We tested the host efficiency of an abundant non-native annual grass Parapholis incurva for the rare and endangered hemiparasite Cordylanthus maritimus subsp. maritimus. Flower production in C. m. maritimus was significantly less when P. incurva was the sole host (average 1 flower), than when the native perennial grass host, Distichlis spicata, was present (average 13 flowers). When C. m. maritimus was prevented from parasitizing either the native or non-native host, flower production results were similar to that of the non-native host (average 1 flower). Formation of haustoria did not differ between host identity treatments (average 270 haustoria per pot), but was significantly less in treatments that did not allow root contact between the host and hemiparasite (average 10 haustoria per pot). The “pseudo-host” effect of the non-native annual grass could result in high energetic cost to the endangered hemiparasite. Management decision-makers should factor in the costs of non-competitive mechanisms when prioritizing non-native species removal in areas with rare hemiparasites.