On 3 Mar 04 at 10:41, Jim McKenney wrote: > I have a general observation to make with regard to summer dormancy > in summer humid areas. I have attempted to bring some summer dormant > iris (oncos and onco hybrids) through our humid, hot summers by > digging them and storing the dormant rhizomes under cover but > otherwise in the open air in a shaded place. Something very > unexpected happens: these plants, which endure severe drought in > nature, shrivel up and dry out. Some frits seem to show the same > response here, others don't. > > With the iris, bringing them into the air conditioned house seems to > work better; the rhizomes remain hard and ironically don't dry out. > > This makes me wonder if the humidity isn't inducing the plants to > open their stomata and lose water - water which is not replaced by a > dormant or non existent root system. > > Is there a plant physiologist out there who can explain this better? An educated guess from a chemist: Something similar happens with cyclamen in pots. Unless you are careful to keep the soil slightly moist, the tubers wither during the summer. As a result, they are quite tricky to bring back to life, in many cases simply rotting away when our fall rains come. Rex Murfitt has told me of visiting a cyclamen guru in Britain who grows his plants in tall (ca. 12", 30 cm) drain tiles and keeps them sitting in a quarter inch of water all summer long. My guess is that these plants have a perennial root system which is constantly imbibing moisture, unlike, say, narcissus or crocus where the root system in annual and the bulb has no water uptake during dormancy. Certainly established cyclamen turn out to have a very extensive root system if you dig them up or decant them from a deep enough pot. -- Rodger Whitlock Victoria, British Columbia, Canada Maritime Zone 8, a cool Mediterranean climate on beautiful Vancouver Island