Northern Willowherb

Evening-primrose (Onagraceae family):

Epilobium ciliatum Raf.

EPPO code:

EPIAC

Other names:

Fringed willowherb

Species information

Lifecycle:

Perennial.

Propagation:

Reproduces by seed and possibly underground root buds.

Emergence:

Typically germinates in the spring and fall.

Habitat:

Northern willowherb is found throughout Ontario, but it grows most commonly in moist places, along roadsides and in waste areas. More recently, it has been found on occasion in no-till fields planted to glyphosate tolerant soybeans. It appears to be tolerant to glyphosate.

Competitiveness:

No data exits on the competitiveness of northern willowherb. One study indicates, however, that soil that contains rye root residues will lower seed germination of willowherb (Przepiorkowski and Gorski, 1994).

Identification clues

Seedling

Cotyledons:

Egg-shaped to rectangular (rhomboid), small.

Young leaves:

Northern willowherb’s first leaves are long-oval and opposite. Subsequent leaves are lance-shaped and opposite.

Mature leaves:

Mature leaves are thickly veined, opposite, lance-shaped and have finely- toothed margins. They are opposite but become alternate near the top.

Mature plant

Stem:

Northern willowherb’s stem is branched to erect, grows 1.5 m or taller and is covered in bristly hairs.

Flowers:

Its flowers are small and have four pink to purple petals that are lobed (giving it the appearance of eight petals) and stamens that have yellow anthers on purplish filaments.

Fruit:

Slender, straight, cylindrical seedpods with four chambers contain egg-shaped seeds that are flattened and end with a tuft of long, soft hairs.

Roots:

Creeping root system.