Burchardia umbellata (milkmaids) is native to much of Australia, with the exception of the Northern Territory (distribution map). To avoid growing under stressful dry summer conditions, Burchardia umbellata sends up its leaves from an underground tuber after autumn or winter rains, flowers in spring and then concludes its yearly cycle by producing its fruit before the worst of summer arrives.
Depending on whether local summer conditions are consistently harsh or variably harsh, different populations of Burchardia umbellata exhibit different summer dormancy characteristics. For example, where the onset of stressful conditions is consistent from year to year, dormancy is obligate; it will occur year after year at roughly the same stage of the plant’s life (i.e., the onset of dormancy is solely genetically determined). This confers the advantage of increased survival as a result of always avoiding stressful conditions, but loses the advantage of a potentially extended growing season which may mean larger growth, increased seed production or more storage of nutrients in the tubers. On the other hand, where the onset of stressful conditions is variable (e.g., in the highlands), dormancy is at least partially facultative–it can occur in some plants as a direct response to decreasing soil moisture, and not necessarily occur at a genetically predetermined stage of the plant’s life – these plants can benefit if an extended growing season occurs, but run the risk of sudden death if conditions change too rapidly (not all plants in these populations employ this strategy – some use the obligate dormancy strategy from above). For more on the topic (and to check to see if my interpretation is accurate), please see: Vaughton, G and M Ramsey. 2001. Variation in summer dormancy in the lilioid geophyte Burchardia umbellata (Colchicaceae). Am. J. Bot. 88:1223-1229.