Getting through the first summer, an example

Jane McGary
Wed, 03 Mar 2004 13:02:12 PST
Jim McKenney asked,

>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.

It is often observed that many plants from alpine and arid habitats do not 
flourish in parts of eastern North America where summers are hot and humid. 
The converse is also true: plants from that region do not flourish, for the 
most part, in the gardens of the western third of the continent. One theory 
attempting to explain this is that the atmospheric humidity in the East 
prevents night cooling, even though the daytime temperatures on both coasts 
may be the same. The high night temperatures are theorized to be 
deleterious to plants that have evolved to "shut down" metabolically after 
dark, whereas those that have evolved with high humidity and high night 
temperatures are said to suffer from the extreme daily fluctuation 
experienced in summer-dry climates. This may relate to Jim's experience 
with air-conditioning his iris rhizomes.

Regarding the fritillaria bulbs, they should never remain out of the ground 
for very long. They do not have tunics and desiccate rapidly. When I lift 
them and keep them out for 3 or 4 weeks for my summer sale, I put them in 
plastic bags, not quite closed, with a handful of vermiculite. I cover the 
trays because exposure to light causes them to change color -- probably not 
too harmful. The past couple of years I've set up my bulbs in my dining 
room, which is cool and dimly lit. This means no formal dinner parties in 
August, but I can't get people way out here that often anyway!

Jane McGary
Northwestern Oregon, USA

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