pbs Digest, Vol 10, Issue 13

David Victor davidxvictor@mailblocks.com
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 

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