Biennial Weeds

This subset of the plant world includes several of Idaho's noxious and other invasive weeds. As you can probably tell from the name, biennial plants are those which usually live for two years between the time their seeds germinate and when they produce seed and die. During their first growing season, biennials remain in a low growing "rosette" form and put most of their energy into developing a large root system. In their second year they take advantage of the large root system to "bolt" and produce a flower stalk that, if left alone, produces hundreds or thousands of seeds that can be widely spread. About the only good news about this group is that you generally have two years to get them before they produce seed. As with the annual weeds, biennials rely entirely on seed production for reproduction, so stopping seed production is the key to control. Also like the annual weeds, "stopping seed production" is easy to say, but very difficult because of the various adaptions these plants have for survival. In northern Idaho this group includes the noxious weeds houndstongue (aka the velcro plant), tansy ragwort (this is not common tansy) and Scotch thistle and the obnoxious weed burdock (another velcro plant). I know that burdock is in the City of Sandpoint. Burdock and houndstongue both produce seeds that are known to most anyone who owns pets or livestock or spends time outdoors. These both spread by attaching to any critter that brushes against it, including us, so for both of these we have met the enemy and he is us.

Control: There is a little more good news hidden here and in the Annual Weed post. Both of these groups of weeds can be effectively controlled in yards and other small areas by simply pulling them up or cutting them off at the root or tilling them under, AND, (the kicker) keeping at it for years, BEFORE THEY PRODUCE SEED. Anything done after seed production with any of these weeds is only improving appearances, because the seeds are all ready on the ground. However, with vigilance and persistent effort you can expect to eliminate these from your yards. The story is a little different for perennial weeds, which will be talked about in the next post. Stay tuned and remember: don't let them go to flower. This pic shows early season houndstongue 'rosettes'. They are the most robust plant out there early in the spring.