Peter Taggart is right that physiological drought through freezing is an important killer of some potted plants, and even those in the ground if it remains deeply frozen, but in all the cases of frozen amaryllid roots (and bulbs) I've seen it has been simple physical damage that has killed them. The duration of the freeze is irrelevant: one night's freezing solid of a pot will do the damage. John Grimshaw -----Original Message----- From: pbs-bounces@lists.ibiblio.org [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of Peter Taggart Sent: 08 October 2012 19:59 To: Pacific Bulb Society Subject: Re: [pbs] Cold hardiness of potted plants left outdoors in winter I think that there may be drought induced death in many plants if the roots freeze in a pot, whereas in the ground though the bulk of a tuber or bulb etc, including most of it's roots, may be frozen solid, the few roots which have their tips deep enough may keep the plant going. (While frozen there is very little moisture of a liquid form available to the plant.) I particularly feel that this may be the case with Cyclamen and rhizomatous Iris. This could equally well aply to the rootstocks of woody plants. Peter (UK) ----- No virus found in this message. Checked by AVG - http://www.avg.com/ Version: 2012.0.2221 / Virus Database: 2441/5317 - Release Date: 10/08/12