pbs Digest, Vol 10, Issue 13
David Victor (Tue, 11 Nov 2003 11:02:05 PST)

I'd like to add my thanks to Robin for this week's introduction to a
favourite genus of mine: Oxalis. I've been growing them for the best part
of fifteen years and have (slowly) built up a reasonable collection of
them. What's more, many of the more attractive of them are flowering at
this time of the year. Add to that the fact that the weather so far this
Autumn has been very warm, sunny and bright, and they are flowering with me
as never before!

I grow a mix of mainly South African, but also South and Central American
species. Apart from a few from the far South of Chile, the rest are grown
in greenhouses. By far the greater majority are grown in a cold house
that drops to around minus 5C or lower in the coldest part of the
winter. I find that they can take a few degrees of frost without any
damage. If I think that the temperate will be particularly cold, I have a
further internal cover that can be pulled over them and the rest of the
winter flowering bulbs in the house. I grow the succulent oxalis in a
house that does not fall below freezing.

Altogether there's around 90 species in the collection, quite a lot of
cultivars. Around three quarters are Autumn flowering, mainly between
September and Christmas. They are all grown in my standard one litre pots,
in a mixture of a soil based compost and sharp grit/sand, roughly two to one.

Because of the particularly good weather conditions this Autumn, a number
of my plants have flowered properly for the first time and have been
particularly welcome. All three of them came to me under an O. species
banner or an incorrect name. Luckily, I have a copy of Salter's monograph
and have been able to tentatively identify them: I don't by any means find
this an easy task as I find Salter difficult to work with. However, I will
use those identifications here.

The first to flower was O. cathara (which came as O. species). This is one
of Section Crassulae, which have large scales at the base of the petioles,
such as O. flava. Also like that species, it has multiple leaflets, which
are long and thin. However, its flowers are much larger than any I have
ever seen on O. flave, having a corolla of some 3cms, pure white, with a
pale yellow throat. A truly beautiful plant.

The second was another O. species, which turned out to be O.
gracilis. This is a caulescent species, with the leaves on petioles a few
centimetres long and having a rather strange, flattened outline. The
flowers are reminiscent of O. massoniana, both in colour and shape.

The third came to me as O. massoniana and, indeed, looked rather like that
species until it flowered. However, at the point, the flowers that emerged
were almost identical to O. versicolor: white, with a pale pink edge to a
reverse petal edge, so it appears similar to a barber's pole. Another very
pretty species, which I have tentatively identified as O. heidelbergensis.

Incidentally, thinking about identification, many of you will grow O. 'Ken
Aslet', which has been identified under a variety of specific epithets in
the past. Last year, Mike Grant, the senior taxonomist at RHS Wisley
re-keyed the plant and confirmed it as O. melanostica.

Best regards,
David Victor