Binomial name: Stachys arvensis
Common names: Staggerweed , Field woundwort,

Stachys arvensis is a species of small, flowering, annual weed in the mint family. It is native to Europe, Western Asia, and North Africa but it has been introduced to many countries including New Zealand were it is classed as a weed. It is normally found in gardens and crops rather than in pastures this is because it an annual and hence needs bare soil to get established. Stachys arvensis will germinate at any time of the year, particularly in spring and autumn. 

Stachys arvensis has a very hairy, branching stem growing to about 60 centimetres in maximum height. The stem is squared in cross-section. The plant can be prostrate.
The leaves are 2 or 3 centimetres long, oppositely arranged and are hairy and are borne on short petioles. The margins are serrated. 
The inflorescence is made up of interrupted clusters of flowers borne in the axils of the leaf pairs. Each cluster has up to 6 flowers with pinkish corollas in hairy purple-tinged calyces of sepals.

Stachys arvensis gets its common name “Staggerweed” because animals which eat too much of it can develop a health problem known as staggers, which causes them to stagger around.

A developing  inflorescence

Inflorescence flowering

The oppositely arranged leaves.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/