Phisherman wrote:
I'm in east TN and have a rather large cactus collection (about 100
specimens). I have a place that gets full (brutal) sun and would like
to plant a cactus that survives East Tennessee winters. I have an
American cactus (from the USA west coast) which I propagated and tried
to toughen it up, but I think it may have died due to frost. I see
large cactus growing in various places (Knoxville, Oliver Springs, Oak
Ridge, etc) that have been growing for years and they produce summer
bloom. Can anyone tell me what cactus will grow outdoors in my
location?

There are numerous cacti, almost all Opuntia of one sort or another, which
will grow in Knoxville. Getting a pad or two to propagate should prove to
be no problem if you approach the owner in a friendly way. Or you could buy
some starts. One source is:

http://www.coldhardycactus.com/Pages/Opuntia.htm

I've never used them but given the prices it would be hard to go wrong.

Cacti grow all the way up into Alberta, Canada IIRC. Some of the prairie
cacti are totally inconspicuous, growing very close to the ground and
protected by the surrounding plants. I have collected cacti in the wild far
up into the mountains in Utah, far above the snow line. All of those were
Opuntia also.

--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com