Re: hardiness of Sauromatum
My personal experience may not be relevant, as I live in the UK, but I have
found it much hardier than gardening manuals say. For instance, the Royal
Horticultural Society's A-Z Encyclopedia of Garden plants gives "minimum 5
degrees C (41 degrees F), while my plants stand several degrees of frost.
First I planted surplus tubers at the base of a wall that stays warmer and
drier than the border. When they survived and multiplied I then tried them
in the open ground and last winter (which was pretty mild though of course
with some brief frosty spells - and loads of rain) they came through again,
no problem. I live in Norfolk, which is not a particularly warm area of
Britain. Also we don't have hot summers, but they grow very nicely just the
same. Plants currently have leaves 60cm (2ft) across, with leaflets 30cm
(12in) long, on stems 60cm (2ft) tall. From a single tuber, most plants now
have four or five other leaves in addition to the main one that develops
after the inflorescence withers. They have infructescences developing at
ground level too.
I have also found that plants grown in the open ground, rather than in pots,
get much bigger, stay much healthier, and multiply faster. They form very
handsome clumps of leaves and in my view should be much more widely grown as
garden ornamentals. They are also happy in full sun, which most arisaemas
don't like. Even in areas that have a hard freeze, they could be treated like
other bulbs, and lifted in the fall.
Next winter I'll try to keep records of actual temperatures.
Hope this helps.