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Re: [iris] Re: REB: climate (was reverse stripes on iris-photos

  • Subject: Re: [iris] Re: REB: climate (was reverse stripes on iris-photos
  • From: DFerguson@cabq.gov
  • Date: Tue, 3 Aug 2004 11:43:43 -0600

Hi Bill,

I'm not even going to try to get into plant physiology here; I'd probably
get it all wrong anyway.  It varies so much with the type of plant under
discussion anyway.  Just some random observations from New Mexico.  And,
no, I'm no expert on reblooming - hardly even close.  I've only bought one
Iris in my life simply because it is a rebloomer (Frequent  Flyer),
otherwise rebloom  is just a nice bonus when it happens.  So, I haven't
made a study of it.

I looked up Albuquerque's mean annual temperature, and according to one
data source, it is 56.8 F.  So, I suppose that technically makes us cooler,
but nights are cool due to low humidity.  Humidity is very low and there is
usually little or no cloud cover.  My average highs all summer (from
sometime in May to sometime in September) are in the 90's without much up
and down fluctuation, so it bakes in the day.  The warm up in morning is
not gradual either, it is a rapid jump.  Surface soil temperatures of 180 F
and higher are not unusual by mid afternoon, though I don't have any good
sampling data to quantify this.  Albuquerque's average high for July is
92.3 F, but most of the area is somewhat warmer (that's up on a hill at the
airport, out of town).  The average low for July is 64.7, but low lying
areas are often 5 or 10 degrees cooler (makes ripening Tomatoes a slow
process in summer).

For January the average low is 23.8 and the average high is 47.6, but low
lying areas are considerably warmer in day and colder at night.  It varies
a great deal with the specific location.

I think there is a lot more important than mean temperatures.  I didn't
check, but San Francisco or London might have a similar mean, but totally
different climates otherwise.  It seems to me that highs and lows are very
important, as is humidity and soil quality.  I can't imagine that all of
these wouldn't affect reblooming.  I've noticed that even if highs are
consistently high, cool night time lows allow many plants to survive or
even thrive, where they wouldn't if nights were warmer.  Of course, this
varies with the plant; other plants like it hot at night in summer, and
despise cool nights.

>From our mean temperature, you might guess that northern Iris like I.
variegata would thrive here; however, high temperatures and low humidity in
daytime make them difficult to establish and tricky grow unless you give
them some shade, extra water, better than average soil, etc.

Reblooming Iris seem to (in general) rebloom fairly well here, but I've
always assumed that it is because our hot dry days in summer tend to put
them into a deep dormancy.  This seems to help trigger a rebloom (at least
in some) when it cools down some in August or September.  I hardly ever see
Iris flowers between early June and September here, but September to
November often have good shows of flowers.  On some cultivars, some years,
the fall flowering almost rivals the spring flowering.  The few that do
bloom in summer usually do so sparingly, and they tend to be some of the
ones that are almost everblooming in some climates (s. CA, or in a
greenhouse) such as Eleanor Roosevelt, Frequent Flyer, or Immortality.
These seem to be ones that don't even try to go dormant, unless you force
them to with extreme conditions.  They do pretty much shut down in summer
(and winter) here, but there is an occasional fan here or there that tries
to defy the conditions.

Well enough of my drivel for now,


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