Get to Know Your Cool-Season Grasses

R. L. Rhodes
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The differences between one type of grass and another are nowhere near as stark as the differences between, say, a palm tree and a grape vine, but that doesn’t mean that all grasses respond to the same care.

“Grass is grass,” we tell ourselves, but it just ain’t so. Knowing the difference between grasses will help you better address the needs of your lawn. The place to start is with identification.

Types of turfgrass

Broadly speaking, turfgrasses can be divided into two groups, based on the climates that suit them best, tropical or temperate. The latter group is commonly known as the cool-season grasses.

Scientists can often distinguish between the two by looking at the enzymes used to carry out photosynthesis, the process of converting sunlight into the energy grass needs to grow. For the rest of us, the easiest way to distinguish between them is to pay attention to the life-cycle of the lawn. Cool-season grasses generally start growing when the soil temperature reaches about 40 to 45 degrees Fahrenheit. As such, they’re typically more active in the spring and fall, when temperatures are mild. In summer, their growth slows and the grass may turn brown as it goes dormant.

Cool-season turfgrasses are often divided into three major groups: bluegrasses, fescues and ryegrasses. When it comes to distinguishing between those different, the visible differences in structure are a more useful dividing line.

Structural elements

Image: T.Voekler & Arthur Chapman.

Left: A panicle seed head on fine fescue. Right: A spike-style seed head on perennial ryegrass.

Time to get technical. When attempting to identify cool-season varieties, there are a number of elements you’ll need to look for. To that end, some familiarity with the structure of grass is useful. From the ground up, the body of a grass plant is made up of its roots, stem, leaves and seed head.

The seed head can be helpful in identifying grass types, but usually gets lopped off when you mow your yard, so may not be available. If some portion of the grass in your yard is full-grown, you can look for differing types of seed head described as panicle, spike and receme. Panicle seed heads are like miniature trees—a central stem with the seeds, or “spikelets,” growing at the end of branches. By contrast, the spikelets on the spike type seed heads grow directly from the main stem. Raceme seed heads produce spikelets on very short branches along the main stem, but don’t worry about confusing panicle and raceme as cool-season grasses almost never produce raceme spike heads.

The leaves make up most of what we think of as turfgrass, and they can be divided into three parts: the sheath, the collar and the blade. Differences in the shape of the blades can help us distinguish between varieties. If you place a blade of grass on a flat surface, some will lie flat while others are keeled like a boat. Some are glossy underneath while others are matte. And some have a single mid-vein running down the length of the blade while others are ribbed with multiple small veins.

Image: Harry Rose/Flickr

Botanists use the word “vernation” to describe the growth and arrangement of new leaves on a plant. In cool-season grasses, vernation can be either folded or rolled. You can check the vernation of your grass by cutting a cross-section and looking at the newly formed leaves beneath the collar, or by trying to roll a shoot of grass between your fingers. If the shoot flattens, it likely has folded vernation.

Finally, we can talk about how grass plants propagate. Some use rhizomes, underground shoots that spring up elsewhere to produce new plants. Others use stolons, which are a like above-ground rhizomes that put out roots at intervals along its length. Some use neither rhizomes nor stolons, but reproduce in tufts-like bunches.

With those structural features in mind, you’ll be ready to identify different types of turfgrass.

Cool-Season Grasses

When identifying grasses, it’s a good idea to take samples from different areas of your yard, as grasses of different types sometimes grow in close proximity to one another. Refer to the table below to help identify the grasses in you find.

Type of grass Seed head Leaves Vernation Propogation
Kentucky Bluegrass Panicle Keeled, matte, mid-vein only Folded Rhizomes
Rough Bluegrass Panicle Keeled, glossy, mid-vein only Folded Stolons
Annual Ryegrass Spike Keeled, glossy, mid-vein and ribbed Rolled Bunching
Perennial Ryegrass Spike Keeled, glossy, mid-vein and ribbed Folded Bunching
Fine Fescue Panicle Keeled, matte, with few visible veins Folded Bunching or rhizomes
Tall Fescue Panicle Flat, matte, ribbed Rolled Bunching or rhizomes

If you’re unsure whether or not your grass matches, or suspect that you have a less common variety of cool-season grass, take some samples in to your nearest Extension Service office and let the experts take a look.

Once you’ve identified your cool-season grass, head to the Home Depot to buy seed or sod for overseeding or patching, as well as fertilizer for boosting the growth and health of your lawn. And keep current with the Garden Club for more articles in our series on the right lawn care for your grass type.

 

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