Tony, Good Stuff. I suspect a little oedema might be welcome if it was the result of a break in the drought. I was down looking at my property and ammazed at how well the trees seem to be withstanding the dry conditions but read in the Carolina Gardener that I should expect many to die next spring. --- Tony Avent <tony@plantdelights.com> wrote: > Bob: > > I don't have an old wife, but will tackle these > tales as it relates to > agaves. We have two water issues that cause severe > foliar damage. If > we have several days of rain in the fall or early > winter as the growth > is slowing, followed by bright sun, we can get > terrible leaf scorch due > to Oedema. . > http://plantclinic.cornell.edu/FactSheets/oedema/…. > > > The other water related damage occurs after either > an ice or snow storm > that leaves frozen water on the leaf surface. When > the sun reappears, > the tissue beneath the ice is scorched due to the > magnification of the > suns rays through the water. No damage occurs where > the ice or standing > water is in the shade. Over the years we have seen > such damage on other > plants, but none as severe as we see with agaves. > > Tony Avent > Plant Delights Nursery @ > Juniper Level Botanic Garden > 9241 Sauls Road > Raleigh, North Carolina 27603 USA > Minimum Winter Temps 0-5 F > Maximum Summer Temps 95-105F > USDA Hardiness Zone 7b > email tony@plantdelights.com > website http://www.plantdelights.com/ > phone 919 772-4794 > fax 919 772-4752 > "I consider every plant hardy until I have killed it > myself...at least three times" - Avent > > > > Robt R Pries wrote: > > Jonathan wrote; > > > > " It doesn't really make sense, as I think about > it, > > and I suspect you'll > > agree, that the sun's heat would lead to > increased > > chilling of the > > leaf under where the waterdrop was located--it > > wouldn't evaporate any more > > rapidly than the sun's heat caused it to > vaporize." > > > > I am a bit on shaky ground since I am not a > physical > > chemist, but as I understand the phenomenon. > Sunlight > > can increase evaporation and although there is a > > direct relationship between light and evaporation, > > calories may be drawn from the surrounding > > micro-environment and not just the sunlight as the > > water changes state. Since there is a > proportionally > > huge consumption of calories required some of > these > > may be drawn from the leaf. The sunlight may not > be > > the only source of heat for the evaporation and > may > > facillitate the process by affecting surface > tension > > and other factors. Thus the immediate area of the > leaf > > may be chilled because of its donation of heat to > the > > process. Perhaps we are both saying the same > thing. > > > > > > _______________________________________________ > > pbs mailing list > > pbs@lists.ibiblio.org > > http://www.pacificbulbsociety.org/list.php > > http://pacificbulbsociety.org/pbswiki/ > > > > > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/ >