Turfgrasses are monocotyledonous plants (having only one seed leaf in the embryo) whose growing point is at the crown near the soil. This low and protected location of the growing point permits turfgrasses to be mown and walked on repeatedly.
Most turfgrasses used in landscapes nationwide are perennial, although there are several annual species of significance. Most species reproduce from seed, although several are propagated vegetatively.
A typical grass plant produces new leaves continuously from its growing point throughout the growing season. It also loses about the same number of older leaves through natural senescence and death. Whether growing naturally or under cultivation, turfgrasses will increase beyond the number of seeds sown. One of the objectives of good turf – grass management is to encourage that growth as quickly and as uniformly as possible.
Grasses have differing growth habits, resulting from the three different ways that they produce new shoots (Figure 13-1).
1. Rhizome-producing (rhizomatous): The shoots are produced beneath the soil’s surface and send new plants to the surface some distance out from the parent plant. The new plant develops its own root system and is independent of the parent plant, although the physical bond through the rhizome may continue.
figure 13-і. Growth habits of grasses (Delmar/Cengage Learning)
2. Stolon-producing (stoloniferous): The shoots are produced and extend outward from the parent plant along the surface of the soil, not beneath it. The new plant develops independently as in rhizome-producing plants.
3. Bunch-type: New lateral shoots termed tillers are produced from axillary buds within the leaf sheath.
Rhizomatous and stoloniferous grasses tend to reproduce more quickly and evenly than bunch-type grasses. Therefore the bunch-types require more seed and closer spacing in order to cover an area quickly and avoid clumps in the lawn.
Texture, Color, and Density
Leaf texture is mostly a measure of the width of the leaf blade: the wider the blade, the coarser the texture. Generally, the fine-textured grasses are regarded as more attractive than the coarse-textured grasses. The color of a grass and its density will also differ among species. Color variance runs the full range of greens from pastel to dark and bluish. Density refers to the number of aerial leaf shoots that a single plant or species will produce.
Seed size varies greatly among grass species. Fine-textured grasses have small seeds; coarse-textured grass seeds usually are much larger. A pound of fine-textured grass seed contains considerably more seeds than a pound of coarse-textured grass seed. A pound of fine-textured grass seed will also cover a larger area of land. For example, a pound of fine-textured Kentucky bluegrass contains approximately 2,000,000
seeds. That number of seeds will plant about 500 square feet of lawn. A pound of coarse-textured tall fescue contains about 227,000 seeds. Only 166 square feet of lawn can be planted with this particular seed. To further illustrate the differences in seed sizes, there are as many seeds in one pound of bluegrass as there are in nine pounds of ryegrass; and as many seeds in one pound of bentgrass as there are in 230 pounds of ryegrass.