Which perennial weed resembles bent grass and can turn whitish or brown in winter?

Nimblewill is the correct answer because it is a perennial grass that closely resembles bent grass, especially when it's in its vegetative stage. Its fine leaf texture and growth habit can make it difficult to distinguish from other desirable turf grasses like bent grass. During the winter months, nimblewill often turns whitish or brown, which is a characteristic sign of this weed. This color change occurs as the plant goes dormant in response to colder temperatures, making it more noticeable against the green backdrop of healthier turf.

Nutsedge, while a problematic weed, does not resemble bent grass and typically remains green in the winter. Crabgrass is an annual weed, primarily germinating in the spring and not persisting through winter in the same manner. Wild onion is identified by its distinctive bulb and growth habit, which is quite different from both bent grass and nimblewill, lacking the fine texture and growth form of these grass-like plants. Understanding these differences is crucial for effective identification and management of turf pests and weeds.