Herb Robert is a small geranium from Europe that has spread widely through the shady lower forests west of the Cascades. The Oregon Department of Agriculture lists it as a Class B noxious weed, and the state quarantine bars selling or transporting the plants and seeds. Its nickname, Stinky Bob, comes from the sharp smell of the crushed leaves.
It reproduces only by seed, and it is very good at it. Ripe capsules end in a long beak and can fling seeds as far as 20 feet when brushed, and seeds also hitch rides on boots, fur and garden waste. The flowers usually fertilize themselves, seedlings sprout in fall or spring, and seeds can survive in the soil for up to five years. The plant handles deep shade as well as sun, does best along forest edges and in open woods, and can move into undisturbed forest where it crowds out native wildflowers.
Visitors notice it along trails, campgrounds and road edges, with small pink flowers from spring through summer and foliage that turns red in bright light or as plants age. Its roots are shallow, so it pulls up easily. Plants that have already flowered are best bagged and put in the trash rather than composted, so their seeds do not spread.
How to identify it
A sprawling to upright annual, usually under 2 feet tall, with hairy, often reddish stems that break easily at swollen joints. Leaves are deeply divided into fernlike segments and smell pungent when crushed. Flowers are about half an inch across with five pink petals, usually in pairs, and are followed by seed capsules with a long, pointed beak.
Look-alikes
Before it flowers, a young plant can be mistaken for the native Pacific bleeding heart, which also has finely divided leaves. Herb Robert's pungent smell when crushed and its hairy, often reddish stems are good checks.
Habitat
Shady, moist forest understory, forest edges, streamsides and disturbed ground such as trailsides and campgrounds, mostly in lower forests west of the Cascades and in the Columbia River Gorge. It grows best in open woods and along edges but also tolerates sunny, dry and rocky spots.
Sightings in the forest
846 research-grade sightings in Mt. Hood National Forest on iNaturalist, most recently on November 1, 2026. See them on iNaturalist →