Which of the following is a common grass weed in ornamental settings in Iowa?

Quackgrass is indeed a common grass weed found in ornamental settings in Iowa. This perennial grass is known for its vigorous growth and can quickly become invasive in landscaped areas. Its ability to spread through extensive underground rhizomes makes it particularly challenging to control, as it can outcompete desirable ornamental plants for nutrients and water.

In contrast, yellow nutsedge is a sedge rather than a grass and typically thrives in wet conditions, making it more prevalent in areas with poor drainage rather than typical ornamental gardens. Common chickweed is a broadleaf weed that, while common in gardens, is not classified as a grass. Canada thistle is also a broadleaf weed and tends to grow in disturbed areas, making it less common in well-maintained ornamental settings compared to quackgrass. Understanding the specific characteristics and growth habits of these weeds helps in effective management and control strategies in ornamental horticulture.