Perennial with annual aerial parts. The morphology of the inflorescence of this species varies from branched to simply glomerate- spicate, with the glomerules comprising few or many spikelets. The surface patterning of the achene is also variable, with smooth, tuberculate or trabeculate achenes occurring, sometimes even on the same plant. The same types of inflorescence and achene may occur in several species from all of which S. bulbifera is distinguished by its bulbous, woody and silicified culm bases which arise from a woody, horizontal rhizome with (usually) very short internodes so that adjacent culm bases are ± contiguous.
Perennial. Rhizome little more than the connective between swollen, contiguous culm-bases, or the internodes longer and culm-bases intervallate; scales light brown. Culms 0.12-1.10 m tall; bases swollen, woody, up to 12 mm thick, glabrous or hairy above. Leaves 1-5(9) mm broad, glabrous or hirsute; sheath with mouth concave, truncate, or produced into a short membranous tongue. Inflorescence unbranched or branched, 20-200 mm long. Glomerules 3-17, of 1-12 sessile spikelets. Bracts awned, equalling or up to twice the length of the glomerule, or the lowermost subfoliaceous, up to 30 mm long. Spikelets 4-6.5 mm long. Glumes 2-5 mm long, glabrous or hairy, awned, castaneous or dark reddish-brown. Achene obovoid to subglobose, 1.6-2 x 1-1.8 mm, glabrous, smooth or lightly or strongly tuberculate or trabeculate, grey or light brown.