EXERCISE 11

EXERCISE 11: BIOLOGY OF NUT SEDGE

Weed Description:
A perennial grass that has both rhizomes and stolons and is capable of forming a turf or mat of fine leaves. Several varieties of Bermuda grass are cultivated for use as lawn and pasture grasses, however this weed has developed into a very troublesome and hard-to-control weed in agronomic crops, landscapes, nurseries, and turf grass. Bermuda grass is found throughout the southern United States, as far north as southern New Jersey.
Seedling:
Leaves are rolled in the bud, leaf blades are smooth on both surfaces, and the ligules are a row of hairs approximately 1/2 mm long.

Leaves: Leaves are rolled in the bud, without auricles, and have a ligule that is a fringe of hairs approximately 1/2 mm long. Hairs occur at least on the leaf margins in the collar region (the region where the leaf blades oin to the sheath). Leaf blades are approximately 2 to 7 inches long by 2 to 5 mm wide and smooth to only sparsely hairy above but usually only with a few hairs near the leaf base. Leaves emerge from opposite sides of the stem and have margins that are slightly rough.

Stems: Leaf sheaths are usually distinctly flattened with relatively long hairs (1 to 3 mm) near the collar only.

Roots: Rhizomes and stolons both occur on the same plant. Rhizomes are scaly and often form an almost impenetrable mat. Stolons are flat, smooth, usually bent and root at the nodes

Flowers: Inflorescence consists of 3 to 7 fingerlike spikes that originate from a single point. Individual spikes are approximately 1 to 3 inches long and flattened. Spikelets are arranged in 2 rows on each spike and each of these spikelets produces a single lance-shaped seed (1 -1/2 mm long)

Identifying Characteristics:
  • A persistent grass weed with both scaly rhizomes and stolons that root at the nodes.
  • Additionally, the tuft of hairs in the collar region helps to distinguish this weed from most other grasses.
  • Nimblewill (Muhlenbergia schreberi) is similar in appearance and growth habit, however nimblewill plants are generally smaller than those of Bermuda grass and have a membranous ligule unlike the ligule that is a fringe of hairs on bermudagrass.

Purple Nut sedge: Cyperus rotundus:

11.1
Inflorescence of purple nut sedge
 		11.2
Tubers and rhizomes of purple nut sedge
11.3
Tubers and rhizomes of purple nut sedge
 		11.4
Purple nuts edge, Cyperus rotundus


Weed Description: A perennial from rhizomes and tubers that may reach 2 1/2 feet in height. The stems are 3-sided and triangular in cross section and the leaves are yellow to green in color with a distinct ridge. Found throughout the southeastern United States as a common weed of agronomic and horticultural crops, nurseries, turfgrass, and landscapes.
Seedling: Seedlings rarely occur. Most plants from rhizomes and/or tubers. Leaves do not have ligules or auricles and have a distinct ridge along the midvein, but are nevertheless often mistaken for grasses.

Stems: Erect, un branched, and 3-sided and triangular in cross section. Stems are usually solitary and produce terminal spikelets.

Leaves: Dark green in color and have a distinctly shiny appearance. Leaves are 5 to 8 mm wide and have a distinct ridge along the midvein. Leaves are produced in groups of 3 from the base of the plant. Leaves are without hairs (glaucus) and no auricles or ligules are present. The leaves of purple nutsedge taper abruptly to a sharp point, unlike the gradual taper of yellow nutsedge leaves.

Roots: Rhizomes and tubers occur on the same plants. Tubers are oblong, ridged, initially white in color, eventually turning brown or black, and are bitter to the taste. Purple nutsedge produces chains of tubers that develop along the entire rhizome.

Flowers: Spikelets occur at the ends of the solitary stems in a cluster where the flower stalks arise from a common point (umbel-like). Individual spikelets are reddish-purple to reddish-brown in color.

Identifying Characteristics:
• Yellow Nut sedge (Cyperus esculentus) is very similar in appearance and growth habit to purple nut sedge, and the two are often confused.
• The leaves of yellow nutsedge taper to a point gradually whereas those of purple nutsedge taper to a point abruptly.
• Additionally, the seed head of yellow nut sedge is yellow in color, while that of purple nusedge is purple. Lastly, the tubers of purple nut sedge are often connected in chains and bitter to the taste, while those of yellow nut sedge are solitary and sweet to the taste.
• Rice flatsedge (Cyperus iria) and Green Kyllinga (Kyllinga brevifolia) are also similar when young, however rice flatsedge has a fibrous root system and green kyllinga has rhizomes that are usually red to purple in color.


Yellow Nut sedge: Cyperus esculentus:

11.5
Young plant
 		11.6
Flower head
11.7
Yellow nut sedge, Cyperus esculentus, tubers
 		11.8
Yellow nut sedge, Cyperus esculentus, seeds.
11.9
Flowering yellow nut sedge plant


Weed Description: A perennial from rhizomes and tubers that may reach 2 1/2 feet in height. The stems are 3-sided and triangular in cross section and the leaves are yellow to green in color with a distinct ridge. Found throughout North America as a common weed in agronomic and horticultural crops, nurseries, turf grass, and landscapes.

Seedling: Seedlings rarely occur. Most plants arise from rhizomes and/or tubers. Leaves do not have ligules or auricles and have a distinct ridge along the midvein, but are nevertheless often mistaken for grasses.

Leaves: Yellow to green in color and have a distinctly shiny appearance. Leaves are 5 to 8 mm wide and have a distinct ridge along the midvein. Leaves are produced in groups of 3 from the base of the plant. Leaves are without hairs (glabrous) and no auricles or ligules are present. The leaves of yellow nutsedge taper gradually to a sharp point.

Stems: Erect, un branched, and 3-sided and triangular in cross section. Stems are usually solitary and produce terminal spikelets.

Roots: Rhizomes and tubers occur on the same plants. Tubers are round, ridged, initially white in color, eventually turning brown or black, and are sweet to the taste. Yellow nutsedge produces solitary tubers that arise either from the basal bulb or from a rhizome. Several tubers do not arise along the entire rhizome, as in purple nutsedge.

Flowers: Spikelets occur at the ends of the solitary stems in a cluster where the flower stalks arise from a common point (umbel-like). Individual spikelets are yellow to brown in color.

Identifying Characteristics: Purple Nutsedge (Cyperus rotundus) is very similar in appearance and growth habit to yellow nut sedge, and the two are often confused.
  • However, the leaves of purple nut sedge taper to a point abruptly whereas those of yellow nut sedge gradually taper to a point. Additionally, the seed head of purple nut sedge is purple in color, while that of yellow nut sedge is yellow.
  • The tubers of purple nutsedge are often connected in chains and bitter to the taste, while those of yellow nutsedge are solitary and sweet to the taste. Rice flatsedge (Cyperus iria) and Green Kyllinga (Kyllinga brevifolia) are also similar when young, however rice flatsedge has a fibrous root system and green kyllinga has rhizomes that are usually red to purple in color.
Web Links:
1. http://wric.ucdavis.edu/
Last modified: Friday, 9 March 2012, 6:26 AM