Acceptable Oxalis
Christiaan van Schalkwyk (Thu, 30 Apr 2009 01:12:17 PDT)

Hi all

These are comments from various posts on this topic:

Dylon:

I am curious what you mean when you say the bulbs renew each season.
Most or all of the SA bulbous spp. I grow (several dozen) build up
thick multi-season tunics around their bulbs, which seems to suggest a
'sedentary' organ that functions like a normal bulb.
What is radically different, though, is how the new shoots, somewhere
between the top of the bulb and the soil surface, produce that
season's root system anew. The bulb itself also has roots (from the
base) but these may be secondary?

Even most of these multi season thick bulbs form new bulblets inside the
tunics of the older structures. Many produce the new bulb lower than the
previous one (see eg. O haedulipes at
http://pacificbulbsociety.org/pbswiki/index.php/…),
and some even produce specialized contractile roots that actually pull the
bulbs deeper (see
http://pacificbulbsociety.org/pbswiki/files/…).
Other simply grow roots/rhizomes/runners, from either the top of the bulb,
the bottom of the bulb, or somewhere along the lenth of the stem, and form
bulblets along the way.
But this is a long and difficult subject, maybe I should write a wiki page
with illustrations on the roots and bulbs of Oxalis ? (Please - not this
week !). I think that one of the reasons why Oxalis bulbs rather quickly and
effectively change hemispheres are due to this renewal of the bulbs.

Do any other dicots have what could be called bulbs?

Thanks Jim for a beautiful answer !

Adam:

So for me to think about selecting anything to grow here in the
Chicago means that I'd need a list of desirable plants at Sutherland and
then I'd check to see which of those withstood our winters here. I'm sure
that most folks in the PBS can get away with growing almost anything from
South Africa. (No, I know it's not really true.) Might such a list be
handy to you , say-- in the form of plants available from a local nursery
there?

Dear Adam (and all other interrested parties)
Sigh and sad face :(
For most of it, we as South African do not appreciate the beauty, diversity
and potential of our Flora, (and on my side I do not understand "cold" that
well - a real "freezing" night means that the temperature dropped to -2
Celsius !). Very few indigenous species are available in horticultural
trade. For example, I've seen only five (!) species of Oxalis on sale at
nurseries, and NONE of these are South African. Specialized nurseries might
offer some SA species, Kirtsenbosch botanical gardens had about four (two
colour forms of O glabra, two colour forms of O purpurea) the last time I
was there, Cape seed and bulbs offer 27 (of which 3 are not SA) species, and
some other nurseries offer a few. There are more South African Oxalis
species available in trade overseas than in South Africa - see for example
the lists of Dylon Hannon and Diana Chapman. There are also some exellent
collectors, eg. Bill Baird, and Ron Vanderhoff. Some collectors out there
(many on this list) are more passionate about our heritage than what we are.
It would seem that Jim's ramblings are contagious.
Some of the Michael Vasser collections from around Sutherland might be
worth trying to get hold of (obtusa: MV2285, 2291, luteola 4960, meisneri?
4962, and Sp? 4729, 4767)

Jane:

That's why many alpines
are grown under cover even though "perfectly hardy." It's not the
cold, it's the humidity....

Luckily many SA Oxalis are used to winter rainfall !, and snow in the Little
Karoo . . .

In addition to the little Oxalis species of temperate South America,
there is at least one really big one, O. gigantea, which is a shrub
and I imagine there are similar manifestations in southern Africa.

No, sorry, all of the SA species have bulbs, only a few species can be
regarded as large, but they regrow yearly from the bulbs, eg. O comosa,
which can grow to a meter high.

Ron:
I forgot about the crown bulbs ! They are quite horrid in numbers, I have
counted up too 600 bulblets on a single plant of O. inaequalis. But I must
admit that my efforts too grow these into mature plants have not been
succesfull. O. inaequalis' bulblets at least stays in the pot when watered,
O pocockiae have light winged crown bulbs than can be blown around, and are
lifted up by the water

Christiaan