Swordleaf Rush (Juncus ensifolius), sometimes known as Dagger-leaf Rush, is a perennial grass-like that grows along roadsides, streams, lakes, ditches, margins of springs and ponds, wet to seasonally-dry meadows, marshes, seeps, sandbars, foothills, planes, valleys, and mountain to sub-alpine sites. It is very distinctive from other grass-likes because of its unique, iris-like leaf structure.
Height: 8" to 24"
Solar Exposure: Part to full-sun
Bloom Color: Tan, black, or purplish
Bloom Time: Mid-summer
USDA PLANTS Database Link
Pics from https://plants.usda.gov/core/profile?symbol=JUEN