Monday, March 1, 2010

Herb Robert (Geranium robertianum)

General Description: Herb Robert is both a winter and a spring annual. It is a low growing plant.

* deeply dissected
* light green in color
* in late fall, foliage turns red. Also turn red with sufficient light.
* when crushed has a pungent odor

* pink
* five petals

* fork
* brittle at the joints


Herb Robert is a Class B invasive weed and poses a tremendous threat to forest understories and to plant biodiversity in forests of western Washington.
Because it was garden plant there have likely been numerous independent introductions.
This tough little plant adapts and thrives in a variety of exposures, moisture levels and soils (even germinating in rock crevices). It can be found it just about everywhere, from urban environments to undisturbed wilderness areas.
Because it is so adaptive, it out-competes native flora until it carpets the forest floor.

Propagated by seed, the plant is able to eject its seed as far as 15 to 20 feet. The seeds also have sticky threads, that help them catch a ride on leaves, animals and even passing ants and snails.
Germination is quick and the rosettes overwinter, flowering in late Spring and to late Summer.

Pulling the plant before bloom is the best weed control strategy. It has little root structure and can be pulled easily, but because the stems are brittle, the plant must be grasped at the base.
The removed plants must be bagged as they are pulled, to contain seed and the possibility of continued fruiting.
Pulling the plant also improves the "seedbed" for remaining dormant Herb Robert seeds and therefore the site must be revisited and monitored.

This geranium can look like the delicate and highly desirable native bleeding heart! Please do not pull weeds until the identification is absolute.

There is a scheduled Herb Robert clinic and work party to remove Herb Robert, from the Hansville Greenway, on Sunday March 7 starting at 11/am.
The group will be meeting at the southernmost place on NE Spruce drive (closest to post 15) and will work between posts 14-16.
Cover your arms and hands for good protection from nettles and bring a plastic bag to contain weeds.
Since this area contains both Herb Robert and Bleeding heart, this outing will be a great hands-on educational opportunity as well as an invaluable service to the health and vitality our own Greenway.

If you would like to participate, please contact Jo Roberts ( for details and directions.


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