Of the following, which has the smallest seed?

Bent grass is known for having the smallest seed size among the options listed. Its seeds are typically very fine and small, which gives it specific advantages in certain applications, such as creating smooth, low-height turf that is often preferred on golf courses, particularly for putting greens. This smaller seed size allows for quicker germination and establishment in the right conditions, making it a popular choice for fine turf projects.

Perennial ryegrass, tall fescue, and Kentucky bluegrass all have relatively larger seeds compared to bent grass. Specifically, perennial ryegrass seeds are larger than those of bent grass, while tall fescue has even larger seeds that are more robust and designed to thrive in various environments. Kentucky bluegrass seeds are also larger and have a different growth habit and lawn appearance than bent grass. The variance in seed size reflects the different characteristics and intended uses of each grass type.