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Purple nutsedge

Purple nutsedge

Purple nutsedge

(Cyperus rotundus)

Priority: -  Prevent

Tags: Agricultural | Terrestrial

Identification and Reproduction

Identification:

  • Purple nutsedge is a perennial sedge that can reach up to 1 m tall. 
  • Stems are smooth, triangular and long. 

  • Leaves are attached at the basal portion of the stem. They have a distinct mid-rib and taper to a point. 

  • Flowers are found in a umbel-like cluster and are purple to brown in colour. There are also short leaf-like bracts under the flower clusters. 

Reproduction: 

  • Reproduces from tubers that store food that will help it complete its life cycle the following year. 
  • Tubers can also remain dormant in the soil and then when conditions are favourable they will establish new plants. 
  • Any tubers that are left in the ground will resprout. 

Habitat & Ecology

  • It is well adapted to moist and sandy conditions, but prefers drier conditions. 
  • Shade intolerant. 
  • Purple nutsedge has been observed a various sites including cultivated fields, roadsides, pastures, riverbanks, sandbanks, irrigation channels and wastelands. 
  • Currently it has yet to be found in BC, but purple nutsedge nutlets have been found in imported ornamental nursery stock. 

Impacts

Social: 

  • They invade turf, landscape areas, pastures and cultivated fields. 
  • Reduces crop yields. 
  • Extremely competitive and will take up space and nutrients rapidly. Crop species will be negatively impacted. 

Ecological: 

  • Displace native vegetation. 
  • Will deplete nutrients from the soil and store them in its tubers. 

Management

Prevention is a high priority for this plant. 

  • Use clean seed, hay, grain and straw.
  • Maintain a healthy pasture and good crop cover to reduce ground exposure. 
  • Contact the Canadian Food Inspection Agency (CFIA) if you think you have seen this plant. 

Mechanical/Manual Control:

  • Mechanical removal will need to be repeated in order to deplete tubers of resources. 
  • Do not cut stems as this will trigger tubers to form new rhizomes. 
  • Soil cultivation can be effective only if the tubers are destroyed. Should be repeated every 2-3 weeks to distrupt plant growth. 

Chemical Control: 

  • Many herbicides will kill the foliage of the plant but it is most important to kill the tubers. Currently glyphosate can be used on purple nutsedge. Applications should be applied 3-4 times in a growing season to effectively control it. 
  • Please carefully read product labels prior to application. 

Resources

Download A Guide to Weeds in British Columbia for Purple Nutsedge here

For more details check out the Invasive Species Compendium datasheet on Cyperus rotundus (purple nutsedge). 

Header photo (Jeevan Jose