Media blends containing 25%, 40%, and 50% shredded tire rubber were compared to two commercial media, Baccto Grower's Mix and Ball Peat-Lite Mix, to evaluate its potential as a container medium amendment for container-grown greenhouse plants. Salvia splendens `Red Hot Sally' and Vinca rosea `Cooler Peppermint' grown in 25% rubber were marketable with growth similar to or superior to those grown in the commercial media. Exacum affine `Little Champ', Vinca rosea `Cooler Grape', Tagetes erecta `Discovery Yellow', and Begonia semperflorens `Vodka' grown in 25% rubber were of marginally acceptable quality. Plants grown in 40% or more rubber were shorter and chlorotic compared to those in the commercial media. Exacum affine grown in 40% or more rubber contained high levels of zinc, which may have been linked to the chlorosis and growth reduction. Rubber reduced media water-holding capacity, while cation exchange capacity and pH were not affected.