Acceptable Oxalis
Jane McGary (Wed, 29 Apr 2009 10:45:31 PDT)
I'm glad to learn this new information about Oxalis, even if I can't
elicit an actual article!
Regarding winter-hardiness, it is a common misconception that
high-alpine species should be hardy in cold climates in lowland
gardens. If a plant, especially a geophyte, spends the winter under a
deep blanket of snow, it won't necessarily survive repeated freeze
and thaw cycles without snow cover during a temperate climate winter
-- especially if it's wet when it freezes. That's why many alpines
are grown under cover even though "perfectly hardy." It's not the
cold, it's the humidity....
It can also be difficult to maintain plants that have evolved to
undergo a very long winter dormancy, unless you're growing them in a
region with a similarly long winter. Wonderful alpines are grown at
or near sea level in countries around the North Atlantic, for
instance, and if you go up by the Arctic Circle, you can view such
plants in comfort without ever getting out of breath, because they're
just above the beach. I saw the same species at 1000 meters elevation
in Alaska and 4000 meters in Colorado.
This is Rock Gardening 101 -- I apologize to those who are both bulb
and alpine enthusiasts and know it already.
Christaan wrote,
All the "spreading" and "invasiveness" of (South african) bulbous Oxalis is
thus more due vegetative reproduction, and if Oxalis are kept in a pot, this
should keep the species where you want it to be. I say should, becouse
Oxalis roots can grow very deep, and if the pot is placed directly on (or
in) a suitable growing medium, the roots can go through the holes in the pot
and into the soil, and voila ! an escapee ! - most probably this is the
source of Jane's plants in the plunge sand.
Yes, it is; more than that, they will come UP through the drain holes
into other pots. In the case of little O. obtusa this is probably
harmless and can be charming: a pot of blue Juno iris surrounded by
pink oxalis flowers is very pretty. However, I have to comb all the
Oxalis tubers out of the other plants' roots when I repot them if
this happens. I'll try not to introduce the Oxalis to the bulb house
when I move, but it may be a lost cause.
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.
The South American one is more of a curiosity than a beauty, but that
could be said of a lot of "succulents."
Jane McGary
Northwestern Oregon, USA