Latin name: Cyperus esculentus

Family: Cyperaceae

Common name: Yellow nutsedge

Life cycle: perennial
Habit: Upright with grass-like foliage (but nutsedge is not a grass!!!!!).
Foliage:  Long, glossy, 3-ranked, linear leaves.  At a glance, leaves appear similar to grass.  Nutsedge leaves are angular, with a cross-sectional view appearing like the letter 'W'.  

Cotyledon or seedling:  Nutsedge plants most often emerge from tubers.  Foliage emerging from tubers appears similar to mature foliage, just smaller.
Roots:  Fibrous root system.  Nutlets (tubers, really) develop within the root system, from which new plants develop.  New plants emerging from nutlets are difficult to control with preemergence herbicides, and generally only products containing the active ingredient metolachlor (such as Pennant) will provide acceptable preemergence control.   Plants also spread by rhizomes.
Emergence: Yellow nutsedge emerges when soil temperatures are sufficiently high, usually in mid-April.

Special considerations:  In Oregon, only yellow nutsedge is problematic.  Some growers have reported seeing purple nutsedge, but also stated that it did not persist year after year.  This may be due to winter climate (temperatures), though I'm not certain.  Nonetheless, yellow nutsedge (Cyperus esculentus) is the species Oregon growers should be most concerned with.

Control:  Neither tilling nor cultivation are effective, and both practices often make the problem worse.  Hoeing is not effective.  Translocated postemergence herbicides are necessary for complete control of root system and tubers, otherwise, new plants will emerge.  Contact herbicides are not effective (for long-term control).

Look alikes: purple nutsedge (Cyperus rotunda) and liriope (it takes a well trained eye to see and weed nutsedge from 'Big Blue' liriope).

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