CULT: cold & this n that

Boy, Linda.  If you are right about 25 degree cut-off, then I can expect a
whale of a lot of damage.  My outdoor thermometer (uncalibrated) showed 18.8
degrees minimum Monday morning.  We had dropped below 32 soon after sundown,
so there were looooong hours of freezing temps.

I'm sure my irises are not as far along as yours, but I have a comment about
the 25 degree cut off.

I don't know how this works yet in NC, but in Idaho I know it made a lot of
difference in how much cool-down time occurred ahead of a hard freeze.  Irises
showed little damage from temps deep into the lower 20's even right into bloom
time if they had adequate time ahead of the freeze to chill.

Apparently there is a natural "antifreeze" character in plants that allows
them to tolerate freeze.  I imagine it has to due with the ratio of soluble
solids to water in the cell sap.  Some plants may produce extra sugars or
something like that, or else a reduced uptake rate of water from the soil, or
both,  giving the cell solute a lower freezing point.  Bearded irises seem to
have this ability right along with pansies and winter cabbage..

I know that Monday morning, even with the temp as low as it was, the iris
foliage looked perfectly normal after the air warmed up.  In rapid hard
freezes, such as those we've had with an abrupt drop from 70-ish temps into
the low 20's in a matter of hours, the foliage has looked awful the next day
with uneven darker green areas having an almost glassy look to them.  Even
though those scalded-looking areas healed, they never recovered fully.

Monday daytime the irises here showed none of that.  We had two or three days
of good chill ahead of this frost, and haven't really had a high temperature
here yet at all.  A week or more ago it did get into the upper 60's for a few
hours a couple days.  That's all.

It is going to be interesting to see just how much damage I got.

Neil Mogensen  z  7  western NC

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