Brian Whyer
Sat, 03 May 2003 05:43:09 PDT
> What are the hardiest species, and how cold are people growing
> tropaeolums? Which are most tolerant of moisture during winter?
> I live in nominally USDA zone 6 (NW Arkansas), with bouts of zone 5
> F/-26 C overnight). As usual, there are unexpected survivors, some
> the help of friendly microclimates (Gloriosa superba, for instance),
> just much tougher than the books say (the zantedeschias,
> But the ground never freezes deeply or for long, and so things with
> any degree of hardiness which like to be planted deeply stand a good
> chance if they'll tolerate winter moisture.

I have grown Tropaeolum tricolour for 2 years, in a pot on the bench, in
an alpine house that only occasionally goes below freezing. It looks a
bit lack lustre after a cold night but no damage so far. T. polyphyllum
I also have in the garden (in pots). Some survive some don't; I suspect
too damp rather than cold, or a combination of the two. T. pentaphyllum
survives in a pot against the south wall of the house, but as it is in
leaf all winter only flowers some years depending on the state it is in
by spring.
I am told sandersonia will survive in a sheltered spot, but cannot
confirm as I only grow it frost free. Similarly I have only tried
littonia frost free.

My pot of T. tricolour won an award this year in our local AGS group
show, as the members choice of best in show, but was ignored by the
visiting judge, as he did not consider it to be an alpine. Remembering
that the definition of an alpine or rock garden plant, for AGS shows, is
"one suitable for a rock garden of moderate size, or an unheated cold
frame or alpine house, and which will survive an average winter in the
area in which the show is held". Who knows what entries will be seen in
the future.

Brian Whyer, zone 8'ish, Buckinghamshire, UK

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