Mediterranean gardeners´ would agree to hate it´s the Bermuda Buttercup (though it´s not from Bermuda and nor is it a buttercup!) also known as Cape Sorrel or Sourgrass – oxalis pes caprae. On the basis of better the devil you know, let´s take a closer look at this plant and how to control it.
The sorrel family is one of the biggest in the plant world with some 850 family members and they´re almost as widespread and insidious as Coca Cola. Only the poles are not invaded by oxalis.
I know many people, newly arrived, who have carefully dug up clumps of the vivid green clover-like leaves with the striking yellow flowers and carefully replanted them in their garden. You can understand the mistake because there is little more stunning than a sheet of yellow Bermuda Buttercup marching through an ancient olive grove under blue winter skies. Indeed that was how it was first introduced to Europe, way back in 1757. Plant collectors brought it from the Cape area of South Africa and introduced it as a stunning ornamental to gardeners in London. For the next century it spread through Europe, particularly Mediterranean areas where the climate suited it well. Nowadays it grows in southern Europe, north Africa, south-west Asia, Pakistan, India, Australia, the south island of New Zealand, China, Japan, the states of Florida, California and Arizona in the U.S. and western South America – quite a spread. But then none of you gardeners will be surprised by that, I´m sure! In many of those areas it is classed as a noxious and invasive weed.
For us, it arrives with the rain and disappears with the heat but, in the meantime, it swamps and romps! So, what´s the answer? Well, very persistent hand weeding will work – over years – but it is, admittedly, very tedious and impossible over very large areas. Tackle it when it´s just big enough to grab and after rain so that you can try and extract the entire root. Once it matures it sets little bulbils which help its spread. But, if you can´t face that, a glysophate-based weedkiller is the answer. Try not to spray as that is very destructive to our environment and sure death to other plants. The best method where the Bermuda Buttercup is entangled in other plants is to get your gloves on. Firstly, a latex pair to protect your skin, with a cotton pair on top. Dip the tips of your gloved fingers in a 10% solution of the glysophate with a squirt of washing-up liquid to help sticking and carefully drag your fingers across the yellow invaders, carefully working around valued plants. The cotton gloves absorb the weedkiller well and the tiniest touch will kill the Bermuda Buttercup. It will be absorbed through the system of the plant and will kill leaves, stems, roots and bulbils. Some effect will be seen after a few days but it can take 2 weeks to completely kill the plant. Don´t be tempted to make a stronger solution – it´s dangerous and counter-productive. If it´s too strong, the top growth will burn off immediately before the product has time to be absorbed through the plant and it can then regrow.
There are two other solutions. Let pigs or turkeys graze through your buttercups – they both love it and eat the bulbs too – they´re surprisingly efficient at clearing large patches.
But the best answer is to eat it! The entire plant is edible with a surprisingly good sharp lemon flavor. The name sorrel is from the High German word sur meaning sour and oxalis is from the Greek meaning pungent. Both names refer to the sharp flavor of the oxalic acid found in the plant. Sorrel is a herb with a long – edible – past and our Bermuda Buttercup is no different. Admittedly, too much oxalic acid is bad for you causing kidney problems and leaching of calcium but you would have to be force-fed on it for months for this effect to be seen. Only if you already suffer from kidney stones or gout should you take extra care not to consume too much. It´s no more dangerous than many foods we do eat commonly, such as spinach, chard, parsley, tea, coffee, cocoa, nuts, rhubarb and black pepper. They all contain oxalic acid too. On the plus side, it is a good and tasty leafy herb, excellent sprinkled through a salad or made into rich soups – when you can really get to grips with handfuls of the weed! Cooking the plants, incidentally, renders them totally harmless - an amazingly good forage plant. Try it too as a stuffing for fish – it´s good, honestly! And oxalis roots roasted have a sweet nutty flavor popular as a vegetable and added to stir fries in New Zealand
And can you imagine your dinner guests faces when you serve up a green salad decorated with the fresh leaves and acidic yellow flowers of the scrumptious Bermuda Buttercup!
Warning: as always, when foraging for plants do be very sure that you know their provenance – they could have been sprayed. Safer to harvest your own plants.
We are closed on 1st and 6th January 2015.
Lorraine Cavanagh owns the specialist garden centre Viveros Florena, Competa, Malaga (garden centre, designers & landscapers) and is author of the best-selling Mediterranean Garden Plants and Citrus, The Zest of Life.
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