For more info, go to vtinvasives.org where the information below has been obtained.
CAUTION: When sap on skin is exposed to sunlight, creates a chemical burn, which is a potential hazard for landowners or road crews mowing/weed-whacking it, as well as people walking in infested areas.
For new infestations:
New infestations should be treated rapidly before an extensive root system is established. Hand pull or dig up plants to ensure the entire tap root is removed. Check the site the next year for new growth.
For large infestations:
Mowing large patches of chervil will prevent it from setting seed. Do not mow after June, when the plant has already set its seeds. Clean all equipment well before using again. If possible, after mowing, cover ground with thick plastic or other ground cover.
Reproductive Strategy / Lifecycle:
Garlic mustard reproduces exclusively by seed, and it is a prolific seeder. Each mature plant can produce hundreds of seeds (average is between 130-300 seeds per plant, although plants have been found to produce as high as 7900 seeds per plant). Seeds are viable for 4 to 7 years. Although the majority of the seeds that are produced are viable, relatively few actually germinate (this is dependant by site conditions). About 40% of seedlings reach adult stage (a mature, flowering plant). Seeds are cast by mature plants in late June, July and August and lie dormant for 18-20 months. Seedlings emerge in the spring and become basal rosettes by the fall. Rosettes stay green through the winter and as a second year plant produce a flower stalk the following spring. Mature plants flower in May and set seed in late June, July or August.
Cut stalks at least once per month throughout the growing season. Use a scythe, loppers or even a lawn mower, depending upon the ground surface you are working on. Repeat cuts for five years. Do not replant until the knotweed is under control and the plants are much smaller and have lost their vigor. Replant with good sized natives.
“Japanese knotweed is an upright, shrublike, herbaceous perennial that can grow to over 10 feet in height. As with all members of this family, the base of the stem above each joint is surrounded by a membranous sheath. Stems of Japanese knotweed are smooth, stout and swollen at joints where the leaf meets the stem. Although leaf size may vary, they are normally about 6 inches long by 3 to 4 inches wide, broadly oval to somewhat triangular and pointed at the tip. The minute greenish-white flowers occur in attractive, branched sprays in summer and are followed soon after by small winged fruits. Seeds are triangular, shiny, and very small, about 1/10 inch long.” (source: Plant Conservation Alliance Working Group http://www.nps.gov/plants/alien/fact/faja1.htm)