Question of the Week
Answer: Fiddleneck (Amsinckia spp.) is a native annual herb in the borage family. Fiddleneck is known to be toxic to horses both in its fresh form as well as in hay (Weed Board, 2010), and this toxicity is likely caused by alkaloids in the plant tissues (Merck, 2008).
The presence of high numbers of weeds like fiddleneck is a sign that something is happening in the field that may weaken grasses and decrease productivity. As long as a grass stand is maintained intact through proper management, the grass community will thrive. However, when some kind of disturbance occurs, the grasses often have a hard time bouncing back without weed populations becoming established. Weeds take advantage of a niche left open by grasses as they disappear. Grass plants cannot occupy the available niche as easily as weeds can, because weeds have evolved to be very competitive for nutrients and have adapted to soil conditions that most grasses have not. If a soil is disturbed through compaction (the destruction of soil structure due to animal impact or machinery), or if it has become infertile due to intensive cropping and harvesting of nutrients, weed species will find a comfortable home. This is nature's way of correcting imbalances because deep-rooted weeds can scavenge non-available nutrients, translocate them to their leaves and stems, and return them to the soil when they die. This is, in effect, a way of soil building in degraded soils. After the soil has become porous due to the rooting of weeds, and nutrients have been returned to the soil, natural plant succession can take over and the grasses will begin to return (Cocannouer, 1950). However, without human intervention, this succession can take decades to occur.
So, weeds are good indicators of soil nutrient deficiencies and excesses. For instance, fiddleneck tends to occur in soils that are low in calcium and very high in magnesium, potassium, and manganese (McCaman, 1994). Fiddleneck can often be found on soils that are low in humus and low in soil porosity. The presence of this high numbers of this plant might suggest that soil calcium is limited and should be brought into balance with other nutrients, including carbon in the form of compost or manure.
Fiddleneck does not compete well with grasses. A dense, highly productive pasture with fertile soil and good grazing management is the best defense against annual weed infestation, including fiddleneck. Highly productive pastures can be inherently resilient and maintaining a dense, productive pasture includes fostering plant diversity and managing defoliation through mowing or grazing to benefit beneficial plants while discouraging weeds.
The presence of weeds in an established pasture is usually a sign of a management problem. Fertility, proper planting procedure, and harvest management are the most effective ways to maintain dense, productive pastures. Ensure adequate soil fertility and optimum pH with nitrogen-fixing legumes and applications of lime as per soil test. When establishing new pastures, ensure that you use weed-free seed on a well-prepared seedbed, or use a no-till drill at the appropriate time. Also, be sure to practice good harvest management, whether grazing or haying, by leaving enough forage standing after harvest to allow for regrowth. It is especially important to rest pasture plants after grazing to allow full regrowth, thereby ensuring plant health and productivity.
Fiddleneck should be controlled by mowing. A single summer mowing is usually beneficial after flowering but before the seeds set. However, additional clippings will be required if later summer rain results in significant lush fiddleneck regrowth. Mowing after flowering but before seed set will reduce weed seed production and decrease the amount of weed seeds in the soil for the following year.
Cocannouer, Joseph A. 1950. Weeds Guardians of the Soil. The Devin-Adair Company.
McCaman, Jay L. 1994. Weeds and Why They Grow. Sand Lake, MI.
Merck. 2008. Pyrrolizidine Alkaloidosis: Introduction, The Merck Veterinary Manual. Merck & Co., Inc. Whitehouse Station, NJ.
USDA-NRCS Plants Profile, Amsinckia Lehm (fiddleneck)
Weed Board. 2010. Fiddleneck. Stevens County Noxious Weed Control Board, Colville, WA.
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