It is not only helpful to know which weeds are noxious but also what methods are effective in eradicating them. Here are a few items of interest regarding some of the more commonly found noxious weeds in our area.
Some plants placed in gardens for ornamental purposes are so suited to the habitat that they easily spread outside the bounds of the garden, eliminating less aggressive plants in their wake. This has been the case here in the Fraser Valley, especially with the pleasant looking oxeye daisy.
This plant is biennial - it only lives two years. The first year is vegetative; the second year, it blooms and later dies. During the second year, after the blooms drop, the viable seeds spread via wind, birds, and human activity. If pulled during the first year, it can be destroyed. When the plant blooms it can still be pulled and the plant will be destroyed. However, once the seeds drop, the plant cycle begins anew. The seed of scentless chamomile may remain viable in the soil for 4 to 6 years and a single plant can produce 960,000 seeds in one season! Eradicate this weed from your home garden by pulling it each year as you notice its growth or by chemicals labeled for use at an early growth stage.
This perennial plant comes back every year, for as many years as it can survive. Because of its extensive root system, simply pulling the part of the plant above ground does nothing to destroy the plant below ground. Systemic herbicides, which attack the root system, are the only sure method of destroying this plant.
Oxeye daisy is also perennial. Its flowers are similar to chamomile, but its leaves are serrated, not fringed as are those of the chamomile. It is also similar to the Shasta daisy, which, although not native, is not particularly aggressive at this time. Like Canada thistle, the oxeye daisy survives year after year; however, its roots are not as deep so digging up the plant’s roots is an effective mechanical (or cultural) method of destroying this plant. Do not plant as an ornamental.
Common tansy is also perennial. This plant is common in Fraser, and is sometimes found in flowerbeds or used as a hedge. Some think it resembles the yarrow plant. It was introduced as an ornamental; however, due to its aggressive nature, it has escaped and is taking over native plants. It can be destroyed only by systemic herbicides. The State has specifically requested eradication of this plant in Fraser because ours is one of the few locations in Grand County where it is found. Ultimately, the goal is to have common tansy eradicated state-wide by 2016.