Epilobium tetragonum

Epilobium tetragonum, commonly known as the square stalked willow herb, is a species of flowering plant in the willowherb family Onagraceae.

Epilobium tetragonum
Flower
Habit
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Myrtales
Family:	Onagraceae
Genus:	Epilobium
Species:	E. tetragonum
Binomial name
Epilobium tetragonum L.

The erect perennial herb typically grows to a height of 0.1 to 1.3 metres (0.3 to 4.3 ft) and can have several stems. It blooms between January and November^{[clarification needed]} and produces pink-purple flowers.

The species has become naturalised in the Perth and Peel regions of Western Australia.^[1]

Description

• 
  Overhead view of small E. tetragonum plant
• 
  Diagram illustrating tetragonal / square arrangement of leaves

Epilobium tetragonum is characterized by its distinctive square-shaped stem, with leaves evenly spaced in a tetragonal arrangement around the stem, giving the plant a square-like appearance. The leaves are hairless and solid green and have a unique shimmer in direct sunlight.^[2]