Several species of annual sedges including rice flat sedge (C. iria) and compressed sedge (C. compressus) can infest container stock.  In contrast to yellow nutsedge, these species spread strictly by seed.  Flowers are green or yellowish-brown.  Seeds germinate spring through summer, flower late summer through early fall, and then die after frost.  Stems are triangular and plants grow best in wet sites in hot weather.  Annual sedges have a clump (or tillered) growth habit and frequently have red roots, but lack the rhizomes and tubers seen in yellow nutsedge.  Annual sedges are easier to control than perennial nutsedges.  Several preemergence herbicides are effective on annual sedges and handweeding is easier and more effective than with nutsedge.