Rumex vesicarius (Ruby dock; subgenus Acetosa, section Vesicarii, family Polygonaceae) shows fascinating ways of controlling and staggering seed germination throughout the year. Seeds within the large inflated fruiting valves (fruits) display variations in their ability to germinate, which are related to the time of the year and depend on the presence of light. Perianth-imposed dormancy appears to undergo one distinct seasonal cycle under laboratory conditions. Our results suggest that germination is best during the autumn and winter months but poor during the rest of the year. In the natural environment (fruits either remain on the soil surface or are buried) dormancy release may be occurring several times during the year under appropriate light, temperature and moisture conditions. Preliminary experiments indicate that the fruiting valves produce chemical substances that inhibit seed germination, and their break down appears to be affected by light.