Everything About Kentucky Bluegrass
Kentucky bluegrass is beautiful to look at and also pleasurable to walk upon barefoot. With favorable growing conditions and necessary care, it produces a lush and durable lawn in rich emerald to blue-green color and medium to fine texture.
No wonder it’s a preferred lawn grass in the northern region of the United States.
Published: October 21, 2022.
What is Kentucky Bluegrass?
Kentucky bluegrass (Poa pratensis), often referred to by its initials, KBG, is a cold-season grass that is extremely winter hardy. Its winter hardiness is the highest among all the common cool-season lawn grasses. Its water requirements are moderate. However, if it undergoes heat and drought conditions for a prolonged time, it will go dormant.
Although it’s named so, and the state of Kentucky is called the ‘Bluegrass State’, Kentucky bluegrass didn’t originate in Kentucky, but in northern Asia and Europe just like many other lawn types of grass used in the United States.
However, Kentucky bluegrass and other Poa grasses do well in Kentucky’s climate and cover the smoothly rolling hills of the state.
As mentioned earlier, KBG is a cool-season grass which means that its growth is the most vigorous during the cool seasons of fall and spring. It’s a perennial grass which means that it returns year after year.
It’s well suited to the northern parts of the US where it gets its natural preferences like moderately warm summers and cold winter.
Kentucky Bluegrass grows 18 to 24 inches tall and has a boat-shaped leaf tip.
Since Kentucky bluegrass has shallow roots, it’s not very tolerant to heat and drought. This has restricted its use towards the south where there is higher heat and humidity favorable to warm-season grasses like St. Augustine and zoysia grass.
KBG spreads quickly with underground stems (rhizomes) and forms a dense lawn. This vigorous growth habit offers KBG the ability to recover quickly from damage. New shoots form mainly in the spring and late summer. Most of them formed in the spring remain vegetative, while those formed in late summer usually terminate in an inflorescence the next spring.
Its growth significantly retards in hot summer months and if the heat is extreme it’ll go dormant. However, it recovers soon with the return of normal conditions.
Although Kentucky bluegrass prefers full sun, some of its varieties can tolerate light shade.
According to some experts, it’s good to create a turf of 85% of Kentucky bluegrass and 15% perennial ryegrass. Such a lawn is more disease-resistant and heat-tolerant than Kentucky bluegrass alone.
Growing Zones
Kentucky bluegrass performs well in the USDA plant hardiness zones 3 to 9. As mentioned earlier, it’s well-suited to the northern parts of the United States where moderately warm summers and cold winters favor its growth.
In the southern United States, KBG is limited to the transition zone from North Carolina through most of Tennessee and northern Arkansas to the Texas panhandle and Oklahoma.
It’s also grown all over the East Coast. In the western states, it can be grown with extensive watering.
Kentucky Bluegrass Varieties
Kentucky bluegrass is one of the many species of bluegrass, others being Rough Bluegrass, Annual Bluegrass, and more.
Further, it’s divided into ‘types’ such as Compact, Compact Midnight, Compact America, Aggressive (High Density), Mid-Atlantic, CELA (Challenger, Eclipse, Liberty, Adelphi), BVMG (Baron, Victa, Merit, Gnome), and more. These are further divided into varieties like:
Compact: Amazon, Apex, Bewitched, Blueberry, Goldstar, Hampton, Skye, Prosperity, Platini and more
Compact Midnight: Absolute, Midnight & Midnight II, Tsunami, 4-Season, Awesome, Award, Rugby II and more
Compact America: Mystere, Langara, Mallard, Unique, Mystique, Brilliant, Boutique, Apollo, Bedazzled, Sonoma and more
High Density: Plush, Zinfandel, Cabernet, Aura, Livingston, Monopoly
Mid-Atlantic: Eagleton, Preakness, Plush, Wabash, SR 2000, Monopoly, Bel-21
CELA: Challenger, Liberty, Jefferson, Eclipse, Adelphi
BVMG: Baron, Clearwater, Crest, Dragon, Fortuna, Abbey, Goldrush, Envicta, Cannon, Nassau, Merit, and more.
Each of these varieties has its own qualities and characteristics such as good heat tolerance, very dark green color, finer leaf, higher density, aggressive growth, wear tolerance, excellent winter color, and so on.
It’s advisable to contact one’s local extension office or seed sellers to know which KBG varieties are best for their location.
Other Bluegrass Varieties
Rough Bluegrass
This is used in damp, shaded areas. It doesn’t do well in full sun or in arid spaces, except when used in winter to overseed dormant Bermuda grass.
Annual Bluegrass
This is a grassy weed with a life cycle of one year. It’s a “winter annual” which means that it sprouts and matures in the fall, lives through the winter, produces seeds in the spring, and then dies. It’s one of the first grasses to green up with the arrival of the spring.
When to Plant?
The best time to plant Kentucky bluegrass is fall which is roughly around mid-September through 1st November when soil temperatures are around 50 to 65 degrees F.
Fall planting help seedlings establish by the onset of winter. It also helps the KBG lawn to be in place for the quickest spring growth. Kentucky bluegrass seeds need the soil temperature to be warm enough for sprouting and root building for winter survival.
Another option is to seed KBG in late winter or early spring.
How to Grow Kentucky Bluegrass?
Kentucky bluegrass can be grown from seed or sod. All the other steps for both are the same, except the steps of seeding and sodding.
As mentioned earlier, the ideal time to plant KBG seed or sod is fall when soil temperatures range from 50 to 65 degrees.
This offers time for seedlings to establish themselves by the start of winter. One can choose only one variant or multiple variants of KBG that will spread across their entire space.
The benefit of planting various variants is that the lawn will have genetic diversity due to which the lawn can overcome particular issues of the area. These issues include pests and diseases that may ruin the lawn.
Check Your Location, Weather, Soil, and Seed
The grower should first make sure that their location, weather, and soil are suitable for Kentucky bluegrass.
Also, they should make sure they want a single variety or a mixture, and if the seed they have chosen will develop into the type of grass they want.
Measuring the Area and Checking its Adaptability
The grower should measure and record the area of their lawn. It should also be noted that different turf grasses tend to handle the different aspects of the site in unique ways.
Thus a site suitable to some grass types may not be very suitable to others. So, the gardeners should find out which of their areas is suitable for Kentucky bluegrass.
Testing the Soil
Growers should get their soil tested for nutrients and deficiencies so they can apply appropriate fertilizers and make other amendments. Amendments should be applied before tilling so they will be uniformly incorporated.
Fertilizers should be applied after tilling but before raking/dragging the soil to level it. They can even be applied right after planting just in the seeded areas. Over-fertilizing is not advisable for the fall-seeded lawn because nitrogen can make the grass vulnerable to winter kill.
Eliminating Weeds
Before starting the plantation of KBG, one should eliminate the existing grass and weeds in their yard. They can do this with non-selective weed control.
This should be done well ahead of actual seeding because one should wait for around 2 weeks after spraying before seeding.
Growers should read the label on the product to know the exact length of time they should wait for before seeding. Planting too early could injure or kill seedlings by the residues of the chemicals.
Otherwise, one can even just till the existing grasses and weeds without killing them with chemicals.
Preparing the Soil
Kentucky bluegrass needs well-drained, well-prepared soil. Tilling and aerating the soil are the best ways to prepare it for KBG planting. The gardener can buy or rent a rototiller and rototill their entire yard first lengthwise and then widthwise.
If they don’t prefer tilling, they can cultivate their area with a shovel, garden rake, or hoe.
Then the gardener should water the tilled soil, preferably for around 1 month if time permits, and wait if any new weeds sprout. If they do, the gardener should spray them before seeding.
Soil Amendment
The gardener should then till in organic matter such as compost, destroyed yard waste (such as grass clippings, leaves, etc.), or rotted manure to the upper 8-10 inches of the soil. This will improve the structure and fertility of the soil.
This grass needs well-drained soil with a pH between 6.0 and 7.0.
Seeding
2 to 3 pounds of seed are needed per 1,000 square feet. The gardener should rake the area to make the soil surface as smooth as possible.
They should measure the quantity of seed required for the lawn into separate containers or buckets. They should make sure they avoid using more seed than the recommended quantity. An overpopulation of seedlings will deteriorate individual plants, cause growth problems and make the lawn vulnerable to pests and diseases.
The gardener can sow seed by hand or with a broadcast spreader. If they use a spreader, they should sow one half of the seed lengthwise and one half crosswise so as to avoid any skips.
After this, they should rake the area lightly to cover the seed with not more than 0.25 inches of soil.
It’s a good idea to cover the area with wheat straw. This will prevent erosion and washing while the seed is sprouting. Around one bale of wheat straw per 1,000 square feet is enough. The gardener should never use hay because it contains weed seeds.
Sodding
Growers should do all the steps as described above even for sodding. Most importantly they should perform the step of leveling the ground.
As growers measure their area, they should buy enough square footage of sod to cover the entire area completely.
Growers should preferably lay the sod right after they are delivered. If the grower plans to wait for a couple of days, they should unstick the pallet and keep the blocks spread. If they keep the sod stacked, the sod will soon turn yellow.
Before laying the sod, the gardener should make sure they water the ground, but should not make it wet. They should then lay sod lengthwise beginning at the top of the ground. This will make the longer side of each piece of sod run across instead of down.
The pieces should be laid in a brick pattern and not in a checkerboard pattern. Each piece should be worked tight against its adjacent pieces to prevent the borders from browning and rut formation.
The grower should pound each piece of sod with their palm to fix it into the soil below and to remove any air pockets.
Watering
Whether the gardener has used seed or sod to establish their KBG lawn, they should properly irrigate the area in the coming few weeks.
A newly seeded or sodded lawn should be kept moist for around 2 weeks. Gardeners should water lightly, but frequently. If the surface becomes soupy or gets eroded, they should skip a watering. If the soil surface dries out more quickly, they should water more often.
After a couple of weeks, the frequency should be reduced but the amount of water should be increased.
By 4-6 weeks, when the bluegrass lawn is established, it will need around an inch of water per week whether by irrigation or rainfall.
Fertilizers
A KBG lawn seeded in the fall may benefit from a light application of soluble fertilizer in mid-winter. The gardener should use a 3-1-2 fertilizer that should not contain slow-release nitrogen.
During its active growth period, KBG will need 4 to 6 pounds of nitrogen per 1,000 square feet.
Mowing
Kentucky bluegrass should not be mown more than 1/3 of the blade height in a single mowing session. The height of the blade should be from 1 ½ to 3 inches.
If the gardener mows lower than this, weeds are encouraged. High mowing promotes deeper rooting and higher heat and drought tolerance.
Taking Care of Kentucky Bluegrass
Watering
Mature lawns should be given occasional yet deep watering, around every 5 to 7 days to help them develop a healthy, extensive root system. Watering too often will cause shallow roots and a weaker lawn.
Ideally, the grower should water early in the morning to reduce evaporation. If the weather is hot and humid, they should avoid watering in the evening as it can cause diseases.
Water requirements may differ from lawn to lawn because of soil structures, terrain, etc. To practice responsible water usage, one should learn to identify signs of dry lawn grass.
Grass that needs water will show a gray tinge, instead of its usual blue-green color. The blades too may contract and take a pine-needle shape. In that case, the gardener should water the lawn immediately. It’s therefore advisable to check the lawn often as it will indicate the water requirements of the lawn and help avoid over- or under-watering.
Mowing
In cooler times of the year, the grower can mow Kentucky bluegrass as low as 1 ½ inch. However, in summer they should mow it to 3 to 4 inches to help the grass survive the summer heat.
Some gardeners hardly adjust the mower below 4 inches across the year. Though this may seem high, the grass soon adjusts. The extra blade length helps the grass endure heavy traffic and drought.
Fertilizers
The grower should apply fertilizers to their Kentucky bluegrass lawn 3 to 4 times per year. The schedule of fertilizer application should be like this:
- In the first half of September month, balanced fertilizer like 12-12-12 at the suggested rate
- In the first half of November, a high-nitrogen fertilizer like 32-3-8 (preferably partial slow-release nitrogen) at 1 times the suggested rate; this is the most important fertilizer application for root development
- In the first half of April, a combination of fertilizer and crabgrass control products; these should not be applied more than the suggested
- In the latter half of May, a balanced, slow-release fertilizer if required for color; this is the best period to apply an organic, non-burning product made from non-processed animal manure
Growers should better apply fertilizer with a rotary-type spreader for best outcomes. They should apply it in two different directions to keep it from streaking. After applying the fertilizer, the gardener should immediately water the lawn.
Weed Control
The grower should apply crabgrass pre-emergent control as suggested above in the fertilizer application schedule. Granular or sprayable products can be used for broadleaf weeds such as thistle, ivy, dandelion, clover etc. They should apply granular products in the morning when dew is present on the grass. Sprayable products are best used when weed pressure is infrequent.
The gardener can even spot-spray grassy weeds, but these weeds generally need different products than that for broadleaf weeds. Spot-spraying should be done carefully to avoid damage to the lawn. When temperatures rise above 90°F, the grower should avoid herbicides.
Pests and Diseases
Insects: Kentucky bluegrass may be attacked by insects like sod webworms, leafhoppers, billbugs, and white grubs.
Growers can apply white grub controls as a preventative measure. They can get products that only kill insects that harm the grass and not the beneficial ones. The products can be applied as soon as damage is noticed.
Since damage can take place quickly, it’s important to watch for insects or remember the period when they’re active. Products containing imidacloprid as an active ingredient are useful against white grubs and should be applied from 15th June to 15th July. Gardeners should make sure to water in after the insecticide application.
Diseases: There are three most common diseases that affect Kentucky bluegrass. They are “Rust”, “Melting Out Disease” and “Leaf Spot”. Growers can control them by correct irrigation techniques and occasional use of high-nitrogen fertilizers. Rust problems normally indicate low-nitrogen soils. A small amount of nitrogen fertilizers can solve the problem.
Another serious disease is Necrotic Ring Spot. It occurs on heavily fertilized bluegrass. It’s tough to control once established. Growers should apply fungicide treatments. They should consult their local garden center for products.
Growers can follow preventative maintenance with core aeration to get rid of soil compaction and to control thatch. Just like with all grasses, for KBG too it’s very helpful for the gardener to know about the use of organics to develop beneficial microorganisms which are natural enemies of disease-causing pathogens.
With correct watering and fertilizer application practices, the gardener should experience a reduction in diseases. Still, if diseases do occur, the gardener should first check the watering schedule and avoid evening waterings.
Although a Kentucky bluegrass lawn needs slightly high maintenance, it gives results that make the gardener proud. Thus if the gardener lives in the north or any climate that is favorable for the Kentucky bluegrass, they must try growing this soft and gorgeous-looking lawn!