Know Your California Turf for the California Supplemental Exam

Turf is a common design element in many California landscape designs. Landscape architects can specify many kinds of turfgrass for their projects. Picking the right grass can ensure a successful project while the wrong grass and be an absolute failure. Let’s review California’s most common turfgrasses.

Common Turfgrass Species for California

• Bermudagrass (common and hybrid)—Cynodon spp.
• Kentucky bluegrass—Poa pratensis
• Perennial ryegrass—Lolium perenne
• St. Augustinegrass—Stenotaphrum secundatum
• Tall fescue—Festuca arundinacea
• Zoysiagrass—Zoysia spp.

Warm-Season Versus Cool Season

Turfgrasses are classified as either warm-season or cool-season.

Warm-season lawns grow vigorously during the hottest months and are dormant in winter. In summer, the lawn looks rich and verdant. In winter, the grass turns tan because the top growth goes dormant. Warm-season can be overseeded with annual turfgrass seed in autumn so that the lawn has year-round green color. Zoysiagrass, St. Augustine, and Bermudagrass are all warm-season turfgrasses.

Cool-season grasses grow best in spring and fall and are dormant or semi-dormant during the hottest part of the summer. With adequate water, cool-season grass can stay green in summer even if it is dormant. Tall fescue, perennial ryegrass, and Kentucky bluegrass are cool-season turfgrasses.

Right Grass, Right Place

All of these grasses perform well in California under the right conditions.

Sun

Most grasses require at least six to eight hours of direct sun to thrive. But, some grass species can tolerate some shade and still look acceptable in the landscape.

These turf species are listed in order of shade tolerance.

1. Red fescue (Festuca rubra)
2. St. Augustinegrass
3. Zoysiagrass
4. Tall Fescue
5. Kentucky Bluegrass
6. Perennial ryegrass
7. Bermudagrass

Red fescue and St. Agustinegrass are the most shade tolerant turfgrass species. Bermudagrass is the least shade tolerant and looks very poor in shade.

Water Use

Cool season turf requires more irrigation than warm-season turfgrass. According to the Water Use Classification of Landscape Species (WUCOLS), cool-season turf requires 90 percent of a site’s reference evapotranspiration rate (ETo). On the other hand, warm-season turf only requires 70 percent of ETo. Therefore, warm-season turf uses less water than cool-season turf.

Some grasses naturally resist drought better than other species. The most drought grasses are on top of the list while the thirstiest species hover at the bottom.

1. Hybrid bermudagrass
2. Zoysiagrass
3. Common bermudagrass
4. St. Augustinegrass
5. Tall fescue
6. Kentucky bluegrass
7. Perennial ryegrass

Heat Tolerance

Warm-season turfgrass is more heat than cool-season turfgrass. This list arranges turf species by heat tolerance with the most heat-tolerant species at the top of the list.

1. Zoysiagrass
2. Bermudagrass
3. St. Augustinegrass
4. Tall fescue
5. Kentucky bluegrass
6. Perennial ryegrass

Turf Texture

Leaf texture may be an important design factor for a particular project. Turfgrass with wider leaf blades create a coarser texture. Narrow-leaved turfgrass species add a fine-textured look to the landscape. Here is a list of turfgrass varieties order from coarsest to finest texture.

1. St. Augustinegrass
2. Zoysiagrass
3. Tall fescue
4. Common bermudagrass
5. Kentucky bluegrass
6. Perennial ryegrass
7. Hybrid bermudagrass
8. Red fescue

The Bottom Line

Turfgrass is a useful plant in the landscape. A well-maintained lawn is great playing surface for pets and children. Many athletes strongly prefer real turf over modern artificial turf substitutes. While turf does consume lots of water, proper species selection and efficient irrigation can reduce turfgrasses environmental impact.

Be prepared to answer a question or two about turfgrass selection or irrigation on the California Supplemental Exam for landscape architects.