With rising feed prices and concern over competition between humans and animals for land utilization, forages that can be grown with lower resource utilization provide an opportunity for use in ruminant rations. One such potential crop is cup plant (Silphium perfoliatum), a perennial flowering plant that has low agronomic inputs and can be grown on marginal land. The objective of this experiment was to compare cup plant varieties to corn silage (CS) in vitro to isolate genotypes that may be pursued as forages for ruminants. Twelve genotypes of cup plant (varieties 1–12) were tested in batch culture with CS as a control. Substrates were dried at 50°C for 48 h and ground to 2 mm particle size. Strained rumen fluid was mixed with McDougall’s buffer in a 2:1 ratio of buffer to rumen fluid. This inoculum (50 mL) was added to 125-mL serum bottles containing substrate (0.5 g) and one bottle containing inoculum alone. Sealed bottles were incubated in a shaking water bath at 39°C for 24 h. At 5, 10, and 24 h of incubation, gas production was measured by water displacement. Contents were transferred into 50-mL containers and dried at 100°C for 48-h; remaining dry matter was used to calculate dry matter disappearance (DMD). Measurements were replicated during 4 24-h periods. Means were compared against CS using the Dunnett test in PROC GLM of SAS 9.4. Differences were declared significant at P ≤ 0.05, and tendencies were noted at P < 0.10. No differences were detected between any cup plant varieties and CS for gas production (P ≥ 0.70) or DMD (P ≥ 0.65). Three cup plant varieties were similar to CS in pH at 24 h (P ≥ 0.26; pH = 6.38, 6.48, 6.5, and 6.49 ± 0.042 for CS and varieties 7, 8, and 11, respectively). Four cup plant varieties (variety 4, 9, 10, and 12) tended to differ in pH from CS (0.1 ≥ P > 0.05; pH = 6.54, 6.54, 6.54, and 6.54 ± 0.042, respectively). The remaining 5 varieties had different pH from CS, ranging from 6.54 – 6.60 (P ≤ 0.05; SEM = 0.042). These results indicate that varieties 7, 8, and 11 may be more suitable candidates than the other varieties investigated for future research examining the inclusion of cup plant in ruminant rations.