Temperature requirements for germination of buried seeds of Aethusa cynapium L.

Summary Freshly‐collected mature mericarps of Aethusu cynapium were dormant, but some germinated at alternating (16 h low/8 high) temperatures when the seed coverings were removed. Burial during winter increased percentage germination and the temperature range over which it took place. In late spring the range narrowed, first at low and then at higher temperatures, widening again in autumn. Moist storage at both low (4°C) and high (30°C) temperatures overcame dormancy, but exposure to 30°C inhibited subsequent germination at low temperatures. Germination of intact mericarps was consistently lower than that of de‐coated seeds. The cyclic change in dormancy status of the seeds appears to interact with the restricting effects of the seed coverings and perhaps other factors in determining the consistent pattern of spring emergence in A. cynapium.