This study analyzes the influence of temperature, light conditions, seed age, and seed position in the fruit on germination of four Coincya taxa endemic to the south-central Iberian Peninsula: C. rupestris subsp. rupestris (two populations), C. rupestris subsp. leptocarpa, C. longirostra, and C. monensis subsp. orophila (two populations). The first three taxa are endangered. Germination was considerably lower in darkness than with a photoperiod in all taxa analyzed. Freshly matured seeds of C. rupestris subsp. leptocarpa and C. rupestris subsp. rupestris from main population showed primary dormancy, failing to germinate at any temperature or light condition tested. In the other taxa and populations analyzed, fresh seeds showed conditional physiological dormancy, germinating at low and middle but not at high temperatures (32/18 °C). In most taxa and populations, germination capability increased with seed age, and dormancy was finally broken, which suggests that Coincya taxa have non-deep physiological dormancy. The hypothesis that seeds can be induced into conditional dormancy with seed age was confirmed in a population of C. monensis subsp. orophila, where seeds lost the ability to germinate at 5 °C from the fourth month of dry-storage. In most populations tested, short-aged seeds (≤2 months) showed a more pronounced dormancy level when they were collected from the valvar dehiscent portion than from the indehiscent beak. However, the hypothesis that thick-beaked taxa have beak seeds with higher germination than seeds from the valvar portion cannot be accepted as a general trend.