there must be a reason...

[tigrkittin]

Of all the plants in my office (I have 7 of varying types) the ones that need to be watered most often, and show the most distress if they start to get dry, are the two cactus plants. It somehow defies logic. Christopher, if you have some insight into this, do share

Comments

[istences]

Weird. All cacti that I know of, save for maybe a few bizarre and very rare exceptions use CAM photosynthesis, which is far and away the most water-efficient process.

Unless there is an apparent gouge in either of them or if they've been artificially-selected for a very thin cuticle for some odd reason (highly unlikely, the cactus would become fragile and/or soft), the most valid hypothesis I can draw without seeing them is that they're losing tons of water at night from transpiration. If my memory serves me correctly, CAMs only transpire at night, when it is much cooler in their semiarid/arid native habitat and the relative humidity is MUCH higher as the air that actually has water in it above the desert cools and sinks. This greatly reduces their water loss, at the cost of having less carbon to assimilate, which is why cacti grow very slowly.

Make sure the cacti are in complete darkness at night and in direct sunlight during the day so their rhythms aren't screwed up. When you leave each day, give them a light mist of water over the stem and cover them in plastic to afford them the higher relative humidity they're expecting at night. If that greatly cuts down on your watering, that'd support my hypothesis.

[tigrkittin]

cool, I will have to try that.

Hmm, the long weekends at work may be messing with them - since there are no windows in my office (or anyplace closer than across the hall) they have been staying in darkness from Thursday evening until Monday. So now that makes sense. I think they're OK overnight, but I will have to prep them better for the weekend.

Thanks!