Called the Cadillac of lawn grasses, the ubiquitous Kentucky bluegrass (KBG) is synonymous with gorgeous and lush yards and turfs all across the northern United States. In fact, it is considered by many to be the humble pasture grass that triggered America’s obsession with lawns.
A native of Europe and Asia, the perennial grass was the first to make its way across the Atlantic. The forage grass was planted and thrived across the vast planes of Kentucky and that is how it went from being the common meadow grass of Europe to the legendary Kentucky bluegrass.
Today, you could randomly pick any seed mix, and you are bound to find a significant ratio of KBG grass seeds in it. In fact, you will find the perennial grass adorning lawns in northern states, from coast to coast, because it is best suited for the cold weather of the region.
However, such is the ardent fan following of the emerald lushness of KBG that the versatile grass is also gaining a foothold in the South and South West. This, despite the greater need for water to keep this grass standing tall in warm areas!
So, if you already have a gorgeous green swath of KBG growing outside of your home or intend to work with the widely used grass for your lawn goals, here is everything that you need to know to keep your Kentucky bluegrass lawn looking its best.
Kentucky Bluegrass is one of the most popular and widely used cool-season grasses, not only is it known for its striking deep green color but also its superlative winter-hardiness. Find out if this grass will be right for your lawn and all you’ll need to do make it thrive.
What type of grass is Kentucky bluegrass?
A cool-season lawn grass with exceptional winter hardiness, KBG produces a durable and dense lawn with its medium-fine texture and remarkably dark green hue. Depending on where you grow it and who you ask, KBG is a medium to high maintenance grass.
It has one of the longest germination times of all cool-season grasses. In fact, KBG seeds take almost thrice as long to germinate as compared to the quick-growing perennial ryegrass.
Unlike the tall fescue and ryegrasses, KBG does not grow in bunches/clumps but forms an almost even and dense carpet of green due to its lateral spread. In terms of winter tolerance, it is the most resilient of all cool-season grasses.
I’d say this is one of the prime reasons for KBG’s continued dominance in lawns and turfs all across the northern areas. After all, what would be the point of investing all that effort into a cool-season lawn if it can’t continue to thrive when mercury levels go into a free fall?
What is Kentucky bluegrass scientific name?
Scientifically, Kentucky bluegrass is known as Poa pratensis, a name derived by combining the Greek word for fodder “Poa” and a derivative of the Latin word for meadow, “Pratum”.
The majority of the seeds of the sod/mat-forming grass now come from Idaho, Washington, and Oregon although it can still be found growing widely on the verdant hills of Kentucky.
KBG is extensively used for creating lawns in yards, parks, and gardens as well as on heavily used turfs such as golf fairways, ball fields, picnic areas, and campgrounds. Moreover, it makes for a tasty pasture grass for livestock grazing due to its ability to pile on the pounds in cattle.
How to identify Kentucky bluegrass?
You won’t have much trouble identifying KBG from other cool-season grasses partly because of the extraordinary dark green color of its blades.
In fact, even without actually plucking out a blade to examine its physical characteristics, you’d still be able to spot KBG by the way it stands out from the lighter green of other grasses.
As far as distinctive traits go, I’d say that the well-defined midrib, which runs along the entire length of each blade, is possibly its most obvious and discernible trait. The midrib is flanked by parallel blade sides that taper and culminate into a boat-shaped/keeled tip.
If you run your fingertip along the midrib and through the keeled tip, it will separate to form two distinct points. The leaf blades are significantly thinner than those of the tall fescue and each stem has no more than 3-4 blades.
Because of the finer and thinner blades, KBG works well for manicured lawns as well as for more natural rolling meadows.
Is Kentucky bluegrass really blue?
There aren’t actual streaks of blue in the distinctive green of KBG. However, when compared to the lighter shades of other cool-season grasses, the deep emerald color does appear as if it has some blue mixed in it. But, that’s not how KBG got its name!
The word “blue” in the name comes from its flower heads, which are a remarkable silvery blue or purplish-blue. When a swath of KBG is seen from afar, as it flowers, it appears to be covered by a haze of blue and that is how the grass earned its moniker.
Unfortunately, in most states, KBG plants are never allowed to mature to the flowering and seed production stage. So, you can only see those flower heads in their dainty, blue glory if you ever visit northern Idaho or eastern Oregon where KBG is cultivated commercially.
Is Kentucky bluegrass a creeping grass?
Aside from some varieties of red fescue, Kentucky bluegrass is the only popular cool-season grass with a creeping growth habit.
In fact, the creeping growth habit is what gives this grass its ability to stage a rapid recovery from damage. Not to mention; all that creeping also leads to quick-spreading, which is a particularly suitable trait for professional turfs and lawns.
Creeping grasses spread through underground stems called rhizomes or through stolons, which are stems that grow above the ground.
KBG has an underground rhizomatous stem system that allows it to form a thick, self-spreading mat that can quickly cover thinning and bald spots.
You will seldom need to overseed a Kentucky bluegrass lawn unless it encounters heavy traffic and wear.
How fast does Kentucky bluegrass spread?
Let me start with the disappointing news first. It takes 14 to 21 days for the slow-starter KBG seeds to germinate.
This means that it will be a good 3-4 weeks after planting before you see the green shade making an appearance. How fast the spread is from thereon will be based on the number of seeds broadcasted.
KBG seeds are lighter so, you will need only half of what you’d go for with the fescues or the ryegrass.
Even then, I am still talking about 3 lbs/1000 sq ft. if you are laying down a new seedbed and 1.5 lbs/1000 sq ft. if you are working with a patch with fairly good growth (overseeding).
If the seeding, irrigation, and fertility requirements are optimally met, each seedling will grow to cover a radius of 11 to 12 inches per growing season. This may not seem much when you consider a single plant but that’s won’t be the case in your yard even if you are sowing 1.5 lbs/1000sq ft.
So, you can expect your lawn to fill out within one season.
The best Kentucky bluegrass varieties
Well over 100 Kentucky bluegrass cultivars have been introduced in the market over the last two decades. Of these, a mere 3 were pasture varieties while the rest were all meant for lawn application.
Generally, cool-season grass cultivars can be segregated into two categories:
- Common or old varieties: These are the original cultivars that look gorgeous and have many favorable traits, but they are susceptible to fungal diseases and have a lower tolerance for both heat and shade. These common cultivars are often found in generic seed mixes.
- Improved/hybrid varieties: As their name suggests, these cultivars were specifically bred by combining the original variety with local bluegrasses (for example, Texas bluegrass) to yield hybrids that perform better when subjected to drought, heat, shade and wear.
The problem is that you won’t find these at the local garden store. They are usually only sold by specialty establishments that serve the turf and landscaping industries. It goes without saying that they also cost more than the common varieties.
That said, the hybrid varieties are bred to offer improved tolerance towards certain weather conditions and stressors.
I won’t give you the complete list of all Kentucky bluegrass cultivars but some that may suit specific lawn management goals are:
- Better heat tolerance: Midnight, Victa, Vantage, Baron adapt well to southern climates as compared to other cultivars.
- Improved shade tolerance: Opt for Bristol, Touchdown, Nugget and Glade if you have a significant amount of tree foliage cover.
- Exceptional drought tolerance: In a study conducted by the University of Arkansas, the cultivars, Moonlight, Diva and Prosperity showed the highest tolerance for drought.
- Grow well even after a close mowing: Bristol, Touchdown, Ram 1 and Adelphi have the greatest tolerance to close mowing.
If you buy a seed mix, you will likely end up with a combination of cool-season grasses. Although exclusive KBG lawns are not as common now as they used to be 4 -5 decades ago, you can still find KBG-only seed mixes.
The thing to remember when buying single-variety seeds or KBG seed mixes is that the more diverse the blend of cultivars the greater will be their resilience to adverse factors.
Because not all varieties will display the same extent of susceptibility to stressors, at the same time, you will get better performance by combining at least 3 different cultivars.
When to plant Kentucky bluegrass?
This is a cool-season grass, so summer is definitely out. Spring is the second-best season but KBG seeding in spring should only be done if absolutely needed. Ideally, as with its competitors, KBG fares particularly well when planted in fall.
- Seeding in fall: Wait till temperatures reach a range of 50 to 65 degrees F to broadcast the seeds. This will give the seeds the right moisture level to germinate and will provide ample time to the seedlings to mature enough to get through winter. Ideally, schedule the seeding sometime between mid-September and late October.
- Dormant seeding: Many experts consider this to be an effective pre-spring seeding technique that helps to deal with most of the issues that you are likely to encounter during spring seeding. Dormant seeding is done before the ground thaws. So, you don’t have to deal with overly moist or soft soil, which can be hard to work with.
Moreover, the effort required is less because the ground naturally cracks and heaves as it thaws, making room for the seeds to slip deeper into the soil layers. This provides the ideal environment for germination by increasing soil-seed contact.
- Seeding in spring: With KBG, spring seeding is rarely successful. So, if you must overseed, combine KBG with other cool-season grasses for best results. As far as spring seeding goes, the earlier you start the better because KBG does take longer to germinate and establish. So, you have to make sure that the seedlings get enough time to mature before the summer heat takes over. Plus, keep an eye out for crabgrass if you have planted KBG in spring.
With that out of the way, let me clarify that spring seeding should only be attempted if the turf has been damaged due to winter weather or if it has not recovered as well as it should have from the problems of the previous year or if you are reclaiming a lawn after new construction.
What temperature does Kentucky bluegrass grow best?
Let me start at the roots; with Kentucky bluegrass, you get the greatest root growth in fall followed by spring. Peak growth is reached when soil temperature hits 60 degrees Fahrenheit. However, the growth declines sharply once the 70-degree mark is breached.
Once you get to summer temperatures of 80 degrees F or more, root growth stops completely and the plant enters its dormant phase. Like all cool-season grasses, new shoots develop in fall and spring. If planted in the transition zone, new leaves appear all year round.
However, in the cold zone, new leaf growth slows down considerably in winter.
Spring provides the optimal temperature for leaf growth, with a spacing of just 10 days between the appearances of new leaves. This slows down to 22 days between appearances as temperatures rise, eventually leading to dormancy in summer. Growth picks up again in autumn, starting at 22 days between new leaves.
Does Kentucky bluegrass need a lot of water?
Proper water management is a crucial aspect of KBG lawn care. This grass is always in need of a drink because its shallow root system does a poor job of holding on to moisture. Plus, the root system is simply not equipped to dig deeper into the soil layers to access the stored moisture there.
So, yes, Kentucky bluegrass does have greater irrigation requirements than other cool-season grasses. For instance, even when the weather is normal, you would still need twice as much water for KBG as you would for other cool-season grasses.
Generally, with other cool-season lawns, you are looking at an average weekly irrigation requirement of 1-1.5 inches, which can easily be supplied in a single session.
With Kentucky bluegrass, you would have to supply 1.5 to 2 inches of water even in normal weather conditions.
The irrigation requirement goes up in summer for all grasses. But, once again KBG demands nearly 2.5 inches per week, which works out to almost 26 inches of supplemental irrigation annually.
Compare this with the mere 10 inches of additional/external irrigation required by other cool-season turfs. Now, you know why KBG is called a high maintenance grass. Actually, apart from its greater need for water, this grass has pretty standard maintenance requirements.
How often to water Kentucky bluegrass?
Typically, you will need to irrigate with at least 1.5-2 inches of water every week in normal (non-summer) weather conditions. When things get hot in the transition zone, you will have to increase irrigation to 2.5 inches of water per week.
Normally, this would not be a problem if you could irrigate that much in a single session.
But the shallow root system will rapidly lose moisture within 24-36 hours. So, you will have to supply the h2o in 2-3 sessions of no less than 1 inch each, spaced about 2-3 days apart. Basically, you are talking about watering the lawn twice or thrice a week.
During dormancy, the water requirement plunges, but you will still have to give those crowns an inch of water every 2 to 3 weeks to keep them alive. This way, you are keeping them alive, so that they can recover when weather conditions improve or irrigation requirements are fully met.
Kentucky bluegrass drought tolerance
You will find a lot of contrasting views when it comes to the drought tolerance of KBG. Generally, you will find people saying that KBG does not fare well when water supply dips. What I like to do is base my conclusion on relevant studies. So, here’s what tests have revealed over the years:
- In a study conducted in Utah, KBG lived for an impressive 120 days in drought conditions, easily outperforming other cool-season grasses as well as some warm-season grasses.
- Similar results were observed in an early British study conducted in 1943. The researchers concluded that KBG had the highest drought resistance when the soil moisture plunged down to a mere 3%.
- Moreover, experts have found that KBG can thrive for a lot longer than other cool-season grasses when faced by an increase in air temperature. However, it has a lower tolerance for an increase in soil temperature.
Plus, there is a significant difference in the drought tolerance of various cultivars. In addition to the ones that I have already mentioned above, varieties such as Apollo, Showcase, Unique and Brilliant also exhibit impressive drought resistance.
How high should you mow Kentucky bluegrass?
When you are watering or mowing your KBG lawn, the one thing to remember is that all maintenance efforts are influenced by the shallow root system of this grass. Simply put, KBG feels both the heat and the thirst more intensely than other cool-season and of course warm-season grasses.
So, here is what the mowing requirements look like:
Normal weather mowing: A warm-season grass like Bermuda grass will thrive even when mowed to 1 inch. Perennial ryegrass will grow well even if cut to 1.5-2 inches. But, you have to necessarily keep above 2 inches for Kentucky bluegrass. And that’s the requirement for non-summer months!
Summer mowing: Once the mercury starts soaring, so should your mowing height. Go for 3-4 inches to give those fine blades of Kentucky bluegrass better heat and drought tolerance in summer and in low rainfall/dry conditions.
For initial mowing: With young seedlings, wait till the blades reach a height of 2.5 inches to start mowing. But remember to not go below 2 inches. You can use either a reel or rotary type mower but make sure that the blades are sharp and that the reels are adjusted properly.
The shallow root system also means that not just the young seedlings but also mature plants get pulled out easily if you are not careful.
For regular mowing: To achieve a mowing height of 2 inches, make sure that you take off the length before it reaches 3 inches. Usually, weekly mowing will be enough to achieve this result.
When mowing, never take off more than one-third of the leaf length in a single session as this will stress the plant.
If the grass grows taller than the required height, mow down to the appropriate length over subsequent sessions instead of taking off the entire height at one go.
Although 2 inches is the ideal mowing height for Kentucky bluegrass, cultivars such as Touchdown, Ram1 and Flyking can be mowed down to 1 inch. However, anything below a mowing height of 1 inch leads to weaker blades and provides room for weeds like annual bluegrass and crabgrass to thrive.
In contrast, you won’t have such a big problem with weeds if you keep the mowing length above 1-1.5 inches.
Will Kentucky bluegrass choke out weeds?
An established KBG lawn will be dense enough to choke out weeds. Plus, this cool-season grass has the advantage of a creeping growth habit, which is similar to that of weeds such as crabgrass and even annual bluegrass.
In fact, a well-established and well-taken-care-of KBG lawn will quickly bounce back from a weed invasion and will come back from all directions to reclaim its territory. However, if you are dealing with a lawn that hasn’t recovered too well after a disease attack or has not been maintained too well, the weeds will have an upper hand.
Ditto for a lawn in which weeds are already thriving and you add KBG seeds to start a lawn. The slow vigor of the KBG seeds and seedlings means that they will be no match to the aggressive weeds. So, they will in all likelihood be starved to death by the weeds.
Without a doubt, established KBG will perform much better when faced with a weed threat than other cold season grasses with bunch-growing habits. But, you will need to give KBG time to establish its dominance. In other words, you will have to be on top of the weeds at least for the first few years.
And that is all you need to know to have an impressive pure or mixed KBG lawn! Aesthetically pleasing and durable, this grass performs beautifully on its own and works well with other cold season grasses, making up for their deficits with its winter-hardiness.
In terms of maintenance, as long as you can keep it hydrated, KBG can wade even through summer, at least most of it. Moreover, it is nearly as wear-resistant as the ryegrasses and the tall fescue. Plus, it is hard to not be enticed by that green, which is like no other.
Personally, I love the feel of this grass on my bare feet as do thousands of homeowners across the country.
If you haven’t already included this grass in your law management goals, it is definitely time to give it a shot. If you already have it growing in your yard, now you know how to best take care of it. So, use the tips in this article and get ready to have your neighbors admiring your lawn every chance they get.