A  You have actually entered a fairly contentious area of debate with this question. I have asked many Dutch phalaenopsis growers whether warm water is necessary or desirable and almost every one tells me it is not. They quote research, presumably carried out in Holland, which found that, within minutes, the irrigation water had reached ambient greenhouse temperature. Most of their greenhouse water is drawn from holding ponds on the nursery, where it is a varying mix of rain and reverse osmosis water. Obviously there will be some fluctuation in water temperature from this source. I think it is important to remember that in Dutch watering, water is delivered precisely rather than turning on a sprinkler and waiting 15 to 20 minutes. Additionally, in British Columbia, there could be quite noticeable differences in temperature of water from a city supply when compared with stored rainwater.

My personal feeling is that warmed water is beneficial to orchid growth in cooler areas of the world. To achieve this, some hobbyists use elaborate solar warming devices or in-greenhouse storage systems. Those with small greenhouses may even use artificially heated water. If you choose not to warm your water, you may find an advantage in watering early on a sunny day, even delaying watering a day or two in winter to achieve this scenario. I add another water-related note of caution: Some phalaenopsis growers believe plants can be damaged and rendered susceptible to fungal and bacterial infection when watered overhead with cold water in the middle of the hottest days in summer. —Andy Easton,