Ultimate Guide: Perennial Ryegrass

perennial ryegrass guide

A fine, velvety texture, the most gorgeous green color and blades that literally reflect sunlight and gleam all day long even when the mercury goes for a plunge, that is perennial ryegrass for you. Is it any wonder then that what was once a humble forage grass is now the darling of lawn care experts and homeowners across the country?

Although it is a cold season grass, it is widely used in both southern and northern applications across all three zones. Why you wonder? Well, because this is a rapid-growing grass and by that I mean, you can expect germination in as little as 3 days.

In fact, few other options offer the fantastic results that perennial ryegrass can provide for immediate and long-term lawn goals. Moreover, this hardy grass can take heavy footfall in its stride and still stand tall and green. This is not to say that perennial ryegrass is devoid of drawbacks.

But, if you know the pros and cons of working with this grass, you can turn it into your secret weapon for a lawn that leaves onlookers utterly impressed. So, here is my ultimate guide to perennial ryegrass that will give you all the information you need.

Perennial ryegrass offers speed, resilience, and color, which explains its almost ubiquitous presence in seed mixes. If you haven’t already used this cool-season grass in your lawn, you definitely should as a lush green perennial ryegrass lawn is a great looking lawn.

Is perennial ryegrass good for lawns?

The cool-season grass is the main species to grace the Wimbledon Tennis Club as well as the August national Golf Club. So, in terms of aesthetics, you definitely have a champion on your hands. However, its presence on professional turfs also tells you that this grass calls for a significant amount of maintenance.

This is one of the reasons this grass is seldom used on its own, despite its impressive characteristics. Also, perennial ryegrass is a supportive grass that provides protection and shade to the seedling of slow-growing grasses like the Kentucky bluegrass.

In fact, when combined with the tall fescue or with Kentucky bluegrass for a lawn in the temperate zones, these grasses do a fantastic job of rounding the characteristics of each other to yield a lush, rich lawn.

Also, perennial ryegrass remains one of the best choices when you need to reclaim a construction site or want to stop soil erosion on the double.

Check out my ultimate guides for different varieties of grass.

What is perennial ryegrass used for?

Fix bald spots: Because this cold season grass can go from seed to grass that can be mowed in as little as 21 days, it is frequently used to fill bald spots. Moreover, it is a resilient species that has been bred to resist pests and diseases. So, it is also used for overseeding lawns that have suffered visibly from these problems.

Make up for the slow growth of other grasses: Although perennial ryegrass isn’t as cold-resistant as the tall fescue or Kentucky bluegrass, it is used to make up for the three-week-long starting time of Kentucky bluegrass in cold season lawns.

In fact, the makers of seed mixes know that homeowners are all about instant gratification and will delight in the quick growth of perennial ryegrass. This is also one of the reasons to include it in seed mixes.

For greenery all the way: When it comes to warm-season lawns, perennial ryegrass is frequently combined with Bermuda grass. This helps to have yearlong lush greenery in the yard because as the Bermuda grass goes dormant in winter, perennial ryegrass takes over and continues to make the yard shine even in the dead of winter.

To fill out thinning: Perennial ryegrass does exceptionally well in areas with moderate summer and winter weather. This has contributed largely to its popularity in the Pacific Northwest, where it is frequently used on its own and with other grasses.

The fast growth rate of perennial ryegrass makes it well suited for filling out thinning cold season lawns.

Check out my ultimate guide to cool-season grass.

How can you tell perennial ryegrass?

Photo by Forest Starr & Kim Starr

Although it is closely related to the tall fescue in terms of appearance, it has a marked similarity with Kentucky bluegrass. But, that’s till you pluck out a blade. Here are a few noticeable differences:

• This fine-textured grass grows low and has a bunched appearance when used on its own.

• The underside of the blade is conspicuously smooth and shiny and also hairless.

• The blades shine and stand out from other grass varieties in sunlight.

• The color can go from a pale green to a rich deeper green in the flowering season.

• The upper side of the blade is ribbed.

• The seeds have a distinct reddish tinge to them, which earned it the name ryegrass.

• They are awn-less and look papery and almost flat.

• The stem base of the grass seems to take after the seed in terms of color and is a purplish-red.

When to plant perennial ryegrass?

The best time to plant cold season grasses, including perennial ryegrass, is late summer/early autumn or late winter/early spring, depending on where you are and the lawn application of the grass.

Autumn seeding: The idea is to plant when the seeds can get the optimal weather conditions to germinate. This happens when the daytime air temperature reaches 60 to 75 degrees and the soil temperature drops to 50 to 65 degrees F.

Early autumn is the least risky time for planting cold season grasses because the days are still warm enough to facilitate germination but the nights start to get cooler. The lower nighttime temperatures protect the seedling from diseases. Moreover, humidity is also at the right level to encourage faster germination.

If you wait till late fall, things can get risky because the first frost is too close for comfort. A few days of consistent frost can kill seedlings. So, it is best to space things out such that the grass is at the mature stage when the first frost hits the area.

Spring seeding: This is the second-best time of the year to plant perennial ryegrass. Although experts strongly suggest that you go with fall planting, spring seeding may be needed to fill out a thinning lawn or bald spots.

The best time for spring planting is when the temperatures reach 60 degrees F and begin to climb from there. This corresponds to roughly about 2-4 weeks after the last frost. Once again, if the temperatures rise too quickly, the seedlings will get damaged and may even be destroyed.

Check out my ultimate guide to spring lawn care.

For overseeding: When overseeding a cold season lawn with perennial ryegrass, a good starting point would be the end of September or early October for the Upstate areas and late October for the coastal areas and Midlands.

If you intend to overseed a warm-season lawn, wait till the Bermuda grass or any other warm-season grass begins to go dormant before scattering perennial ryegrass seeds. Starting too soon will expose the seeds and seedlings to warmer than needed temperatures.

Also, it will create a competition between the two varieties for nutrients and oxygen. Needless to say, perennial grass seedlings will lose the fight. So, wait till the Bermuda grass begins to go from green to tan. Once the tips of the blades appear limp and tan, you can be sure that the grass has stopped growing and will pose no threat to the seedlings.

How does perennial ryegrass spread?

The tufted appearance of the cool-season grass is attributed to the lack of rhizomes or underground stem system that assists other grasses in their spread. Perennial ryegrass has tillers or vertical shoots that limit its ability to spread. In other words, don’t expect thinned out or bald areas to fill out on their own, as they do with other grasses.

The only way to ensure an even spread of perennial ryegrass is through seeding and overseeding. That said, I have heard about lateral spread varieties of perennial ryegrass. However, I haven’t worked with these, so I won’t comment on them.

Also, there are some old research papers which state that in response to intense grazing and trampling into the ground, some cultivars of perennial ryegrass do develop underground rhizomes and begin to spread horizontally. However, to my knowledge, nobody has witnessed this development in lawns anywhere in the US.

What is the best perennial ryegrass?

At this time, there are more than 200 varieties of perennial ryegrass sold across the United States and dozens are added to this list each year. Most seed sellers have come up with their own names, so it is hard to keep track of them all.

The grass that mingles freely: The thing about perennial ryegrass is that it cross-pollinates with both Italian and annual ryegrass, and that is how these cultivars are formed. In fact, they now also have an intermediate ryegrass that shares the characteristics of both annual and perennial ryegrass.

Deliberate mixing: Moreover, perennial ryegrass seed mixes are often contaminated with annual and Italian/domestic ryegrass.

So, there is no one best perennial ryegrass variety. You can either use a high-quality seed mix that contains 2-3 cultivars exclusively of perennial and not any other type of ryegrass or talk to a seed expert for what would be best suited for your lawn goals.

Is there a difference in the perennial ryegrass used for lawns and for pastures?

ryegrass heat
Photo by Forest Starr & Kim Starr

There is a marked genetic difference between perennial ryegrass used for lawn and pasture applications. The ryegrass used for lawn application has two chromosomes (diploid). It grows low but dense.

The kind used for foraging application has four chromosomes (triploid) and it grows taller than the diploid but isn’t as dense. However, it does offer greater hay yield. Another thing to remember is that diploid (lawn application) perennial ryegrass is often intentionally exposed to a fungal infection (endophytic fungus).

This increases its resistance to many diseases. However, the fungus also leads to the production of chemicals that can be toxic for foraging animals. So, this variety should never be used in pasture applications.

Check out my ultimate guides for different varieties of grass.

Is perennial ryegrass drought resistant?

The cool-season grass has a shallow, fibrous root system that prevents access to the water stored in the deeper soil layers. In fact, perennial ryegrass has a better tolerance for damp soil than other cool-season grass or other varieties of ryegrass.

Also, perennial ryegrass will be the first to show signs of damage due to drought. Put these facts together and it is evident that this cool-season grass loves its H2O. Prolonged drought conditions coupled with the hot summer weather and intense exposure to sunlight can kill perennial ryegrass.

However, the good news is that this grass will quickly show visible signs of it being thirsty. So, homeowners do get a chance to salvage the situation before it gets out of hands.

Does perennial ryegrass go dormant?

Check out my full article on watering your lawn with a sprinkler system.

The cool-season grass does not take too well to soaring summer temperatures. In the same vein, it is also not a big fan of significant plunges in mercury levels. Generally, daytime temperatures that are at or above 87 degrees F spell trouble for this grass.

Even when it isn’t quite so hot during the day, if the night time temperature reaches 77 degrees F or above, perennial ryegrass will become dormant. On the lower side, the growth slows down and even stops if temperatures fall below 41 degrees F. In fact, once this lower range is breached and if the temperatures continue to drop, the grass will die-back.

Does perennial ryegrass die in the summer?

As long as the temperature does not rise above 100 degrees F, there is no risk of perennial ryegrass dying.

However, it will enter the phase of dormancy at the height of summer. The problem with perennial ryegrass is that it isn’t very tolerant of shade, so it has to be grown in areas where it receives ample sunlight.

While this works very well in fall, winter and even early spring, as the sun starts beating down and the temperatures rise, the fine blades and fibrous root system of perennial ryegrass get no reprieve from the intense heat. This leads to overheating, which causes the grass to die back and go dormant.

What temperature does ryegrass die in winter?

Ryegrass varieties are simply not as cold hardy as other cool-season grasses. In fact, the perennial variety cannot handle temperatures in the vicinity of 30 degrees F.

Temperatures in the 30-degree range: If this is common all through winter or even for weeks, there is little you can do to save the green cover of your lawn. All you can do in this case is water the lawn generously in fall and well before a freeze.

The idea is to ensure that the roots are well irrigated before the hard freeze. This way you protect them from the freezing and dry winter weather and the cold air pockets in the soil. If the roots are alive, once the temperatures rise, the grass will grow back with gusto.

The mercury does not dip past 40 degrees: If there is only an intermittent day or two of upper 30 degrees to deal with, there is a trick to protect the grass. However, be warned that this only works if the grass is planted in nutrient-rich and well-drained soil. You can marginally control the temperature with the right watering technique.

Water the lawn late in the morning, which will allow several hours for the evaporation of the moisture. As water evaporates, there is a slight rise in the temperature at the grass blade level. This may get to just a bit over 40 degrees, which would be enough to make the grass survive, but only for a day or two.

Check out my article on how to revive grass after winter.

Will perennial ryegrass come back every year?

If well cared for, a permanent lawn with perennial ryegrass application can last for 3-5 years.

Of course, seeding of the bald spots and overseeding will be required each year. However, you can expect perennial rye to come out of hibernation once the conditions are favorable, which is around early-mid autumn.

Overseeding with perennial ryegrass – How to do it?

  1. Pick a seed mix with at least 3 varieties of perennial ryegrass in it and a high percentage of pure live seed (the seeds that are most likely to germinate).
  2. Measure your lawn by multiplying the length with the breadth. Use the product/area thus calculated to find out the amount of seeds needed. This information is given on the packaging of the seed mix.
  3. Typically, you would use 5 lbs. over an area of 1000 sq.ft for overseeding and twice of that to stop soil erosion and for seeding.
  4. A heavily thatched lawn will lead to irregular patches, so dethatch with vertical cutting.
  5. If core aeration is needed, do this one month prior to overseeding.
  6. Wait till the daytime temperatures are at 70 degrees F and the night time temperatures are above 50 degrees F to overseed. Typically mid-September to mid-October is a good time for overseeding.
  7. 2-3 days before broadcasting the seeds, cut the warm season grass, which should be dormant at this point, to 1/3rd of its length.
  8. Instead of trying to take out the length in one pass, make several passes to remove 1/4th inch at a time, lowering the blades each time. This lowers the stress on the dormant grass.
  9. Remove the grass clippings with a leaf rake or if your mower takes the leaf bag, do things the easy way.
  10. Next, go over the lawn with the garden rake to aerate the soil and loosen the upper layer for better contact of the seeds with the soil.
  11. Pour one-half of the required seeds into the rotary spreader and run through the lawn in vertical columns. Use the remaining half to broadcast the seeds in horizontal rows (perpendicular to the direction of the vertical passes).
  12. If it is an established lawn, go over the turf with a stiff broom to drop the seeds stuck to the foliage on the ground.
  13. Cover the seeds with a layer of mulch/manure or dried, loose mud. Use the rotary spreader once again to apply a uniform cover of 1/8th or 1/4th inch. This will keep the seeds from turning into an easy meal for the birds in the area and will help to retain the moisture needed for germination.
  14. Water the lawn about an inch deep immediately after seed application. Insert a pencil into the wet soil to ensure that the wet soil mark is indeed at inch.
  15. Thereafter, keep the soil moist with light watering 3-4 times a day (10-minute bursts). Be careful not to flood the area as this will bring the seeds to the surface of the water and may even wash them away.
  16. Water as soon as the top dressing of mulch/manure appears to be drying out.
  17. Once you see a green cast on the area, cut back on the watering to once a day.
  18. Keep an eye out for the wilting of the new seedlings. At the first sign of this, increase your frequency of irrigation again.
  19. Go to an alternate day watering schedule when the blades reach a height of 3/4th to 1 inch.
  20. Wait for the grass to grow to 2-3 inches before mowing it for the first time.
  21. Remove the clippings after the first mowing
  22. Thereafter keep the blades at 1.5 to 2.5 inches for optimal protection and growth and water once a week.

Is perennial ryegrass an invasive species?

From what I know, in the US, it isn’t considered an invasive species. But it is regarded as such in New Zealand, where it is found to compete with and kill local flora.

That said, perennial ryegrass is allelopathic. What this means is that the roots of the grass secrete chemicals that are toxic to the plants around them. Don’t worry your trees and shrubs are too big to be at risk. However, this property can impact other grasses used in the seed mix.

Allelopathy can easily be regulated and controlled by limiting the quantity of ryegrass to just 30% of the seed mix. Of course, you won’t have to worry about this if you are using a mix that exclusively contains varieties of perennial ryegrass.

The allelopathic effects of perennial ryegrass can be used to choke out some weeds, particularly crabgrass.

Is perennial ryegrass better than annual ryegrass?

A bag of annual ryegrass seeds (single variety 50 lbs) will set you back by a mere $20 while a perennial ryegrass seed mix will cost you at least thrice as much. Needless to say, there is a reason for the significant price difference.

As its name suggests, annual ryegrass will only serve you for one year. If you plant it in autumn, it will live through winter and early spring and then die. No, the annual variety does not go to sleep in summer-like perennial ryegrass. It dies!

So, with annual ryegrass, you have to start from scratch each fall. In contrast, you will only need some amount of overseeding when working with the perennial variety. Moreover, perennial ryegrass offers a denser turf and is more resilient to wear than the annual variety. Also, the latter does not take too kindly to regular mowing.

Perennial ryegrass vs. Kentucky bluegrass

You should not be pitching perennial ryegrass against Kentucky bluegrass. Instead, you should consider how these two varieties can make up for the drawbacks of each other. That said, if you must draw a comparison, this is what things would look like.

• In terms of color, Kentucky bluegrass simply has no competition with its dark green, almost bluish, hue. In contrast, perennial ryegrass has a light green shade.

• However, what perennial ryegrass lacks in terms of color it makes up for with its rapid speed of establishment. Consider this – With Kentucky bluegrass, you would have to wait for 2-3 weeks for germination and green shade. With perennial ryegrass, you’d be getting ready for your first mowing in that much time.

• Kentucky bluegrass has lower wear tolerance than perennial ryegrass but it restores faster after damage.

• Perennial ryegrass scores high when it comes to diseases and drought tolerance.

• Both varieties are not too tolerant of shade.

• Comparatively, Kentucky bluegrass has lower maintenance requirements.

Is perennial ryegrass good for horses?

No, it isn’t. There was a time when these grasses were considered good but that was before forage research reached its current level of sophistication.

Of course, farmers are still peddling hay from ryegrass because both varieties grow vigorously and the annual variety, in particular, is inexpensive, hence offers greater profit margins. But what about equine nutrition needs?

The problem with ryegrass is that it is sugar dense, low in protein and high in potassium. In other words, it works well on livestock as it makes them gain weight rapidly and increases milk production.

But, and that is big BUT, the seeds of ryegrass (both perennial and annual) are infected with endophytic fungi. I discussed the toxic effects of this infection earlier in the article.

These fungi live inside the plant and produce mycotoxins that act as natural insecticides. And these mycotoxins can do more than just kill pests. They are also toxic to horses and other livestock. These toxins cause the notorious ryegrass staggers in horses. Plus, the mineral content of ryegrass varieties can lead to a mineral imbalance in horses.

The worst part is that ryegrass is like candy to horses, so once they get hold of it, they will keep munching on it for as long as they can. In a nutshell, keep that pony way from ryegrass.

And in conclusion….

So, there you have it folks- that is everything you need to know about decking up your lawn with the vibrant greenery of perennial ryegrass. Because it is a fantastic utility, cool-season grass that thrives on its own and with other grasses, you will find multiple ways in which to use it to meet your lawn goals.

And when it stands tall in all its glory, you will be able to actually enjoy the pristine beauty of your lawn by walking right on the grass without worrying about damaging it. Now, that is what I call good looks with exceptional performance!

Because it establishes easily and grows vociferously, the results are both quick and impressive. Plus, given its popularity, new cultivars with improved characteristics are being introduced just about every year. So, who knows in the future the humble perennial ryegrass may usurp Kentucky bluegrass and become the new king of cool-season lawns?


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