"Woad Rage"
There are many definitions of what constitutes a weed: a plant out of place, an unwanted plant, a plant growing in a place not wanted by humans. Then there are the most dangerous weeds of all; species capable of altering ecosystem processes such as nutrient cycling, intensity and frequency of fire, hydrological cycles, soil chemistry, etc. Dyer's woad (Isatis tinctoria) is a weed species designated for control in Trinity County because of its ability to alter the surrounding soil chemistry (allelopathic) making it difficult for native species to survive and reproduce.
Alleopathy can affect many aspects of plant ecology including occurrence, growth, plant succession, dominance, diversity, and plant productivity. Different plant parts, including flowers, leaves, leaf litter, stems, bark and roots can have allelopathic activity that vary over a growing season.
Understanding the effects of allelopathy on native plant populations and on a particularly sensitive plant Shasta chaenactis (Chaenactis suffrutescens) the Trinity County Weed Management Coorperative (TCWMC) has targeted this species for control. Where can this species be found? It is found along Hwy. 3 North, Hwy. 299 west of Weaverville and in our own yards.
This plant starts out as a low-lying rosette. Winter chilling is necessary for the plants to bolt to produce bright four-petaled yellow flowers. Average stem growth during the bolting stage has been measured at a rate of 4 inches per week. Flowering is seen as early as April, with seeds maturing in June or July. Dyers woad produces a tap root 3-5 feet long. This member of the mustard family produces an average of 350-500 seeds per plant, with some plants producing well over 10,000 seeds in one year. Early recognition and immediate treatment are the most economically efficient means of controlling Dyer's woad. Control by hand pulling is most effective during the plants first growing season when it is in the rosette stage and the taproot is not developed. Removing only the top growth will not kill a plant with a well developed root system, because of its ability to form shoots from the portion of root left in the ground. The "rage" against woad is a difficult one, because of its many tactics for invading disturbed areas. Woad be onto you and me if we don't stop this
invasive species. Woad you help us?
How can you help protect our native plant communities? The District, as a member of the Weed Management Cooperative, is asking you to help us identify leading pioneer infestations. Weed species that have been identified for control include: Hoary Cress/whitetop, Dalmation toadflax, Diffuse knapweed, Perennial peppergrass, Tree-of-Heaven and Yellow star thistle. If you have observed any of the above mentioned species, please fill out the following form. You can fax, mail or drop off the form at the Trinity County Resource Conservation District office. If we are diligent in our efforts, we will successfully maintain plant diversity and balanced ecosystem for the enjoyment and perpetuation of future generations.
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