What promotes blooming?

Jane McGary janemcgary@earthlink.net
Sun, 14 Oct 2007 10:09:08 PDT
I haven't been following this thread too closely because I know that I will 
never get Nerine or Crinum to flower here, but I should mention, in 
addition to absolute temperature in terms of daytime highs, many plants 
seem to be sensitive to temperature FLUCTUATION. In areas where atmospheric 
humidity is low in summer, such as the American West (especially outside 
large cities, which experience a "heat island" effect), the difference 
between daytime and nighttime temperatures is usually much greater than in 
areas with high atmospheric humidity, such as North America east of the 
Rocky Mountains. As a result, plants evolved in humid environments 
experience almost nightly lows to which they aren't adapted, and so we in 
the West often notice that plants from the East dwindle away over a few 
years, however much we irrigate them in summer. I find the same to be true 
of many plants from Japan. In respect to bulbs, this fluctuation would be 
moderated within the bulb itself, but if the leaves of a summer-growing 
bulbous plant (which are making food for the bulb and flowers) suffer a 
"dormancy trigger" every night when the temperature drops 30 or 40 degrees 
Fahrenheit (as it does where I live), this may affect bud formation.

I have no trouble flowering bulbs whose leaves are dormant in summer, even 
those from warmer climatic regions near the shores of the Mediterranean.

Jane McGary
Northwestern Oregon, USA

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