Thursday, August 27, 2015

Top myths about noxious weeds By Irene Shonle

Noxious weed- Canada Thistle

Summer’s heat brings many things, both good and bad. The snow melts, opening up the high country for hiking, the flowers bloom, the birds sing and make nests, the pine pollen flies, the mosquitoes bite, and the noxious weeds begin to show themselves.
Noxious weeds are defined by the state, and are alien (not native) plants that cause problems for agriculture and ecosystems. Because they arrive in this country without the insects and diseases that help keep them in check in their country of origin, they have a competitive advantage over our native plants, and can cause species extinction on both local and global scales.
 Here are some of the top misconceptions about noxious weeds I’ve heard: 
1.   “Noxious weeds are medicinal plants.” A particularly pernicious misconception around here is the confusion between Musk thistle (Carduus nutans), which is a noxious weed with no medicinal properties, with Milk thistle/Blessed thistle (Silybum marianum), a plant that has been used medicinally for centuries, but does NOT grow wild around here. Scentless chamomile has none of the properties of Roman or German chamomiles.  It is important to be careful about which plants we actually have. For one thing, the person who collects musk thistle will be disappointed by its lack of liver-protecting qualities. For another, it is imperative that we correctly identify any plants we intend to control (there are also native thistles that should be protected). Granted, there are some noxious weeds with medicinal properties (St. Johnswort, mullein, tansy, chicory, wild caraway, and burdock), but they are small percentage of the rest of the state noxious weeds with no medicinal purposes. Further, most of the ones I mentioned are on “list C” of the noxious weed list, which means that they are widespread overall, and less efforts are put towards their control.  These weeds will likely be around in perpetuity for anyone to wildcraft, and I encourage people to harvest as much of them as they like (just please pull the roots, too, and make sure the weeds have not been treated with an herbicide). 
Noxious weed- Mullein

2. Noxious weeds somehow ‘heal’ the land.” I believe this myth has its origins in permaculture, and there is quite a rift in the permaculture community about noxious and invasive plants. While noxious weeds do get a foothold in disturbed and bare land, they can also quickly invade intact ecosystems, reducing biodiversity and changing ecosystem function. We have plenty of native plants that, were there no noxious weeds to get there first, would fill in the bare spots and do a far more effective job. These are called “pioneer species,” and bee plant, gumweed, tansy aster, scorpionweed, and some grasses are examples. Unlike noxious weeds, these pioneer species often act as ‘nurse plants’, harboring and protecting seedlings of longer-lived later successional plants.  
3.      “We cause more harm treating weeds than leaving them alone.” Noxious weeds grow rapidly (8-12% per year or more), and reduce biodiversity. Where oxeye daisy, Canada thistle, leafy spurge, and the knapweeds grow, few of our native flowers can make it. And native plants are what support our native pollinators – if we want to protect these critical species, we need to preserve the plants that support them. We must also consider the birds, elk, rabbits, deer, etc, that all depend on native plants. Weeds can be controlled by pulling, sometimes by biocontrol, and with herbicides. I know herbicides get a bad press, but I have visited many sites where the noxious weeds were controlled with herbicides, and I have seen firsthand the return of diversity and a flourishing ecosystem. Yes, herbicides must be used judiciously and strictly according to label, but they can be a very effective tool, especially when there are too many weeds to control by hand, or the weeds have deep root systems.
Noxious weed- Oxeye daisy

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