Question
I see your very first question for Feb is about our dear friend, Oxalis. Maybe you can help with mine on the same subject: Is the yellow oxalis that is covering our hills (see Bernal Heights et al) and sprouting in our gardens now a non-native variety? Is it in fact from South Africa as local legend has it? And what exactly is its genus/species? I've researched (and argued about) this issue with many but cannot find a definitive answer. Thanks for any help!
Ed
San Francisco
Answer
This pretty little non native is now considered an invasive weed threat. It is indeed from South Africa and is known as Oxalis pes-caprae (Synonym O. cenua). It does not spread by seed but asexually by lateral roots and many small bulblets that are formed along it's tap root under the soil. At least there is no evidence that it sets seed. It spread first to the Mediterranean in the 19th century and then to the Americas. It was mentioned in Bailey's Horticultural Manual in the 1930's after it was probably collected for use as an ornamental. There is no mention of it being in California prior to 1925. It was first noticed (or rather recorded) to be prominent in southern California orchards and vegetable fields in 1951. How did it spread? Bulblet contaminated soil on shoes, tractors, tires, tools, or innocently planted by people who dug it up to plant in their yards. It could have been spread by imported bareroot trees. In any case, it certainly has taken "root" along our coast.
Share this post
