Perennial ryegrass (Lolium perenne) is a bunch-type grass that is used for winter overseeding on sites where high quality and winter color are needed. The texture, color, and density of perennial ryegrass are very similar to those of Kentucky bluegrass. Perennial ryegrass is often utilized for winter overseeding on golf course fairways and teeboxes, athletic fields, and high profile home lawns. Perennial ryegrass is often confused with tall fescue and / or Kentucky bluegrass. However, Kentucky bluegrass has a boat-shaped leaf tip and distinctive light-colored lines on both sides of the midrib. Tall fescue has rough leaf blade margins whereas perennial ryegrass has smooth ones. Also, tall fescue has rolled vernation in the leaf bud and perennial ryegrass has folded vernation.

Cultural Control

Perennial ryegrass is often overseeded to provide winter color in warm climates where turf is utilized in winter months. When warm weather prevails in late spring or early summer, this species usually will not survive. However, in the transition zone, especially during cool summers, wet summers, or both, perennial ryegrass can survive the summer and often becomes clumpy. This very attractive turf species becomes a difficult-to-control weed in these conditions. Control strategies should concentrate on controlling perennial ryegrass before it becomes clumpy.

• SEEDHEAD / FLOWER
  • a spike, with flattened spikelets along each stem
• VERNATION TYPE
  • leaves folded in the bud
    Figure 1, Figure 2
• LIGULE TYPE
  • membranous; collar-like to blunt, may be toothed near top, 0.02 - 0.06 inches (0.5 - 1.5 mm) long
    Figure 3, Figure 4
• GROWTH SEASON / LIFE CYCLE
  • cool season turf or perennial weed
• AURICLE TYPE
  • rudimentary
    ​Figure 5, Figure 6, Figure 7
• LEAF BLADE TIP SHAPE
  • sharp-pointed; bright green, sharply creased, deeply ridged upper surface, lower surface smooth and glossy, edges slightly rough
    Figure 8
• LEAF BLADE WIDTH
  • 0.08 - 0.2 inches (2 - 5 mm) wide
• STOLON PRESENCE
  • absent
• RHIZOME PRESENCE
  • absent
• COLLAR TYPE
  • divided by midrib, not hairy, distinct
• SHEATH TYPE
  • sheath is usually flattened, reddish at base

Figure 1. Perennial ryegrass vernation.

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Figure 1. Perennial ryegrass vernation.

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Figure 2. Perennial ryegrass vernation.

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Figure 2. Perennial ryegrass vernation.

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Figure 3. Perennial ryegrass ligule.

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Figure 3. Perennial ryegrass ligule.

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Figure 4. Perennial ryegrass ligule.

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Figure 4. Perennial ryegrass ligule.

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Figure 5. Perennial ryegrass auricle.

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Figure 5. Perennial ryegrass auricle.

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Figure 6. Perennial ryegrass auricle.

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Figure 6. Perennial ryegrass auricle.

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Figure 7. Perennial ryegrass auricle.

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Figure 7. Perennial ryegrass auricle.

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Figure 8. Perennial ryegrass leaf blade.

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Figure 8. Perennial ryegrass leaf blade.

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