Herb Robert (Geranium robertianum) is a branching, low-growing winter and spring annual. It has five-petaled pink flowers and deeply dissected light green leaves that release a pungent odor when crushed. Leaves turn red as the plant matures and the stalks get brittle. The roots are shallow so it’s easy to pull by hand but be sure to pull early as the plant spreads by seed, which are inside long pointed capsules that fly off the plant when it’s touched. Its very difficult to make much headway if the seeds are being thrown into the soil all around you, waiting to sprout! Also, the seeds can stay viable for up to five years.
Herb Robert is one of the worst woodland invaders, because of how the seeds are thrown out when it’s disturbed by wildlife, pets, gardeners, walkers and hikers. This is why we ask folks to brush off their boots, clothes, tools, bicycles and pets after visiting infested areas. In addition, the plant can tolerate a lot of different growing conditions, spreading into dense patches that can contain up to 250 plants per square meter.