Oxalis triangularis? papilionaceae?

Ron Vanderhoff rvanderhoff@sbcglobal.net
Thu, 24 Sep 2009 18:00:34 PDT
So far as I know . . 

At the moment Oxalis triangularis supports two subspecies. O. triangularis ssp. triangularis usually has green leaves and are slightly smaller of the two ssp.

O. triangularis ssp. papilionaceae has somewhat larger leaves and are usually a shade of red or burgandy. This is the form that is usually seen in horticulture and there are many named selections.

Oxalis are a very confused genus taxonomically and many plants labelled as O. triangularis are probably not. Some are more likely the closely related Oxalis regnellii, which also has green and red leaf forms, sometimes even with two color shades on the same leaf. These are both soft, acaulescent, leafy plants, with very large (for an Oxalis) trifoliate leaflets. They form fleshy pseudobulbs.

O. triangularis is native to Brazil and possibly Argentina at rather low elevations, with year-round moisture and in organic soils. They are a challenge in my dry Mediterranean climate, going into stress and often dormancy with sustained temperatures above 80F, esp. with my low humidity. Triangularis is reportedly rather cold hardy, surviving in dormancy through winters at temps below freezing.

The plant you are calling Oxalis vulcanicola is a completely different species, with quite different characteristics. This plant is actually probably Oxalis spiralis ssp. vulcanicola and has many named and unmaned forms, often with colorful burgundy or caramel coloring. You will also see this plant under the name Oxalis siliquosa, but Dr, Alicia Lourteig, the leading authority on South American Oxalis, does not recognize this name, This is a caulescent plant with a noticeably semi-succulent, usually reddish colored stem. Both the leaves and flowers are very small. The flowers are yellow with red veins at the throat. It is quite easy to grow, but tolerates no frost. It also does not form a bulb or other storage organ and, thus in most gardens it is treated as an annual. It is native to South America as well.

Ron Vanderhoff

From: Leo A. Martin <leo@possi.org>
To: pbs@lists.ibiblio.org
Sent: Thursday, September 24, 2009 2:57:02 PM
Subject: [pbs] Oxalis triangularis? papilionaceae?


I have two clones of what I think must be the same Oxalis. One I bought as
O. triangularis (red leaves) and one as Oxalis papilionaceae (green
leaves.) I have in years past also bought the red one as O. vulcanicola. I
don't know what is the correct name. There are photos on the Wiki of the
red form as O. triangularis.

I have some in the house in pots and one outside under a patio cover next
to the hose bib. The one outside has survived the best, probably because I
have never forgotten to water it.

The plant isn't easy for me here in Phoenix. I have tried at least 10
times with it, starting with rhizomes and with plants. I have noticed only
about 10% of the rhizomes I have bought over the years sprout even though
they look fine when they arrive. The plant is prone to die if I repot it
while in growth. At first I would stop watering to let the plant go
dormant in the fall, but when I did this they always died and never
returned. In fact, even when they have wilted severely, they have never
come back.

Where in Brazil does this originate? What kind of habitat? Is it normally
a summer or winter grower? Is it particularly heat-intolerant? I know most
people think it's easy to grow and I'm trying to figure out why I have
trouble with it.


Leo Martin
Phoenix Arizona USA

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