Annual Vs. Perennial Ryegrass – Differences

Cold season grasses like Tall fescues, Kentucky bluegrass, and ryegrass dominate the Northern United States regions that experience cold and snowy winters and hot summers. When choosing turf for your lawn,  you want to go for one that best fits your zone and has the best tolerance to lawn problems such as heavy traffic.

Perennial and annual ryegrass can be an excellent choice for your Northern state lawn. Despite their similar characteristics like bunch-type growth and non-spreading, major differences such as life spans, color hues, and their behaviors in different weather conditions can influence your decision. 

We’ll look at these differences so you can make a better decision when choosing between the two varieties for your lawn.

What is annual ryegrass?

Annual ryegrass, scientifically called Lolium multiflorum L is a non-spread, bunch-type growing cool-season grass native to Southern Europe.

Annual ryegrass has a short one-year life cycle. It is widely used in golf courses, athletic fields, and home lawns. Annual rye also chokes weeds and controls soil erosion.

This grass establishes fast; seeds take 3 to 5 days to germinate. It is primarily used to overseed warm-season grasses like Bermuda and Bahiagrass for winter colorizing. You should overseed Annual ryegrass with other grass types in fall. You can grow it solely as a seed or mix it with small grains or clover.

This grass has coarse-textured, light green leaf blades joined to an overlapping, hairless sheath at the collar. The leaves are 4 to 10mm broad, sharply taper pointed and keeled, but rolled in the buds. The lower surface of the blades is smooth and glossy, hairless, and prominent in the buds. Furthermore, the leaf margin feels rough when touched.

The inflorescence consists of 3 to 6 inches tall spikes, with many spikelets that contain multiple florets. These spikelets are arranged directly to the central axis. The stems of this grass are about 12 to 40 inches tall, depending on the variety and soil conditions. They have nodes or internodes, each having a leaf.

This grass has densely branched fibrous and sometimes adventitious roots. However, stolons and rhizomes are absent.

Annual ryegrass is hardy in zones 4 to 9, from the Gold Coast North to the transition zone. It needs an optimum temperature of 68oF to 77oF in fall and spring when actively growing. Temperatures higher than 81oF stress it.

This grass prefers well-drained fertile soils with enough moisture. It can, however, tolerate poorly drained soils with long periods of continuous flooding if the temperature is below 71oF.

The soil should be moderately acidic, with a short-term 6.0 to 7.0. You need a soil test to determine whether it meets the required pH level. Lime or sulfur corrects any pH imbalances if there are any. Annual ryegrass requires a maximum of 3 lbs of Nitrogen fertilizer per 1000 square feet yearly, with 0.5 to 1.0 lbs per 1000 square feet of lawn in a single application after soil analysis.

While this grass needs full sun, it can tolerate partial shade. It moderately stands heavy foot traffic but is more susceptible to diseases like brown light. In hot, dry summers, it becomes dormant.

Mow overseeded annual ryegrass after 3 to 7 days, depending on the height of the other grass. 

What is perennial rye?

Perennial rye, also known as Lolium perenne L, is a bunch type growing, cool-season grass native to Europe, Asia, and North Africa. It produces tillers, therefore, doesn’t spread.

Perennial rye is a favorite on golf courses, athletic fields, and home lawns.  While it’s a short-term grass, its dazzling green and soil erosion benefits appeal to commercial and residential areas. 

Perennial rye grows fast and is primarily used for overseeding warm-season grasses like Bermuda grass to provide winter color. Its rapid emergence suppresses and controls weeds. It can also blend with other cool-season grasses like Tall fescues, Kentucky bluegrass, and Annual ryegrass for more traffic tolerance and disease resistance. It is usually seeded alone or mixed with clover.

The leaf blades of this grass have a fine texture and are dark green. New young leaves emerge folded from the leaf sheath. The lower surface of the leaves is smooth and glossy but with ridges on the upper area. The leaf tips are pointed and boat-shaped. It has an arching keel down the center of the leaf.

Perennial rye has a short (1- 2.5mm long) membranous ligule pointed at the apex. Its auricles are straight and clasp the stem. When flowers mature in early spring, they produce 2 to 10 inches wide spikes with many spikelets that contain multiple florets.

Perennial rye thrives best in hardy zones of 5 to 7 with moderate temperature throughout the year. It is also adapted to grow in all well-drained fertile soils or soils that remain wet for more extended periods of the year. The soil should be less acidic with a pH of 6.0 -7.0.

Perennial ryegrass prefers full sun. However, it can tolerate partial shade. It can also withstand moderate cold.

It withstands heavy foot traffic, hence the best traffic tolerant cold-season grass. Perennial ryegrass stands moderate drought but dies when the conditions worsen. However, watering once to thrice per week in the hot summer keeps it fresh.

Perennial ryegrass requires the highest amounts of nitrogen (4-8lbs of Nitrogen fertilizer per 1000 square feet of lawn yearly) than other grasses. Limited nitrogen supply exposes it to diseases like; red thread, pink patch, and crown rust which thin it.

Perennial rye should be mowed every 3-7 days using a reel or rotary mower. The mowing height depends on the warm season grass it’s overseeded with.

Annual vs. Perennial Ryegrass – Differences

Annual and perennial ryegrass have vast differences in their life cycle, tolerance to lawn problems, and identifying features. Let’s look at these in detail.

Here`s a summary table for the significant differences between annual ryegrass and perennial rye.

Annual ryegrassPerennial rye
One life season3-5 life seasons
Light green leaf bladesDark green leaf blades
Rolled vernationFolded vernation
Coarse textured leavesFine textured leaves
Hardy in zones 4-9Hardy in zones 5-7
Tolerates moderate trafficTolerates heavy traffic
Resistant to diseaseSusceptible to disease
Highly tolerates  coldLess cold tolerant
High shade tolerantLess shade tolerant

1. Life cycle

Annual ryegrass has a life cycle of one season, while perennial rye has 3-5 life seasons.

Annual ryegrass grows and dies after every year. Its seeds are planted in late summer or early fall, and they take between 3 to 7 days to germinate. The grass crowns and produces shoots before winter, then becomes dormant.

At the onset of spring, temperatures steadily rise, growth restarts, and seedheads emerge. This grass becomes dormant and dies when daytime temperatures rise above 90oF in summer. The seedheads produce new seeds germinating in early fall, and the cycle restarts.

On the contrary, perennial rye has a 3-5 years long lifespan. Its grass seeds take between 3 to 7 days to germinate. The grass lies dormant in the cold winter months (late November through early to mid-March). During spring, it actively grows and reaches its peak in May to June.

Perennial ryegrass becomes dormant and turns brown at the onset of summer. It recovers from the hot temperature stress in early fall, and the cycle restarts.

2 . Leaf color

Annual ryegrass has light green leaves, while perennial rye has dark green leaves. The leaf blades of annual ryegrass are lime-green, with their lower surface smooth and glossy.

On the other hand, perennial rye leaf blades are dark greener and retain the color in most parts of the year except in the hot summer months. Perennial rye is a more preferable choice for overseeding warm-season grasses like Bermuda due to its color intensity. 

3. Vernation

Annual rye has a rolled vernation, while perennial rye has a folded vernation.

New young leaf blades (also called shoots) of annual ryegrass emerge rolled at the bud. The bud later expands through the rolled shoots.

Meanwhile, new young leaves emerge folded in perennial rye. It’s from the folded shoots that the bud later expands from.

4. Leaf texture

Annual ryegrass leaves have a coarse texture, unlike perennial’s fine-textured leaves.

The leaf margins of the annual rye feel rough when touched. They are, however, smooth and glossy on the lower surface.

Meanwhile,  perennial rye has fine-tuned texture leaves that feel smooth when touched. Just like annual rye, its lower surface is smooth and glossy.

5. Growing zones

Annual ryegrass grows in zones 4 to 9, while perennial rye grows in zones 5-7.

Annual ryegrass thrives best in zones 4 to 9 which experience colder winters and hotter summers. The average winter temperature in these zones is between -30oF and 30oF. Annual ryegrass is cold-tolerant. Therefore, it becomes dormant and survives the cold season.

Meanwhile, annual rye prefers less cold zones of 5 to 9, where the temperature range is between -20oF and 10oF. The grass is better adapted to cold winters and warmer summer months.

6. Traffic tolerance

Annual rye withstands moderate foot traffic, while perennial rye withstands heavy foot traffic.

Annual rye is a sustains minimal wear and tear in low to moderate traffic lawns. Hence, it would be a great fit for an ornamental walkway. Conversely, perennial rye makes an excellent choice for lawns with heavy foot traffic as it doesn’t break. This grass withstands the most traffic among all cold season grasses, making it the most popular grass for golf courses.

7. Disease resistance

Annual ryegrass is more resistant to turf diseases, while perennial rye is more susceptible to infections.

Common lawn diseases like crown rusts and brown blight are less common in annual ryegrass. On the contrary, these diseases are more prevalent in lawns with perennial rye. This grass is also vulnerable to red thread disease, although it moderately resists it. 

8. Cold tolerance

Annual rye is highly cold-tolerant, while perennial rye is less cold tolerant.

Annual rye is hardy in zones 4 to 9, which experience freezing winters. Therefore, it is adapted to survive in such areas.

Meanwhile, perennial rye performs dismally in colder areas. It’s most suitable for zones 5 to 7, which experience less cold winters.

9. Shade tolerance

Annual rye tolerates more shade, while perennial rye thrives in direct sunlight.

Though annual rye needs full sun to survive, it will still grow in shade. Conversely, perennial rye withstands only moderate shade.

References

  1. Texas A & M University: Annual Ryegrass.
  2. Oregon state University: Perennial ryegrass Lolium perenne L.

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