fall blooming pattern: was RE: Flowers of Crete

Jim McKenney jimmckenney@starpower.net
Fri, 04 Nov 2005 20:35:08 PST
Mary Sue wrote: The question or observation that I was raising, obviously
not very well, 
was that in California, at least the parts that are considered to have a 
Mediterranean climate, even though growth does not start until the 
beginning of the rainy season, the bulbs that I'm familiar with do not 
bloom in the beginning of this season, but at the end. There are of course 
exceptions that bloom soon after the leaves appear in the late winter, 
early spring, but a lot of them come into growth from October to December 
but don't bloom until May to June, sometimes after their leaves have 

Here's what I think (and remember, I'm an east coast guy who's never been
west of Texas so this should be a hoot). 

In general, I suspect that the answer has as much to do with the origins of
the flora of California as it has to do with the climate of California.

The Mediterranean basin has autumn blooming plants because it derives part
of its flora from areas where the initiation of the growing season was
triggered by rain patterns rather than by hot and cold cycles. Or maybe the
milder winters favored earlier and earlier bloom among plants which were
originally spring bloomers. [and here's a joke; maybe it's like those seed
companies which every year announce new varieties which are five days
earlier than last year's varieties. That has been going on for so long that
by now some of those varieties should mature before they are planted.]

California lacks autumn bloomers because its bulb flora seems to be derived
from plants adapted to the general North American weather pattern, i.e. cold
winters.  Unlike the Mediterranean basin, which derives part of its flora
from North Africa, Mexico does not seem to have contributed much if anything
to the bulb flora of California. Do any of the Mexican amaryllids,
gesneriads, or Oxalis even get into California?  

When plants adapted to cold winters and long summer growing seasons move
into areas with mild winters and dry summers, they face a big challenge if
their seeds germinate in response to warmth and moisture.  It seems to me
that adaptive pressures would favor those which postpone the ripening of
their seed. Why? Because if seed germinated late in the growing season, it
would soon die in the summer drought. All of those themidaceous plants and
Calochortus and others which bloom and ripen seed amid the dry grasses of
summer produce seeds which do not germinate during the summer. My guess is
that selective pressures favor postponement of bloom and seed ripening in
the Californian climate. And the same would be true in any
Mediterranean-type climate being populated by plants previously adapted to
cold winters and long moist growing seasons. 

It seems to me more likely that plants would achieve a one month delay in
bloom and seed ripening more easily than a four or five month advancement in
flowering time. Both might have happened, but I'll bet that selective
pressures favor the former over the latter. 

You may be wondering why fall blooming bulbs have not evolved in the
California climate. I think at least part of the reason here is that what we
think of as fall blooming plants, as I've said above, are not so much fall
blooming plants as they are plants which respond to wet/dry cycles. If
California had derived its bulb flora from Mexico, there probably would have
been fall blooming California bulbs. But apparently it did not, and so they
are not there - yet. 

How's that for oversimplifying a staggeringly complex issue? 

What do others think about this? 

Jim McKenney
Montgomery County, Maryland, USA, USDA zone 7, where we had a near
Mediterranean climate this year: dry summer and then drenching rain in

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