Tall fescue and Kentucky bluegrass typically grow in the same regions but are quite different from one another. You can identify and differentiate these two grass varieties by the blade appearance, growth pattern, sunlight requirements, as well as a host of other features and requirements.
Tall Fescue Identification Features
Tall fescue, botanically known as Festuca arundinacea is a cool-season grass species of the Fescue genus. This perennial grass species is identifiable via the appearance of the leaf blades, the inflorescence, the seeds, the growth pattern, and how root development occurs.
The leaf blades
Tall fescue grass blades are flat, have coarse edges, tapered tips, and also feature a distinctive midrib. Meanwhile, the upper side of the leaf blades has a ribbed pattern (longitudinal venation) while the lower side has a glossy texture. Also, tall fescue leaf blades are broad (up to 0.4” wide).
Note: Tall fescue has ligules, but they’re not definitive (the ligule is a short membrane that’s barely visible).
Tall fescue grass has panicle inflorescence (seedheads) that grow to 3”-4” long and have spikelets that are about 1.5” long. The panicle branches have a rough texture, but the tip of the shoots where the panicles sprout from are smooth. Tall fescue usually flowers in the spring.
Tall fescue seeds have an oblong shape, with tapered edges. They’re tan-colored and are about 0.2” in length (about the same size as ryegrass seeds). Tall fescue grass seeds usually mature at the onset of summer.
Tall fescue has a bunch-type growth pattern, spreading mainly via vertical tillers that grow in clumps to form tight sod, though it also has short rhizomes. The bunchy growth pattern means that tall fescue fills in slowly, which is why it’s used more as pasture grass than as lawn/turf grass.
Note: For tall fescue to form new sod via rhizomes, it has to be mowed frequently.
This grass species typically grows to heights of 24”-48”. The grass height is usually determined by how fertile the soil is.
This perennial grass roots deeply (2-3 feet below the ground surface), enabling it to survive drought and extreme heat conditions.
Kentucky Bluegrass Identification
Kentucky bluegrass, scientifically referred to as Poa pratensis, is a cool-season grass species. You can readily identify this perennial turfgrass species by the appearance of the grass blades, their growth pattern, and how root development occurs.
The leaf blades
Kentucky bluegrass is easily identifiable via its boat-shaped leaf tip. This turf grass’ leaf blades are green-dark green and peak at 3”-4” inches in the spring and summer when days are longer. However, the blade length on new growth gradually reduces as the season changes to late summer and fall when days are shorter.
Combining the length of the blade and the leaf sheath, Kentucky bluegrass typically grows to a height of 18”-24” at full maturity. This type of grass also features membranous ligules at the junction of the grass blades and the sheaths. Each sheath sprouts 3-4 leaf blades.
Kentucky bluegrass has a creeping growth pattern and spreads aggressively via underground rhizomes, resulting in dense sod. They also spread via vertical-growing tillers which develop to form their own leaves.
The growth pattern of Kentucky bluegrass is also determined by the length of the day. For instance, when days are longer in late spring and summer, the shoots grow upright. Meanwhile, they assume a decumbent growth pattern when days are shorter in the fall and early spring.
Rhizomatous growth in Kentucky bluegrass occurs in two ways, both of which are responsible for this grass species’ creeping growth pattern. First, there are rhizome offshoots that branch out from other rhizomes. Then, there are shoots that sprout from the leaf axils and grow downwards, turning into rhizomes once underground.
Kentucky bluegrass roots sprout from the crowns of the above-ground shoots, from the nodes of the underground rhizomes, and from the terminal nodes of the rhizomes that grow upwards as above-ground shoots. Root growth usually peaks in the fall and in the spring when the soil temperature is at 60°F or thereabouts.
Tall Fescue vs. KBG – The Differences
Tall fescue grass and Kentucky bluegrass are both cool-season, perennial turfgrass varieties, but that’s about as far as the similarities go. There are several notable differences between these two types of turfgrass in terms of blade appearance, growth patterns, water, and fertilizer requirements, recommended growing zones, mowing needs, common diseases/tolerance, sunlight requirements, dormancy, and cost of maintenance.
Tall fescue grass blades are flat, whereas Kentucky bluegrass leaf blades are boat-shaped (concave). What’s more, while tall fescue ligules (situated at the junction of the blades and the sheaths) aren’t prominent, Kentucky bluegrass ligules are more defined and appear as hairy membranes. Finally, tall fescue leaf blades (4”-24”) grow significantly longer than Kentucky bluegrass leaf blades (3”-4”).
Tall fescue spreads primarily by way of vertical-growing tillers, whereas Kentucky bluegrass spreads primarily via underground rhizomes that grow laterally. The vertical tillers in tall fescue result in a bunchy growth pattern where the turf fills in rather slowly and has several bare spots. By contrast, Kentucky bluegrass rhizomes form thick sod that quickly grows to fill in all bare spots on the lawn.
Water and fertilizer requirements
Due to its more extensive root system, tall fescue doesn’t require as much water as Kentucky bluegrass to maintain its health and vigor. Kentucky bluegrass needs at least 2” of water every week for healthy turf growth during the growing season (summer). Tall fescue, on the other hand, requires one inch of water per week; or 1.5-inches if growing in fast-draining, sandy soil.
Moving on, Kentucky bluegrass needs more fertilizer than tall fescue once the lawn is established.
Kentucky bluegrass requires 3-6 pounds of nitrogen fertilizer per 1000 square feet every year while tall fescue only needs one pound of nitrogen per 1000 square feet in a year to maintain vigorous growth.
Though they’re both cool-season grasses suited for growth in the transition zones, tall fescue does better in warmer Southern regions compared to Kentucky bluegrass. While tall fescue will stay green during hot and dry summers in southern states like California; Kentucky bluegrass will likely wilt in such conditions.
Note: While tall fescue grows best in USDA hardiness zones 3-7, Kentucky bluegrass thrives in hardiness zones 1-3.
Tall fescue and Kentucky bluegrass have different mowing height requirements. To encourage deeper root growth and rhizome development in tall fescue, you should mow the lawn at 2”-3”. Meanwhile, for Kentucky bluegrass, the appropriate mowing height is 3”-3.5”.
Note: There are improved cultivars of tall fescue that can be safely mowed at heights as low as 1.5”.
Tall fescue boasts greater resistance to common turfgrass diseases compared to Kentucky bluegrass. The latter grass species is susceptible to several diseases including powdery mildew, Fusarium, rust, and leaf spot infections. Comparatively, tall fescue has decent disease tolerance once it matures up; only being highly vulnerable to diseases like Fusarium blight when the turf is still young.
Despite having moderate disease resistance, tall fescue turfs sometimes end up with brown patch and leaf spot infections.
Drought and heat tolerance
Tall fescue is more tolerant of drought and heat, compared to Kentucky bluegrass. Tall fescue roots grow deep into the soil (2’-3’ deep) and are thus able to draw water from deeper into the soil during periods of prolonged drought. By comparison, Kentucky bluegrass roots are significantly shallower (typically grow up to 1.5’-2’ deep), making this turfgrass species more vulnerable to drought and heat stress.
Tall fescue has better shade tolerance than Kentucky bluegrass. You can keep your tall fescue lawn thriving with just 3-4 hours of direct sunlight exposure per day. On the contrary, Kentucky bluegrass needs at least 8 hours of full sunlight per day, and will only tolerate light shade.
While both Kentucky bluegrass and tall fescue may go dormant and turn brown in the summer, they don’t do so at exactly the same time. Kentucky bluegrass is less drought-tolerant and will go dormant first, while tall fescue may not go dormant, or do so when the drought period drags too long.
Cost of maintenance
Due to Kentucky bluegrass’ higher maintenance requirements, it costs more to maintain this kind of turfgrass compared to the cost of maintaining a tall fescue lawn. First off, Kentucky bluegrass grows at a faster rate, thus needs to be mowed more frequently. What’s more, Kentucky bluegrass has a more rigorous watering and fertilizer schedule, which means you’ll spend more if you’re paying someone to take care of your turf for you.
Wear tolerance and recovery
Since tall fescue grows in tough, bunchy tufts, it’s considerably more wear tolerant than Kentucky bluegrass. However, this same trait limits tall fescue’s capacity to quickly recover from wear damage. Kentucky bluegrass, on the contrary, recovers quickly from wear damage due to its fast-spreading rhizomes.
The table below summarizes the differences between tall fescue and Kentucky bluegrass:
|Tall fescue||Kentucky bluegrass|
|Has flat grass leaf blades that can grow to 24” long||Has boat-shaped leaf blades that can grow up to 4” long|
|Has a slow growth pattern and spreads primarily via tillers||Has an aggressive growth pattern and spreads primarily via rhizomes|
|Requires less water per week and less fertilizer per year compared to Kentucky bluegrass||Requires more water per week and more fertilizer per year compared to tall fescue|
|Less susceptible to pests and lawn diseases||More susceptible to pests and lawn diseases|
|Has better wear tolerance but poorer wear recovery than Kentucky bluegrass||Has worse wear tolerance but better wear recovery compared to tall fescue|
|Has lower maintenance requirements||Has higher maintenance requirements|
Which Grass to Choose
Both Kentucky bluegrass and tall fescue have their strong points and downsides. As such, factors such as your regional climate and the intended use of the turfgrass should lead you in determining which turfgrass species between these two is the better choice for you.
Choose tall fescue if:
You’re looking to grow a pasture grass
Tall fescue is widely grown for pasture/hay used to feed livestock. Some of the reasons why this grass type is great for use as pasture is its good disease resistance and decent leaf retention in the fall. The latter reason makes it great for use as livestock food during winter.
You want to keep grass off your garden/hardscapes
While Kentucky bluegrass has an aggressive growth pattern due to its fast-spreading rhizomes, tall fescue is not a creeping grass species due to slower growth via tillers. As such, you can comfortably grow tall fescue on your lawn without having to worry about the grass creeping into your garden, patio, or driveway.
You live in a Southern State with hot summers
Many southern states experience very hot summers, with extensive periods of drought at some point during this season. Kentucky bluegrass is unlikely to survive in such dry conditions due to its shallow root system. Tall fescue, on the other hand, is better adapted to drought conditions like these due to its more extensive root system.
Choose Kentucky Bluegrass grass if:
You want a fast-spreading turfgrass species
If you’re the impatient kind and can’t withstand seeing tall fescue fill in so slowly with unsightly bare patches all over the lawn long after it was established, then Kentucky bluegrass is the way to go.
You want a sports turf
Kentucky bluegrass fills in quickly and has quick wear recovery from foot traffic stress. As such, it’s great for use on sports turfs.
Can you mix tall fescue with Kentucky bluegrass?
Tall fescue can be successfully mixed with Kentucky bluegrass to form a lawn that’s more drought/heat tolerant and also recovers faster from wear. Since tall fescue is more shade tolerant, it will thrive in the shaded portions of the lawn, while the fast-growing Kentucky bluegrass will quickly fill in bare spots on the turf.
Take note, too, that these two turfgrass species won’t choke out each other. Finally, if your lawn is Kentucky bluegrass/tall fescue blend, the appropriate mowing height is 2.5”.
- Richard L. Duble, Turfgrass Specialist, Texas Cooperative Extension: Kentucky Bluegrass Identification
- Mike Goatley, Jr. Extension Turfgrass Specialist: Identification and Management Strategies for Virginia’s Turfgrasses
- US EPA: Turfgrass and Water Efficiency