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Re: Re: CULT: late frosts

Well I guess this year will be a good test for them then.  Normal TB
bloom starts at the beginning of June which is about seven weeks from
now.  We have already had a week or so of nicer weather in the fifties
to sixties. But last week wasn't nice (down to 13 degrees one night) and
this week is another cold one.  Forecast is for 16 degrees tonight and
19 degrees on Thursday.

SE Manitoba

Linda Mann wrote:

Sandra, I wish I could tell you something precise, but it varies among
cultivars and, as Neil has posted before, is affected by preceeding
weather conditions, as well as stage of development.

Some cultivars start growing really rapidly as soon as warm weather
arrives and can suffer a lot of damage if temperatures then suddenly
drop very low, especially if it's been warm and moist for a week or so.

My rule of thumb has been if temperatures drop below 25 within 6 to 8
weeks of bloom, I expect damage to TBs (unless the plants are covered).
SDBs & IBs seem to be less affected or at least they can take a hard hit
closer to their bloom time.

Any fall greenery always gets freeze dried during the winter here, and
usually that doesn't affect bloom or increase disease problems.  Late
freezes, when plants are actively revving up for spring, can damage both
the current bloom and also really makes plants here more susceptible to

This morning, I noticed some tall foliage that was bent over holding up
the plant bed covers that was freeze dried on the side that was touching
the covers but was healthy on the underside.  Leaf spot is ravaging the
upper surface, but barely affecting the lower (I am sure it will
eventually affect the whole fan).

<Linda how big do the fans have to be before the frost (below 25 )
                  an iris's bloom for the season. Most of mine are less
than 4 inches high and
                  they have gone through a number of real cold days in
the low teens (lots of
                  "freeze dried" foliage).   Sandra   SE Manitoba>

Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
photos archives: <http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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