Effects of Vernalization on Flowering in Ripgut Brome (Bromus diandrus)

Ripgut brome has a quantitative response to vernalization in relation to flowering. In greenhouse studies, cold treatment (5 ± 2 C) of 2, 4, or 6 wk shortened the vegetative period, but longer exposure did not further decrease the time required to flower. Plants vernalized as imbibed seeds for 8 wk took 17 d to flower following transfer from cold treatment to the greenhouse. Unvernalized controls flowered 53 d after planting in the greenhouse. Greatest total seed dry weight and vegetative shoot dry weight were produced by unvernalized plants, whereas lengthening periods of vernalization from 2 to 8 wk decreased both parameters. The percent of total seed dry weight to total shoot dry weight was significantly greater for vernalized plants than unvernalized controls. In field studies, ripgut brome plants established in the fall flowered sooner after resumption of growth in the spring than those planted in the spring. Plants seeded after April failed to flower until the following spring.