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Cirsium is a plant genus that is part of the Asteraceae family. It contains about 200 species of annuals, biennials, and perennials that are native to North America, Europe, Asia, and regions of northern Africa. Most species have a spiny stem that grows 2-5 feet (61-152 cm) in height and features a single flower, usually with strand-like petals protruding from the flower head. Some of the species in this genus include Cirsium texanum and Cirsium horridulum, which are commonly known as Texas thistle and yellow thistle, respectively.
The Cirsium genus is a wide ranging plant genus that occupies a vast geographic region. Plants within the Cirsium genus are found at sea level and on mountainous terrain. They are found near the arctic regions of Canada as well as in the tropical forests of Central America. Also, the plants grow in swamps, meadows, and deserts.
The Texas thistle is a popular species within the Cirsium genus. It contains a lot of nectar, which attracts several types of pollinators, including bumblebees and butterflies. The larvae of the painted-lady butterfly feeds on the plant foliage, while the goldfinch eats the seeds. The goldfinch also uses the covering of the seeds as nest material.
Classified as a biennial herb, the Texas thistle features leaves that are green on top and grayish on the bottom. The flower head is pink or violet and usually blooms from April to August. It is fairly drought tolerant and can survive on a limited amount of water. The species does require full sunlight rather than partial shade. It is naturally found in prairies in Missouri, Oklahoma, and Texas.
In addition to their ability to attract butterflies and birds to a garden, plants within the Cirsium genus are used for their ornamental aspects. Some gardeners mix and match similar sized plants to create an eclectic arrangement along driveways or entryways. These plants also grow in open pastures.
Some species are invasive and can hinder the growth of other plants, usually by out-competing them for natural resources. One such species is Cirsium vulgare, which is commonly found in grazing fields and pastures. Usually, the growth is so significant, livestock can no longer graze in the area.
The yellow thistle is also considered a weed it grows in pastures or along salt marshes. Usually, this species has spiny leaves and yellow or reddish-purple flowers. The plant is a nectar source for butterflies.