Oxalis in the ground

AW awilson@avonia.com
Thu, 04 Nov 2010 18:42:01 PDT

I was interested by your experiences with Oxalis in the ground as you had
initially claimed great success with them. I suspect that heavy clay may be
a problem there and I also suspect that planting bulbs under just a few
stones is not helpful. While I lost many also, especially ten yers ago, but
I have also had some success.

Clay soil problem is not present here except for a few patches in the garden
where it appears near the surface. I avoid those spots. After numerous
attempts with spare bulbs over the years, only a few species like O.
purpurea were found to survive rodent attacks if not protected in some way. 
With other species, the best way I've found for them them succeed is to
overlay bulb plantings with brick pathways, a technique that some iridaceous
bulbs showed me. Under bricks laid out with only tiny spaces between them,
the bulbs are protected from rodent digging. This is specially effective if
the bulbs are not close to the pathway edges or if the pathway has a brick
subterranean edging to discourage oxalis escaping outwards or rodents
digging inwards. This has worked for all species tried but it is less
successful for species with thick stems, like O. bowiea. The stems somehow
find a way to come up between the bricks.  The only penalties are that, once
in place, you must leave them for years and that you must be prepared to
limit your use of the brick pathway during wintertime when they are in leaf
and in bloom. They increase slowly in number and, as the species chosen do
not seed here, there is no escape issue to worry about. 

Your planting in rockeries did not, I suspect, provide adequate protection
against rodents. Here, chaparral pack rats are the worst offenders. Mice at
least eat the bulbs; pack rats use them in huge numbers to line their nests.
You could try much deeper planting or you could apply thick scree. I am
still experimenting with a grit and small stone scree mix. So far, it is
working, although it upsets me each spring at the start of dormancy to see
the rodents have dug up young bulbs that ended up near the surface by the
end of the growing season.

These methods might work in your area. I don't know. Much as I enjoy
pot-grown specimens I really prefer to have them planted out. Oxalis are at
their best in great numbers. But, pot protection for them incurs an enormous
amount of work, as it does for all my non-amaryllis or non-hyacinth family

San Diego

-----Original Message-----
From: pbs-bounces@lists.ibiblio.org [mailto:pbs-bounces@lists.ibiblio.org]
On Behalf Of Michael Mace
Sent: Wednesday, November 03, 2010 10:09 PM
To: pbs@lists.ibiblio.org
Subject: Re: [pbs] Oxalis in the ground

>> I would love to hear Mike's success with planting Oxalis in the ground.

Alas, the news is not good.

When I first got my Oxalis bulbs from Michael Vassar, I noticed that a lot
of them (especially the Oxalis obtusa varieties) produced copious offsets.
So I decided to try some of the extras in the ground.  I did it in two
locations:  A flat, well drained area with low competition from other
plants; and a rockery area in which I could slip the bulbs between stones.

Both locations do not get summer water.

In both areas, the bulbs bloomed well the first year, but faded away over
the next couple of years.  Meanwhile, the ones in the pots continued to

I don't know why the ones in ground failed.  Maybe they just don't like the
local soil (which is heavy clay).  I also know that the local mice love to
dig them up and eat them.  But they could not have dug up the bulbs that
were between rocks.  So I have a mystery.

People who think all Oxalis are invasive haven't tried to grow them in the

San Jose, CA

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