BULBS. Dormancy in many geophytes is an annual occurrence, even in those native to equable climes that have much relatively little seasonal variation in temperature. The growth cycles can be quite complex in some species. For example, the mother bulb may be in full growth and yet the daughter bulbs (or corms or rhizomes) remain dormant. Then as the mother bulb completes its growth cycle and senesces the daughter bulbs may begin growing even while attached to the mother bulb (acidanthera definitely follow this pattern and I believe that the same holds true for many amaryllids that I grow). Chilling and dormancy. Tulips. Some tulip selections are well known to require over 1000 hours below 50 F (10C) to get proper shoot development of the mother bulb (the one purchased from the nursery). Four out of the last 6 winters in Davis (mid November through February) we have been shy of that number and consequently I have given up on the beautiful, tall cut-flower tulips. The thing to do is to refrigerate bulbs for 6 weeks shortly after purchase and then plant them. This works for relatively small quantities of bulbs but not the large numbers I had in mind for cut-flower purposes. Narcissus. It's clear that most selections of narcissus require considerably less chilling than tulips to develop excellent shoot systems. My first Earlicheer this year in Davis, a tazetta variety that I obtained from Bill Welch, were at anthesis in late November when we had little more than a hundred hours of chilling. Some of Rees' data for 'Golden Harvest' narcissus (The Growth of Bulbs, A. R. Rees, Academic Press, 1972) show that as few as 600 hours of chilling at or somewhat below 48 F (ca 9 C) suffice for early and high quality flowering. I've been hard-pressed to find exact chilling data for other species and would appreciate help from the forum. Ethylene and ethylene generating treatments and dormancy. Ethylene gas at low concentrations (20 ppm) reduces the length of or quickly breaks dormancy in a number of geophytes. Ethephon (2 chloroethane phosphonic acid), a water-soluble ethylene releasing compound can substitute for ethylene gas. Immersing bulbs, corms, rhizomes, etc in ethephon solutions, with say 0.1 active ingredient, would be the preferred treatment technique for most of us. I cannot find a source for ethephon on the web so this may no longer be a useful tool to gardeners and nurserymen. Triteleia laxa (Queen Fabiola), responded to a 7 day treatment of corms with 20 ppm ethylene with a 30 day advance in corm sprouting and an 80 % increase in number of florets per inflorescence (and a 25 % increase in daughter corm weight). Smoke from burning foliage releases ethylene and promotes earlier sprouting of the bulbs and earlier flowering. This practice was developed by iris growers in Japan to control disease, then found to reduce the dormancy period, and then the research was done revealing the release of ethylene during burning. Other problems. In adequate chilling is not the only thing that goes awry when I have attempted to naturalize the large, cut-flower tulips. Excessively high spring temperatures, a frequent problem in the Davis area and much of inland California, cause early foliar senescence of some selections that I've grown, preventing adequate photosynthesis during the post-anthesis daughter bulb-filling stage. Small daughter bulbs produce small or no flowering shoots the following spring. High temperature after-ripening and dormancy. Many geophyte species are stored by growers at temperatures in excess of 90 F ( 30+ C) immediately after lifting to promote sealing of base plate or other wounds incurred on lifting. For some species this period is as short as a few days, but in freesia the optimum storage time is on the order of 10 to 13 weeks, much longer than required for healing of tissues. Something else is changing in the corms but I find no literature describing what is happening, physiologically speaking. I've encountered high temperature-induced dormancy frequently in alstroemeria hybrids and some species. When soil temperatures are at or near 80 F (26 C) most alstroemeria cease growth. For some resumption of growth is almost immediate when temperatures are reduced to 60 F (14 C), but in A. pelegrina and other species (see below) growth did not resume for months after the soil temperatures were lowered. Also, in A. ligtu, A. magnifica, A. aurea, A. diluta, A. kingii and others the rhizomes become dormant shortly after anthesis or if the soil temperatures are elevated. Chilling the rhizomes or cooling the soil does not break this kind of dormancy; but two to three months of patient waiting works wonders.