Identification of Grass Weeds in Florida Citrus1
Grass weeds commonly found in citrus can be identified by looking for specific characteristics of the plant. These specific characteristics can include, but are not limited to, the width of the leaf blade, presence or absence of hairs, growth habit, type of seed head, root system, and plant size. The entire leaf can be further divided into the sheath, ligule, and blade to also aid in identification. The sheath is the lower part of the leaf that fits around the stem. The projection at the base of the leaf blade is called a ligule. The ligule may be either a membrane or a fringe of hairs or a combination of both. Additionally, the presence of other factors such as stolons (above ground stems) or rhizomes (under ground stems) can also be helpful in plant identification.
Grass seedlings have one leaf as they emerge from seed, whereas broadleaf plants have two. Leaves are generally narrow, grow upright, and have parallel veins in the leaf blade. Grasses usually grow and develop with a fibrous root system that lacks a central taproot. The stems are round and can be either hollow or solid.
Grasses are classified as either annuals or perennials. Annual plants will complete their life cycle in one year (12 months) or less. Perennials will live more than two years (24 months).
The following 12 grass plants are weeds commonly found in citrus groves and other disturbed and cultivated sites in the state of Florida. The characteristics discussed in this article should help you with identification. Please see Figure 13 for a line drawing of the parts of the leaf.
Guineagrass Panicum maximum
Season: annual or perennial
Stem:
Geight: to 16 feet
Growth habit: densely tufted, sometimes bending, rooting at nodes
Roots: fibrous
Hairs: none to hairy
Joints: smooth to usually hairy
Leaf:
Sheath: usually hairy or smooth
Ligule: small membrane, fringed with tiny hairs
Blade: light green, flat, up to 1 3/4 inches in width and up to 30 inches long
Seed head: large, to 3 feet long with spreading branches, lowest branches always whorled
Seed: small, with fine wrinkles, 1/8 inch (2.7-3.7 mm) long
Propagation: reproduces by seeds and rarely by stolons
Comments: identified by the lowest seed head branches whorled and seeds with wrinkles
Narrowleaf Guineagrass Panicum maximum
Characteristics are similar to guineagrass except for the following:
Season: perennial
Stem:
Height: to 5 feet, but can lean and climb through other vegetation reaching 20 feet or more
Growth habit: bending, rooting, and branching at nodes
Leaf:
Blade: to 1/2 inch in width
Propagated by: seeds and stolons
Comments: prolifically branching at nodes, can literally fill a citrus tree with branches and grow through and out of the top of the tree; identified by the same characteristics as guineagrass, but blade only 1/2 inch or less wide
Torpedograss Panicum repens
Season: perennial
Stem:
Height: 1-3 feet tall
Growth habit: erect or leaning stems, grows horizontally by underground rhizomes which sprout stems from nodes, end of underground rhizome is white and sharply torpedo-shaped
Roots: fibrous with rhizomes
Hairs: none
Joints: smooth
Leaf:
Sheath: with or without hairs, sheath margin fringed with short hairs and with long hairs at top
Ligule: tiny membrane fringed with tiny hairs
Blade: narrow, 2-10 inches long, 1/16 to 1/4 inch wide, folded or flat, long soft hairs on upper surface
Seed head: stiff, branched and open, 3-9 inches long
Seed: 1/8 inch (2.2-3.1 mm) long, white, smooth
Propagated by: primarily by rhizomes, but seeds germinate easily
Comments: requires moisture to germinate, prefers wet areas; identified by white rhizomes, white seeds on stalks, and soft hairs on upper blade surface
Broadleaf Signalgrass Urochloa platyphylla (Brachiaria platyphylla)
Season: summer annual
Stem:
Height: to 3 feet tall
Growth habit: spreading, multi-branched, rooting at lower nodes
Roots: fibrous
Hairs: none
Joints: hairy
Leaf:
Sheath: hairs on margin and sometimes on sheath
Ligule: tiny membrane with very short hairs
Blade: to 6 inches long and to 1/2 inch wide
Seed head: up to 12 inches long with 2-6, 1-3 inch long branches
Seed: 3/16 inch (3.5-4.7 mm) long, smooth
Propagated by: seeds
Comments: identified by fibrous roots, hairy ligule, broad blades, smooth sheath, alternate branches in seed head, smooth seeds
Smallflowered Alexandergrass Urochloa subquadripara (Brachiaria subquadripara)
Season: short-lived perennial
Stem:
Height: to 2 feet tall
Growth habit: erect to bending, rooting at nodes, with weak stolons
Roots: fibrous
Hairs: none
Joints: smooth
Leaf:
Sheath: stiff hairs, sheath margin usually fringed with hairs
Ligule: tiny membrane with a fringe of hairs
Blade: with scattered stiff hairs
Seed head: 2 to 7 alternate branches
Seed: 1/8 inch (3.3-3.8 mm) long, smooth
Propagated by: seeds and stolons
Comments: blade tips turn white after frost or cutting; identified by fibrous roots, rooting stems, hairy ligule, hairy sheath, hairy blade, alternate branches in seed head, smooth seeds, leaf tips often white
Southern Sandbur Cenchrus echinatus
Season: summer annual
Stem:
Height: ½ to 2 feet tall
Growth habit: erect or spreading, in clumps, rooting at lower nodes
Roots: fibrous
Hairs: none
Joints: smooth
Leaf:
Sheath: smooth, margin often hairy
Ligule: hairy ring
Blade: to 12 inches long and to 1/2 inch wide, sometimes hairy on upper surface
Seed head: contains a spike of spiny burs which contain 2 to 3 seeds per bur, 5-22 burs per spikelet
Seed: 1/4 inch (4.8-6.8 mm) long, smooth
Propagated by: seed
Comments: identified by spiny burs with flattened spines over most of the bur and a ring of round spines arranged in a crown around the base
Crowfootgrass Dactyloctenium aegyptium
Season: summer annual
Stem:
Height: to 2 feet tall
Growth habit: upward bending, spreading and branching, forming a mat which may root at nodes
Roots: fibrous
Hairs: none
Joints: smooth
Leaf:
Sheath: lacking hairs
Ligule: membranous with a fringe of hairs
Blade: with or without hairs, blade margin with long ciliate hairs from base to almost tip
Seed head: 1-7 short, finger-like thick spikes joined at the same point at tip of stem, branches with claw-like tips
Seed: 1/8 inch (4.0 mm) long, 3-5 joined together
Propagated by: seeds
Comments: identified by fibrous roots, stiff hairs on blade margins, tip of seed head branches claw-like
Natalgrass Melinis repens (Rhynchelytrum repens)
Season: short lived perennial
Stem:
Height: to 40 inches
Growth habit: erect or ascending, from clumps
Roots: fibrous
Hairs: none
Joints: smooth
Leaf:
Sheath: smooth or hairy
Ligule: tiny membrane, fringed with hairs
Blade: flat, to 7 inches long, to 1/4 inch wide, smooth to sandpapery to hairy
Seed head: white at first but turns a showy red or purple, often fading to white again after maturity
Seed: 3/16 inch (2.5-4.7 mm) long, hairy
Propagated by: seeds
Comments: identified by a clump with fibrous roots, hairy seed heads, with long reddish hairs on seeds
Bermudagrass Cynodon dactylon
Season: creeping perennial
Stem:
Height: 4 to 36 inches tall
Growth habit: spreading
Roots: fibrous, rooting from nodes, stolons, and rhizomes
Hairs: none
Joints: flattened, hairless, bearing dead leaf sheaths at each joint
Leaf:
Sheath: with or without hairs, sheath margin with long hairs at collar
Ligule: membrane with a fringe of hairs
Blade: with or without hairs on both surfaces, 1-7 inches long and 1/10-2/10 inch wide
Seed head: erect, with 3 to 9 finger-like branches 1-4 inches (3-10 cm) long, all at tip
Seed: flattened, 1/8 inch (2.0-3.2 mm) long, hairy
Propagated by: seed, surface-creeping stems (stolons), and rhizomes
Comments: used extensively for forage and turf; identified by rhizomes, stolons, narrow blades, erect hairs resembling cat's whiskers on margins of collar
Johnsongrass Sorghum halepense
Season: perennial
Stem:
Height: 4-10 feet tall
Growth habit: coarse, very leafy, erect, perennial, forming dense stands
Roots: fibrous with thick rhizomes
Hairs: none
Joints: smooth
Leaf:
Sheath: with a few hairs
Ligule: prominent membranous ligule
Blade: with prominent white midvein, hairs at the base of leaf blade, to 20 inches long and 1/4 to 1 inch wide
Seed head: large, open, often reddish to purple in color, 6-24 inches (15-60 cm) long
Seed: hairy, about 1/8-1/4 inch (3.8-6.3 mm) long
Propagation: reproduces by seeds and rhizomes, the rhizomes are scaly and sharp-pointed
Comments: identified by thick white rhizomes, a membranous ligule, large seed head, hairy seeds
Vaseygrass Paspalum urvillei
Season: perennial
Stem:
Height: 2 to 9 feet tall
Growth habit: erect, forming large clumps
Roots: fibrous with very short rhizomes
Hairs: none
Joints: smooth
Leaf:
Sheath: hairy to smooth
Ligule: membranous to 3/4 inch (21.0 mm) long, pointed
Blade: with tuft or fringe of long hairs at base just above ligule otherwise without other hairs
Seed head: erect, 4 to 30 spreading branches, spikelet paired
Seed: 3/16 inch (2.0-2.7 mm) long, hairy, flat on one side
Propagated by: seeds
Comments: identified by growing in clumps, membranous ligules, hairy seeds, a band of hairs at base of blade next to ligule, stiff hairs on sheaths at bottom of stem, sheaths smooth at top of stem
Goosegrass Eleusine indica
Season: summer annual, or short lived perennial
Stem:
Height: to 2 feet tall, stems somewhat flattened at base, forming a basal clump with radiating stems, usually nearly prostrate (low growing)
Growth habit: erect to spreading with branched stems which occasionally root from nodes
Roots: fibrous
Hairs: none
Joints: smooth
Leaf:
Sheath - with hairs on margin and long hairs at margin of collar
Ligule - membranous with a fringe of hairs
Blade - to 15 inches long and 3/8 inch wide; upper surface smooth, or with scattered hairs
Seed head: 2 to 7 finger-like branches located at stem end, 1-6 inches long, all clustered at stem tip, usually with one branch on stem below tip
Seed: 1/8 inch (2.7-4.2 mm) long, smooth
Propagated by: seeds
Comments: especially common in compacted soils; prolific seed producer; identified by fibrous roots, usually flattened stems, clear/white sheath margins, seed head with 1 branch below tip
Vegetative Grass Parts
Credit: David W. Hall. 1982. Weeds in the Sunshine: Information for Control of Florida weeds—Common Weedy Grass Identification Using Vegetative Characteristics. Gainesville: University of Florida Institute of Food and Agricultural Sciences.
