It is important to keep in mind that several mowing events per year might be needed to reduce plant populations due to maturity differences. Mowing can only be beneficial if applied when the thistle is at the early bud growth stage and before seed production. Mowing can be used as a mechanical control method to reduce infestations of biennial species. Be sure to review teh label before application, always use the label rate, and observe grazing and haying restrictions. Specific rates will vary between products. Suggested rates are generalized by active ingredient. They are included here only for educational purposes. The mention of any product is not and should not be construed as an endorsement for that product. Data adapted from the USDA Plant Database ( plants.sc./).Īdapted from Seller et al., 2019 and Dillard et al., 2019 Thistle species distribution across the southern USA. Flowering will occur from late spring to mid-summer for approximately a month and seeds are easily transported by wind. The leaflets are the base of the flower- head are dull green, hairless, and vertically overlap each other. The flower head is formed by numerous yellow florets. Leaves might have a tinted reddish- purple color at the base. Lower Leaves have deep triangular lobes and margins are dentate with soft prickles while upper leaves look more entire with shallow lobes. Leaves are sparsely distributed in the stem and they become smaller as they ascend in the main stem. The stem has no hair except for the is the flowerhead will form. It is adapted to full sun or part shade.Ĭommon Sowthistle (Sonchus oleraceus) is a winter and spring annual that can grow up to 4 feet tall. Seeds are heavier than other thistle species and are not easily transported by wind. A plant can produce from 6,000 to 8,000 per year and remain viable for up to 10 years. This thistle can flower from April to October. It forms large rosettes in which single cottony stems can produce purple flowers that are surrounded by leath- ery, spiny leaflets. The leaves are oblong to lanceolate, smooth with shiny dark green color and a distinctive white pattern running along the veins. It is a very deep white tap-rooted bienni- al. Milk thistle (Silybum marianum) can form a dense stand and grow to 6 feet tall. The base of the flower is surrounded by numerous spiny basal leaflets. Yellow flowers are formed at the end of the branches and are almost hidden by the upper leaves and they appear from May to September while seed will not mature from July to October. The leathery leaves are more or less hairy with lobed, spiny margins. It has a coarse, erect, branched, and a rather woolly stem. Although bull thistle seeds can germinate easily, seeding survival is very low.īlessed thistle (Cirsium vulgare) is an annual thistle that can grow up to 2 feet. The purple flower is gumdrop-shaped with long, hard yellow spines. ![]() Bull thistle tends to flower later than other thistles from June to September. The ro- sette tends to very hairy with dark purple ribs. ![]() Leaves have distinctive hairs with a prickly appear- ance on the upper side and cottony on the lower side, especially during the rosette ad early bolt growth stages. A third of the seed produced might germinate.īull thistle (Cirsium vulgare) is easy to identify by the bushy appearance with deeply double toothed leaf margins and very prominent hard spines. It can produce flowers at any time for about 10 weeks starting in late May. Rosettes (thistle forms a low-growing ring of leaves) tend to be dark green with a light green midrib, smooth leaves, and they can reach more than 2 feet in diameter. The flowers tend to droop with brown leaflets resembling pinecones. It produces very large, single, and deep rose flowers. It is commonly found in dry or overgrazed areas reaching a growth height of 6 feet or more. Musk thistle (Carduus nutans) is also known as nodding thistle and it is probably one of the most common biennial this- tles found in southern pastures. Usually mowing as a control method is not enough and a program that impacts the root system must be imple- mented. Perennial thistles are more difficult to control than biennial because they can reproduce by root or seed. These biennial thistles will only reproduce by seed and depending on species, they can produce large seed heads from May to October with seed numbers of 8,000 to 120,000 seeds per plant and they can be easily transported by wind. They can overwinter as a rosette while resuming their vegetative growth in the spring, bolt (the stage is when the thistle forms a stalk and prepares to flower), and flower. Most biennial thistles dominate overgrazed areas, and they germinate in the summer and fall.
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