kili'o'opu Cyperus rotundus

Cyperus rotundus, or Purple Nutsedge, is a perennial, glossy-green, grass-like Eurasian sedge or weed with an erect triangular stem branching into three stems of purple, antenna-like seedpods. Plants die back to the ground in fall, with new shoots emerging in spring from underground tubers. This species, as well as other sedges, grows best in wet sites, prefers warm weather and full sun conditions, but will grow in a diversity of sites and environments.

Like its native cousin, Yellow Nutsedge (Cyperus esculentus), Purple Nutsedge spreads through slender elongated rhizomes and tubers found at the base of the stem and is destructive to crops in sunny, open fields and dry, disturbed soil. The rhizomes remove nutrients from the soil robbing their fellow plants and can be very difficult to remove. If you pull it up you can see the nut-like nodules that store the nutrients (and are edible) as well as a network of long roots. Unfortunately, once pulled up, the Nutsedge may leave broken roots to form more numerous roots and therefore, new plants in its place and seeds lay dormant for several years. It is best to remove young plants and leave exposed roots in the sun to dry out. It is considered one of the world’s worst weeds and is reported in more than 90 countries as a weed infesting at least 52 different crops.

Diseases, Insects, and Other Plant Problems:

No known insect or disease problems. This plant is allelopathic and removes nutrients from soil and its existence in a field significantly reduces crop yield. It is resistant to most herbicides and is one of the few weeds that cannot be stopped with plastic mulch.