Which are NOT perennials?

The correct answer indicates that all the listed plants are not perennials. In the context of plant classification, perennials are plants that live for more than two years, typically going through cycles of growth, flowering, and dormancy over a longer period.

Sandbur, Canadian thistle, and Scotch thistle are types of plants that can be more accurately described as annuals or biennials rather than true perennials.

Sandbur is often perceived as an annual grass that completes its life cycle in one growing season. Canadian thistle and Scotch thistle are more accurately described as biennials or short-lived perennials, but they are frequently controlled as if they were annual weeds due to their aggressive growth and ability to rapidly establish and spread in a variety of environments.

By selecting all of the listed plants as not being perennials, the answer captures the essence of their growth habits as they do not conform strictly to the characteristics of long-lived perennials. This highlights important considerations in integrated pest management practices when identifying and managing these species effectively.