Acceptable Oxalis

Christiaan van Schalkwyk
Wed, 29 Apr 2009 06:17:34 PDT
Hi all

Most of the winter growing south african species of Oxalis should be quite 
winter hardy. Some beautiful species and forms are found in the vicinity of 
Sutherland, which is regarded as the coldest place in South Africa, with 
daytime (winter) temperatures often below 5 degrees Celsius, and night 
temperatures well below zero(up to -15 !). (Over the whole year an average 
low of 3 degrees, and an average high of 20.5, according to

It must be remembered that very few Oxalis in cultivation will produce 
seeds, as it is not self fertile. However, when large quantities of various 
clones or collections of the same or similar species are cultivated, seeds 
might be produced. This could happen with Oxalis obtusa, the Oxalis 
flava/fabaefolia group, O. purpurea, O. luteola, etc., of which many 
different forms have been collected and are available. So if only one clone 
is grown no seeds will be produced - this is true even for Oxalis 
pes-caprae! (this, however, is not true of the weedy Oxalis of the 
America's - but then they are mostly annuals, and do not produce bulbs).

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.

Most Oxalis renew their bulbs each year, and various different forms of 
vegetative structures (stolons, rhizomes, runners, etc.) are formed, along 
which bulbs can develop. Species with these structures are more invasive 
than those who just quietly multiply where they are. Oxalis lawsonii (which 
is a spectacular species) is reported to produce bulbs up to a metre from 
the orriginal bulb in a single season. Many forms (not all!) of O purpurea 
(and similar sp.) do not form these structures, and will multiply locally, 
but do not spread as much or as quickly.

Unfortunately the underground system of Oxalis is not well studied, and the 
info that's available are not easily accessable. The easiest method to test 
an Oxalis' ability to spread is to plant a single bulb in a large pot, and 
check it the second year to see where all the new plants pop up in the pot. 
If it is in the centre (where the orriginal bulb was planted) it is not 
aggresive, if plants pop up all over the place underground runners or 
stolons have been produced, and the species are thus more aggresive.

And luckily most unwanted Oxalis succumb to a single touch of a brush dipped 
in a systemic herbacide . . .


----- Original Message ----- 
From: "Lauw de Jager" <>
To: "Pacific Bulb Society" <>
Sent: Tuesday, April 28, 2009 10:24 PM
Subject: Re: [pbs] Acceptable Oxalis

Dear all,
It is very hard to overcome the prejudice against Oxalis. I offer about 15
species and forms and try to be very careful not to offer species which can
spread dangerously. 

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