Articles
Identifying Common Pennsylvania Grasses
Grass identification tips and techniques.
Updated:
January 24, 2013
Structures Used to Identify Grasses
Recommended if ligule or auricle are unfamiliar words.
Awn: a bristle characteristic of the spikelets in some grasses.
Internode: Area of the stem between two nodes.
Node: A joint where a leaf is or was attached to a stem.
Rhizome: A stem that grows horizontally below the ground surface and may form adventitious roots at the nodes.
Stolon: A stem that grows horizontally above the ground surface and may form adventitious roots and a new plant at the nodes.
Detailed Diagrams of Structures
Photos of Grasses
Identification Matrix
Recommended if you are familiar with grass structures.
| Grass Species | Life Cycle Plant Height | Sheath | Blade | Collar | Auricles | Ligule | Stem | Inflor- escence | Comments |
|---|---|---|---|---|---|---|---|---|---|
| Barnyard grass Echinochloa muricata Beauv. | Annual 1-3 ft | Over- lapping | 1-15mm wide. Flat with rough edges. | Broad | None | None | Round and branching at nodes. | Panicle of spike-like branches. | Found in late summer/ early fall. Seed structures purplish and covered with short stiff bristles. |
| Bermudagrass Cynodon dactylon L. | Perennial/ Annual 1-2 ft | Papery | 8-15 mm wide. Hairy on top and bottom. | Narrow | None | Fringe of hairs | Prostrate and upright | 3-7 spiked branches originating from a single whorl. | Spreads by both stolons and rhizomes. Found as a perennial only in very southern PA and further south. |
| Big Bluestem Andropogon gerardii Vitman | Perennial 7-9 ft | Split, hairy | 10-14mm wide. Smooth with fringe of hairs at junction of blade and sheath. | Narrow | None | Short membrane | Round and upright | Raceme, red in color. | Stems purplish at base. Awns in seed clusters makes inflo-rescence look hairy. |
| Crabgrass (Large) Digitaria sanguinalis L. | Annual 2-3 ft | Over- lapping | 5-12 mm wide. Rough edges with hairs on both sides. Red-purple color. | Broad and divided | None | Membrane. Rounded at top | Upright to prostrate | 3-10 spiked branches in whorls at top of stem. | Found in late summer/ early fall. |
| Crabgrass (Smooth) Digitaria ischaemum L. | Annual 1-2 ft | Over- lapping | 5-12mm wide with no hairs on either side. More purplish than Large Crabgrass | Broad and divided | None | Membrane. Rounded at top | Upright to prostrate | 3-10 spiked branches in whorls at top of stem. | Found in lawns or heavily grazed pastures in late summer/ early fall. |
| Fall panicum Panicum dichotomiflorum Michx. | Annual 1-4 ft | Over- lapping | 10-20 mm wide. Smooth or sparsely hairy near base | Broad | None | Fringe of hairs | Upright to prostrate | Fine, wide- spreading panicle | Found in late summer/ early fall. |
| Giant foxtail Setaria faberi. | Annual 3-6 ft | Over- lapping. Edges are hairy | 10-20 mm wide. Hairy on top and smooth on bottom. | Broad and hairy on edges | None | Fringe of hairs | Round and upright | Spike-like panicle, bristly, drooping | Inflo-rescence bushy like a fox's tail. Hairy blade is key to identification. |
| Green foxtail Setaria viridis L. | Annual 1-3 ft | Over- lapping. Edges are hairy | 5-12 mm wide. Not hairy on top or bottom. | Broad and sometimes hairy | None | Fringe of hairs | Round and upright | Spike-like panicle, bristly | Inflo-rescence bushy like a fox's tail and slightly purple in color. No hairs on leaves. |
| Italian ryegrass Lolium italicum Parn. | Annual to Perennial 1-2 ft | Over- lapping | 2-6 mm wide. Flat and pointed at tip. Waxy. | May be divided | Overlapping | Membrane. Rounded at top | Round-to-flat | Slender stiff spike with awns. | Bunchgrass with waxy leaves that are shiny. Spikelet edge against stem. |
| Kentucky bluegrass Poa pratenis L. | Perennial 1-2 ft | Split | 2-5 mm wide. Boat-shaped tip. | Broad | None | Very short membrane. | Round-to-flat | Fine pannicle | Sod-grass (short rhizomes) dark green. Invades overgrazed pastures. |
| Nimblewill Muhlenbergia schreberi Gmel. | Perennial 1-2 ft | Split and over- lapping | 2-4 mm wide. Rough on top with hairs behind ligule. | Narrow | None | Short membrane | Mostly prostrate | Many fine, slender panicles. | Sod-forming (stolons). Flowers in late summer to early fall. |
| Orchardgrass Dactylis glomerata L. | Perennial 1-3 ft | Split | 5-12 mm wide. V-shaped at base, flat and pointed at tip. | Broad and divided | None | White membrane, pointed at top | Flat | Course panicle. | Bunchgrass. Light green in color. |
| Perennial ryegrass Lolium perenne L. | Perennial 1-2 ft | Over- lapping | 2-6 mm wide. Folded in shoot V-shapped, Waxy | Narrow, may be divided | Short | Membrane, toothed at top | Round-to-flat | Slender stiff spike. No awns. | Short growing bunchgrass with waxy leaves that are shiny. Spikelet placed with edge against stem. |
| Quackgrass Elytrigia repens. | Perennial 1-3 ft | Over- lapping with hairs | 5-10 mm wide. Slightly hairy on upper surface. | Broad and divided | Long- clasping | Short membrane | Round | Slender stiff spike | Sod forming with prominent fast spreading rhizomes. Spikelet flat against stem. |
| Red top Agrostis gigantea Roth | Perennial 1-3 ft | Over- lapping | 2-7 mm wide. Flat. | Broad and V-shaped. | None | Tall membrane | Round | Panicle. Rust colored at maturity. | Sod-grass (short rhizomes). Prominent ridges on upper surface of blade. |
| Reed canarygrass Phalaris arundinacea L. | Perennial 1-6 ft | Over- lapping | 10-20 mm wide. Flat with rough edges. | Narrow and continuous. Yellow. | None | Prominent membrane | Round | Panicle | Sod forming (prominent rhizomes.) |
| Smooth bromegrass Bromus inermis L. | Perennial 1-3 ft | Closed | 4-12 mm wide. Flat and pointed at tip. | Narrow and divided | None | Short membrane | Round | Large panicle, often drooping | Young plants may have pubescence on sheath. Rhizomes covered with brown papery scales. |
| Switchgrass Panicum virgatum L. | Perennial 3-8 ft | Split, with hairy margin | 7-14 mm wide. Hairy on top. | Broad, often with hairs. | None | Fringe of short hairs | Round and upright | Large panicle | Leaves covered with hairs. Spreads by rhizomes. |
| Tall Fescue Festuca arundinacea Schreb. | Perennial 1-3 ft | Over- lapping | 5-10 mm wide. Dark green. Very rough edges | Broad and divided. Wrinkled on edges | Blunt with few hairs | Short membrane | Round | Spreading panicle | Bunchgrass. Prominently veined, leathery, dark green leaves with rough edges. |
| Timothy Phleum pretense L. | Perennial 2-3 ft | Over- lapping | 4-12 mm wide. Flat and pointed at tip | Broad and continuous | None | White membrane with two notches | Round | Spike-like panicle | Bunchgrass with corms (onion-like bulb at base of stem) |
| Witchgrass Panicum capillare L. | Annual 1-3 ft | Over- lapping | 8-15 mm wide. Hairy on top and bottom | Narrow | None | Fringe of hairs | Round and upright | Large panicle | Leaves covered with hairs. Large panicle often breaking off of stem. |
| Yellow foxtail Setaria glauca. | Annual 1-3 ft | Over- lapping, not hairy | 5-10 mm wide. Hairy only on top near base of blade. | Broad and hairy on edges | None | Fringe of hairs | Round and upright | Spike-like panicle, bristly | Inflo- rescence is bushy like a fox's tail. Hairs only on upper surface of blade near base. |
Glossary
Annual: A plant that completes its life cycle and dies within a year.
Awn: A bristle characteristic of the spikelets in some grasses.
Bunchgrass: Plant has no stolons or rhizomes and consequently grows in a bunch rather than spreading.
Inflorescence: Flower structure of a grass plant.
Node: A joint where a leaf is or was attached to a stem.
Panicle: A type of flower in which the flower clusters are attached to the stem via branches connected to branches off the stem.
Perennial: A plant that lives through three or more seasons.
Prostrate: Growing flat along the ground.
Raceme: A type of flower in which the flower clusters are attached to the stem via branches.
Rhizome: A stem that grows horizontally along the ground surface and may form adventitious roots at the nodes.
Sheath: Base portion of the grass leaf that wraps around the stem.
Spike: A type of flower in which the flower clusters are attached directly to the stem.
Stolon: A stem that grows horizontally along the ground surface and may form adventitious roots and a new plant at the nodes.
