Variation between Emex australis populations in seed dormancy/non‐dormancy cycles

Seeds of four Western Australian accessions of Emex australis were stored outside and their germinability tested at 4–6 week intervals for 22 months. Accessions showed cyclical behaviour in germinability, with peaks in autumn/early winter and troughs in spring/summer. There was considerable variation between accessions in dormancy/non‐dormancy cycles, but when plants from accessions with contrasting cycles were grown in a common environment, the cycles shown by their seeds were virtually identical. Thus, the parameters of seed dormancy/non‐dormancy cycles in E. australis appear to be under environmental control. Only part of an E. australis seed population demonstrated cyclical changes in dormancy status, in contrast to many other annual species whose entire seed populations undergo such changes. Populations also contained individuals which were either continuously dormant or continuously non‐dormant following a period of after‐ripening. The latter seeds give E. australis the flexibility to recruit opportunistically after summer rainfall events in mediterranean‐climate environments.