The biology of Canadian weeds: 158. Galega officinalis L.
The biology of the weed goat's-rue, Galega officinalis (Fabaceae), is reviewed. Introduced to Canada in the late 19th Century as an ornamental, it has become established at scattered localities and is spreading locally in southern Ontario. The plant is considered a noxious weed and is legally regulated in many jurisdictions due to the production of toxic alkaloids and its invasive characteristics. Primarily a weed of pastures, grasslands and perennial crops, it also displaces native vegetation in areas where it becomes established. Originally endemic in the Black Sea region, it was spread by humans through Europe and eastward to Pakistan as a herbal medicine. More recently it has been introduced widely as a forage and ornamental plant. As a folk remedy it has been used primarily to treat diabetes in humans and to enhance milk production in both humans and livestock. The plant has also been used as a forage by limiting consumption to early growth stages and the quantity ingested. Effective control has been achieved with 2,4-D, dicamba, tryclopyr, metsulfuron methyl and other herbicides. Goat's-rue forms a highly specific nitrogen-fixing symbiosis with the soil bacterium Neorhizobium galegae symbiovar officinalis. Successful establishment of Goat's rue in new regions depends on the co-introduction of plant and bacterium. The lack of long-distance dispersal adaptations, soil pH requirements and its symbiont dependency, reduces the ability of G. officinalis to spread into novel areas without anthropogenic activities. These constraints to establishment may facilitate management and eradication strategies.