Max Withers
Sun, 04 Apr 2010 20:16:21 PDT
I have some Geissorhiza radians about to bloom for the first time. They have
been "about to bloom" for over a week. The weather has been mostly cool and
rainy. The Romulea monadelpha I mentioned a few weeks ago opened during the
day, but closed again at night -- and remained closed on rainy days, as did
Tulipa clusiana, though perhaps less definitively. Interestingly,
Calochortus umbellatus and various Freesias I've had blooming throughout
this period do not close either at night or during rain.

This mechanism, which must have a name that I would love to learn, is
obviously photosensitive, since the flowers close every night. But the
extended hesitation of my G. radians makes me wonder if anthesis can also be
sensitive to barometric pressure, since we have had some sunny spells during
the last series of storms.

Max Withers
Oakland CA

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