Which of the following are examples of biennial weeds?

Biennial weeds are plants that complete their life cycle over two growing seasons. In the first year, they typically germinate and establish themselves as rosettes, developing leaves and roots but not flowering. During the second year, they flower, produce seeds, and die off.

The option identifying musk thistle, mullein, and hound's tooth fits this definition perfectly. Musk thistle (Carduus nutans) is known for its biennial life cycle, where it establishes in the first year and then flowers in the second. Mullein (Verbascum thapsus) also exhibits this biennial behavior, forming a rosette in its first year and then sending up a flowering spike in the second year. Hound's tooth (often referring to various species of plantain) similarly follows a biennial growth pattern.

In contrast, the other options contain plants that do not adhere to the biennial life cycle. Dandelion, crabgrass, and foxtail are primarily classified as perennial or annual weeds, while annual bluegrass, chickweed, and henbit tend to be annual plants. Quackgrass, bindweed, and yellow nutsedge are typically perennial weeds, which can regrow