Slender Spiked Rattlepod is an erect annual herb, growing to 1-2 m tall. Stem and branches are stout, quadrangled and hairy. The species name leptostachya means, having slender spikes. Alternately arranged leaves, 8-10 cm long, are oblong-lancelike, and nearly stalkless. Leaves are membranous, and have rounded bases. Yellow pea-like, short-stalked flowers occur on slender spikes.