Inaction on thistles costs money

Spear Thistle Cirsium vulgare. A large spear thistle rosette covers about one-third of a square metre, and because it is not readily grazed by stock, the carrying capacity of paddocks with dense patches of thistle is reduced considerably. In a survey carried out in a New Zealand study where for every additional thistle per square metre in pasture there was a decrease of 1.68 kg in the live weight gain of sheep. In addition to direct competition, the spiny nature of the thistle also deters animals from grazing pasture in the vicinity and patches may become so dense that that are impenetrable to stock. Another disadvantage is that contaminated hay is downgraded in quality and price. Sheep grazing encourages spear thistle by reducing competition from neighbouring plants. This is reflected in increased thistle growth, flowering and seed production on heavily grazed pastures. In contrast, thistles are usually sparse on ungrazed sites. This weed readily establishes in high fertile soils which is bare of vegetation at the end of summer. Local landholders recently have expressed great concern about the amount of thistles on some neighbouring properties, landholders are reminded that it is an offence under the CALP act not to control and eliminate this weed. Isolated patches can be grubbed out but most of the root system should be removed. Target the rosette stage with a selective herbicide; ensure there is competition from other plants that can replace the weed. Follow up your work and be persistent in implementing a long term management plan.