Which plant is characterized by closely spaced greens that grow curled on a string?

The plant characterized by closely spaced greens that grow curled on a string is Smilax. Smilax is a type of vine that has tendrils which can create a distinctive appearance; its leaves often appear thick and can be somewhat curled, contributing to the visual effect of being 'curled on a string.' This characteristic makes Smilax easily identifiable among other plants.

In contrast, the other options present different growth forms: Myrtle is known for its aromatic leaves and flowers, Bamboo features jointed stems and a notable upright growth pattern, while Willow is recognized for its long, slender stems and drooping foliage. These distinct characteristics set them apart from Smilax, affirming that the correct answer indeed reflects the unique curled, closely spaced greens.