Michael Mace mikemace@worldnet.att.net
Tue, 11 Nov 2003 23:22:08 PST
A few thoughts on Oxalis (and my apologies to those of you who have seen my
postings on this topic in the past):

--I have tried the South American species here, but they need careful
attention to water in my summer-dry climate, so I've given up on them.
Beautiful flowers, but too much work to maintain (especially when I was
having so much fun with the South Africans).

--I was lucky enough to get one of the Michael Vassar Oxalis distributions
several years ago, and they have grown pretty well ever since.  I have
probably lost about six of the 40 varieties in the collection, which is a
much higher success rate than I've had with most other genera.

The bulbs are growing in 8-inch plastic pots, in a mix of 50% perlite and
50% peat, with a generous handful of bulb fertilizer per pot.  The bulbs are
happiest if watering starts in August; some of them sprout at that time
regardless of the weather.  They grow throughout the winter, some blooming
in early autumn and others not blooming until late spring.  In summer they
are completely, 100%, bone dry, no moisture at all, exposed to about 50% sun
because I have too many pots and am too lazy to move them under cover.  They
don't seem to mind this awful treatment at all -- one of the many reasons
why I like them.

--They seem happier (bloom better and make more offsets) when repotted every
other year.  Every third years is too long for some of them, and they start
to dwindle.

--They do not like freezing.  Some species lose their leaves, some are less
damaged.  I was afraid that I had lost a lot of them one year when the tops
of the pots froze hard for several days, but the plants generally recovered.
I think it was
a close call, though.

--Some species offset a lot, and send little corms all over the pot.  Some
make a lot of offsets that cluster together.  And some don't seem to make
offsets at all.  Because of the tendency of some of them to send around
offsets, I would not grow them in a plunge bed.  But definitely you should
not avoid them -- they are, as a group, much less aggressive than (for
example) some of the Romuleas that are trying to take over my entire
collection.  And let's not even talk about certain Alliums...

--They don't set seeds.  I think I have seen one seed pod in the last five
years.  I don't know if they are just sterile, or they are not getting the
right pollinator.  I suspect the latter, and one of these days I'll try some
pollination experiments with a paint brush.  Anyway, because there are not
any seeds, they do not spread much in the garden.  I took some of my most
vigorously offsetting selections, and planted them among some rocks next to
a path.  They continue to come up every year, but they have not spread
anywhere else, even though there is open ground next to them.  If anything,
they are very slowly dwindling.  I think these things are generally very
safe in the
garden, at least here in my part of California.

--Rodents *love* to eat them.  This may be one reason why they don't spread.
In the first years I grew these bulbs, rats or mice dug into many of the
pots and almost cleaned them out.  I finally had to resort to putting a
layer of half-inch chicken wire in every pot, under the top inch
of soil.  This works quite well for me, although you have to cut the piece
of chicken wire wider than the pot, and then cram it into place so it's
firmly caught.  Otherwise the rodents will find a way to pull it out of the

--Nobody ever seems to talk about the interesting corms of many Oxalis.  My
favorites, O. obtusa, have a corm that's shaped like a wrinkled spindle --
tapered to a sharp point at both ends, dark brown or black, covered in
wrinkles, and very hard.  It's a wicked looking little thing, but also very

On the other hand, one of my other favorites, Oxalis massoniana, surrounds
itself with dense tufts of fibers that look like tiny wood shavings.
Presumably this protects them in some way.

--One of my favorites is one I know only as MV 4991 (that is a Michael
Vassar collection number).  It's a tiny tuft of foliage, maybe half an inch
high and an inch or two wide, topped with big white flowers with yellow
throats.  If it grew in the Himalayas, alpine enthusiasts would fall all
over themselves to create entire scree gardens for it, writing long articles
for the AGS Bulletin on its almost-impossible culture and elusive beauty.
Instead, this thing grows in the same old plastic pots as everything else,
gets cooked bone dry in the summer, and blooms reliably every year.

Who needs alpines when you have Oxalis?

--There appear to be many other interesting species of Oxalis, but I've
never seen them available.  For example, Barbara Jeppe's "Spring and Winter
Flowering Bulbs of the Cape" has paintings of beauties like O. tenuifolia
(long tufted stems with white flowers on top), O. helicoides (long spindly
stems with red flowers), O. convexula (looks like another alpine cushion
plant, with big salmon-red flowers), O. ciliaris (looks like an Oxalis palm
tree, with big pink flowers on top), and O. orthopoda (looks like a tiny
telephone pole covered in Oxalis leaves, with a white flower shooting out of
the top).  Where can we find these things?

San Jose, CA (zone 9, min temp 20F)

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