Spring has arrived. Signaled by the swooping robins, honking geese, and bustling aisles in the garden centers. A popular spring task is selecting grass seed to help plump up the lawn for the growing season. But what cool-season grass seed should you pick for your yard?

Timing

The garden center shelves are bursting with bags of lawn seed, but is it the right time to sow that seed? It doesn’t hurt to overseed in the spring but there are a few reasons why to wait until late summer to early fall.

• The soil is cold, so germination is not optimum
• We’re going into summer, a stressful time for a cool-season lawn
• Predation of seed from wildlife is higher coming out of winter

I often say sod in the spring and seed in the fall, but maybe you have some damaged areas to fix or want to fill in a thin lawn. Following are different types of cool-season turf and their ideal uses whether you’re seeding in the spring or fall.

Kentucky bluegrass

A staple species of turfgrass that has been around for generations. Kentucky bluegrass is used in fair to high-quality lawns. An advantage of this species is its ability to recover from damage. Bare spots in the lawn will over time fill back in as this grass spreads via underground rhizomes. Kentucky bluegrass also has a good drought defense. When the summer gets hot and dry, this grass will go dormant to protect the plant so when cooler temperatures and rains return, it will green back up. A drawback of Kentucky bluegrass is its poor germination rate compared to other lawn species, making it slow to establish from seed. Kentucky bluegrass grows best in a full sun lawn.

Perennial ryegrass

Another classic species, perennial ryegrass has often been mixed with Kentucky bluegrass because their texture and color are very similar. Perennial rye compliments Kentucky bluegrass because it has a very good germination rate. Perennial rye is a bunch grower which means it will not spread via runners to fill in bare spots. It is also fairly short-lived, allowing the longer-lived Kentucky bluegrass to eventually take over. I often recommend those needing to fill in a bare spot quickly to seed with perennial rye but to return in the late summer to early fall and seed a longer-lived species. Perennial ryegrass will tolerate partial sun but will grow best in full sun.

Turf-Type Tall Fescue

Once a grassy weed, plant breeders have turned this species into a reputable turfgrass. Turf-type tall fescue has been bred from tall fescue to have a finer texture and better green color that is similar to Kentucky bluegrass. Turf-type tall fescue (often shortened to tall fescue) has a more extensive root system that allows this plant to extract more water from the soil, which means it is less reliant on irrigation systems. Like perennial rye, tall fescue has a bunching growth habit, so it will not spread overtime to fill in bare spots. However, its drought tolerance and resilience have propelled this grass to be very popular in the turf industry. Tall fescue can tolerate some shade, but it still needs at least four hours of direct sunlight each day.

Fine Fescue

When looking at a bag of turf seed, you may not see the name “fine fescue”, but this is a term used to describe a group of grass species. Common fine fescue species include creeping red fescue, chewings fescue, hard fescue, and sheep fescue. True to its name, fine fescue has a texture that gives it a wispy appearance. Often included in no-mow turf seed mixtures, fine fescue works well in low maintenance areas. For those fighting shade in their yard, fine fescue species are recommended as the most shade tolerant. This species still requires at least 2 hours of direct sun per day to grow a fair stand of grass. There isn’t a species of grass that works well in deep shade. For those situations install landscape beds or embrace natural groundcovers such as violets or moss.

Annual Ryegrass

Beware of seed bags that list annual ryegrass as the primary species. Annual rye is not long-lived and only considered a temporary groundcover. What annual rye offers is a quick germination rate. Many of those with a warm-season lawn in the southern and western United States, will overseed with annual rye in the fall to keep the lawn green over the winter months. This strategy isn’t very effective in Illinois where we grow predominately cool-season grasses. However, it is easy to find these products on garden center shelves in Illinois. Homeowners may sow this seed and cultivate an established turf, only to have the entire lawn dead the following year. Annual rye is recommended for overseeding warm-season lawns for winter color or for erosion control where a quick groundcover is needed to stabilize soils.

There is a lot more when it comes to selecting a lawn species. For more resources, check out the following websites:

• University of Illinois Extension LawnTalk
• National Turfgrass Evaluation Program 
• Home, Yard, and Garden – Reading a grass seed label 

Good Growing Tip of the Week: Got a few bare spots in the lawn to repair? Try mixing your lawn seed with a 50/50 mix of compost and topsoil. Rake up the bare spot and spread the seed and soil mixture. Firm up the soil and water. Watch the process for turf patch repair in detail by Cornell University turfgrass.

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MEET THE AUTHOR

Chris Enroth is a horticulture educator with University of Illinois Extension, serving Henderson, McDonough, Knox, and Warren counties since 2012. Chris provides horticulture programming with an emphasis on the home gardener, landscape maintenance personnel, and commercial landscapers. Additional responsibilities include coordinating local county Master Gardener and Master Naturalist volunteers - providing their training, continuing education, advanced training, seasonal events, and organizing community outreach programs for horticulture and conservation assistance/education. In his spare time, Chris enjoys the outdoors, lounging in the garden among the flowers (weeds to most).