CULT: TB growth habits

I had an offlist email about growth habits & thought others might be
interested in the topic:

<Do you see distinct growing habits of varieties?  Here [Louisiana],
some start growth in the fall and grow thru the winter.  Some start
growth in late winter (Feb. here), some in March, some in May...>

Yes, in fact, this was something that I was looking at a lot back in the
middle ages before finding the internet in 1996, when this forum was
born.

I see three different growth habits here:

1) Those that drop their leaves in summer drought (keep in mind that I
have extremely gravelly soil) AND after continuous cold winter weather
sets in.

2) Those that stay green year round and try unsuccessfully to grow all
winter in every warm spell and have repeated foliar damage.  These are
usually rapid growers & probably make fantastic numbers of increases in
more consistent climates.

3) Those that stay green year round, but have something that keeps them
from experiencing much foliar damage unless temperatures get a lot
colder than we've experienced in recent winters. The 'winter hardy'
rebloomers mostly fit in this group.

Within the first group, there are some that begin growing earlier in
spring or will grow all through the mild winters we've had lately.   I.
pallida has this kind of growth here.  Maybe this should be 1a)

1b) Others, such as SULTRY MOOD, don't start growing until spring warm
weather is here for sure.  I was astonished to see SM stay green and
growing all summer in a partly shaded bed where I was watering other
things.  Sure doesn't do that out in the rockpile!

I think that some within this group seem to be regulated by daylength,
while others are regulated by temperature.  I.e., some always start to
grow in mid spring, regardless of temperature, so would be early
blooming some years, mid or late in other years, responding to our
vagaries of weather.  Others would always bloom (or try to bloom) in the
same sequence, regardless of the weather.  I haven't taken notes on
this, so am not sure.  But it would explain why some cultivars bloom at
different sequences in different climates.

In 1996, when we were still having real winters here, I wanted to grow
only the (1b) types.  The (3) types that I knew about were all
rebloomers that bloomed so early in the spring and so late in the fall
that bloom would either be killed completely or severely damaged.

Nine years later, I've become more interested in roots as the main key
to whether or not something will thrive here.  The irises that thrive
here make new roots <fast>.  If a rhizome doesn't start producing new
roots within 2 weeks, it probably won't do too well here.  The most
successful cultivars are those whose big fat roots are slow to dessicate
as well as being able to produce new big fat roots quickly.  They also
grow deep - 2 ft straight down is best. I have great hopes for ABOUT
TOWN - in its trip from Oz, it had already started growing new roots in
the shipping box!

I have also found that some 'evergrowers' can rebound from quite a lot
of winter damage and still do ok, and have found many rebloomers that
bloom late enough in spring and early enough in fall to do ok here.

Does this match experiences of irises that thrive in other climates &
soils?

--
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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