Fuirena and Lipocarpha could be confused at a glance, but in Lipocarpha the spikelets are shorter (< 8 mm vs. 8 mm or longer). Fuirena (except F. scirpoidea and F. longa, which have no leaf blades or blades < 5 cm) often has excurved scale tips. (F. longa, which we have never found in our area, is ostensibly a stable hybrid between F. breviseta and F. scirpoidea.) In Lipocarpha they are generally not excurved. Fuirena has bristles in addition to the perianth lobes. Lipocarpha has no bristles. In our Lipocarpha species the leaf blades are generally under 0.5 mm wide (ca. 1 mm in L. maculata) vs. generally wider in Fuirena. The Lipocarpha spikelet has just one flower, this associated with 1 or 2 (or 3 in species not in our region) leafy scales. There is just 1 stamen.
Fuirena umbellata is an unusual invasive exotic far larger than the other Fuirena species; it has a distinctive 4- or 5-angled stem.
1. Leaf blades absent...F. scirpoidea
1. Leaf blades present...2
2. Sedge to 6' tall, the stem > 1/3" in diameter at the base, 4- or 5-angled...F. umbellata
2. Sedge to 3' tall, the stem round, or if angular, < 1/3" in diameter...3
3. Perianth bristles shorter than perianth stipe (this is the only species in our area with the bristles so short, sometimes not apparent)...F. breviseta
3. Perianth bristles longer than the perianth stipe...4
4. Perianth bristles exceeding the achene height; spikelets mostly 5-8 mm long...F. pumila
4. Perianth bristles shorter than the achene; spikelets mostly 10-20 mm long...F. squarrosa