Flowering and Growth Responses to Photoperiod and Temperature for Six Southern California Grasses

1. Growth and flowering responses to temperature and photoperiod were studied for six grasses that grow in the San Gabriel Mountains of southern California. The grasses included a native annual or shortlived perennial, California brome (Bromus carinatus Hook. and Arn.); two resident annuals, ripgut (B. rigidus Roth) and foxtail chess (B. rubens L.), both introduced from the Mediterranean area; three native perennials, California melic (Melica imperfecta Trin.), foothill needlegrass (Stipa lepida Hitch.), and pine bluegrass (Poa scabrella [Thurb.] Benth. ex Vasey). 2. All species grew well at 20⚬ C. day with 3⚬, 6⚬, or 10⚬ C. night temperatures. A 30⚬ C. day with a 3⚬ C. night restricted the growth of several species. 3. The flowering of California brome was little affected by photoperiod. 4. The resident annuals (ripgut and foxtail chess) and two native perennials (California melic and foothill needlegrass) flowered 10-20 weeks earlier under a 24-hour than under an 8-hour photoperiod. 5. Pine bluegrass flowered only under the 8-hour photoperiod and then only after 24 weeks when kept at constant daylength. 6. In a second series of experiments California melic and pine bluegrass could be made to flower simultaneously. After the seed of both species had been germinated and the plants grown under an 8-hour photoperiod for 3 months, they were transferred to a 16-hour photoperiod, where they flowered in 5-6 weeks.