Gardening

Controlling Yellow Woodsorrel

Common woodsorrel, leaves and yellow flowers.

Common yellow woodsorrel can be a difficult weed to control, but this article will help you succeed! Photo: depositphotos

By Larry Hodgson

Question: Is there a way to stop weedy oxalis from invading my gardens?

Paul Gauvreau,
Quebec

Answer: There are over 500 species of Oxalis, but I’m going to presume you mean common yellow woodsorrel (Oxalis stricta), the most common weedy species in your area.

Common yellow woodsorrel is known under many other names: yellow oxalis, upright yellow-sorrel, lemon clover, sourgrass, sheep weed, pickle weed, etc. And there are other yellow-flowered Oxalis it closely resembles, including creeping woodsorrel (O. corniculata) and slender yellow woodsorrel (O. dillenii). They share many of the same common names and have a similar habit. And need the same type of treatment as well.

Common yellow woodsorrel with red leaves.
Sometimes the leaves of common yellow woodsorrel are reddish. Photo: depositphotos

Common yellow woodsorrel (O. stricta) is a small weedy plant with a stem that is upright at first (the sense of stricta), but then becomes creeping. Its small leaves are made up of three heart-shaped leaflets that close at night. The leaves are usually green, but can also be reddish.

This three-leaflet arrangement leads many gardeners to assume woodsorrel is a clover, but the two are not related. Indeed, the wide-open, 5-petaled, yellow flowers of the woodsorrel, borne throughout the summer, look nothing like the globular clusters of narrow flowers that make up clover blooms.  

This short-lived perennial or annual spreads by seed (the seed capsule explodes when touched, launching seeds up to 16 feet/4 m from the mother plant). However, it also proliferates abundantly by underground rhizomes. It grows in the sun or shade in almost any soil.

This species of woodsorrel is native to North America and parts of Asia, but is also well established as a weed in Europe and elsewhere.

Don’t Yank, Cut!

When it comes to trying to keep this plant under control, that can be a bit difficult.

First of all, never try to pull this plant out or hoe it into submission. That only breaks its rhizomes into pieces, each of which produces a new plant. The more you try pulling or cultivating it, the worse the problem becomes!

Instead, try a two-step technique. First, cover the area with at least 3 inches (7 cm) of the mulch of your choice. This will prevent the seeds of future generations from germinating. That’s because the seeds fall through the cracks in the mulch, ending in darkness on the soil underneath, but can’t germinate unless they are exposed to sunlight. Plus, the mulch will help snuff out some of the smaller, weaker offsets that inevitably try to push up through it. 

However, some baby plants will be strong enough to make it through the mulch. That’s where step 2 comes in. Whenever you see a stem of woodsorrel emerging from the mulch, cut it off at the base. If you always cut the stems off promptly, the plant won’t be able to carry out photosynthesis and will eventually starve to death. And in addition, cutting it back will prevent flowering and therefore fresh seed production.

You can be sure, however, that the plant will resprout more than once before giving up the ghost, so you have to keep at it: it’s a very stubborn weed!

Eat the Thinnings!

Green capsule of common yellow woodsorrel.
The green seed capsules are particularly delicious! Photo: depositphotos

And while you’re cutting the plant back, have a feast! Its leaves, flowers and seed capsules are edible with a very pleasant tart, lemony flavor, much like sorrel (Rumex acetosa). (That’s where the name woodsorrel comes from since, except for taste, sorrel and woodsorrel look nothing alike!) The thinnings are usually eaten raw, either straight from the plant or in salads, but can also be cooked. Very rich in vitamin C, this plant was once used to treat scurvy, among other medicinal uses.

Obviously, several of its common names, including lemon clover, sourgrass and pickle weed, come from its refreshingly tart taste.

However, don’t eat too much woodsorrel (no more than one cup a day for an adult), as the oxalic acid it contains can inhibit calcium absorption. People prone to gout and kidney stones should avoid it entirely.

Woodsorrel: the weed you can control by eating!

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

11 comments on “Controlling Yellow Woodsorrel

  1. That what I did to stop it in my garden, I used coffee chaff & no more sorrel or any annual weeds.

  2. marianwhit

    Spot-on. This one came to me in nursery pots…never had it…according to Vascan this is introduced in most Canadian provinces. Ugh. I was afraid you would overlook “oxal”-ates. Foragers should be aware of which plants contain higher amounts of them too, as a “stacking” effect could cause problems. For those unaware, simply google “plants high in oxalates” and consume in sensible moderation.

    • Vascan is apparently wrong about this one. It was once thought it have been introduced to North America, but the consensus now is that it is a North American native that was introduced to Europe.

      • marianwhit

        Thank you…I have found other examples of VASCAN not being the best authority. Do you have a reference? I would appreciate having it.

      • When I check out a plant for whatever reason, I first start with Wikipedia. (I had to here at any rate, given the similar species.) I was actually surprised to discover they considered it North American and Asian, as this plant is often called oxalide d’Europe in Quebec. But then I went to http://www.plantsoftheworldonline.org, from Kew Gardens, the site I usually go to check current botanical names, and they give a long list of countries it is native to and introduced to.

      • marianwhit

        That is a great site…the science is in rather a state of flux with the interest in gardening for local co-evolved plant species, so it is interesting to see where the ideas originated and why. No end of entertaining study…and hair pulling as one scientific name after another gets changed, and what was “ok” to plant 20 years ago is not today. A bit like trying to change the tires on a moving car. Thank you, I appreciate your time and responses as always. 🙂

  3. I have a lovely cultivar called Volcano that returns every year from seed. It seeds everywhere but haven’t found it too difficult to keep under control in my very dry climate. Will try snacking on the leaves next year though. Good tip.

  4. In my sandy soil the green variety I have is easy to pull up when seedlings are small (and haven’t developed rhizomes). I also weed diligently, so it’s pretty much under control.

    I grow the dark red/purple one on purpose (came from a friend of a friend from Manitoba). It stays mostly where I want it (sidewalk cracks; edges of borders) and it adds nice splashes of red and yellow colour (so much so that others have asked me for some). Towards the end of summer and/or when it starts to look ratty with the heat, I yank it all out (again, it’s in first year, so no real rhizomes) and the next year it has seeded itself fairly gently but I pull out the ones I don’t want as they come up throughout the summer – the colour makes them easy to spot.

    In my elderly mother’s vegetable bed the green one spreads quite a bit, so I use a weed torch on it (and all the other weeds) in the spring and again in the fall. She has a small older patch elsewhere in the garden that I found difficult to pull up (forgot about the rhizomes!), so I planted some Geranium cantagabriese ‘Biokovo’, a great spreading shallow-rooted plant that is easy to pull up if it spreads too far. Hoping the geranium will help to control the sorrel.

    My spouse loves the thought of weeds you can eat and has been wanting to do that for a couple of years now. Will make a better effort at adding small amounts to our diet next year by snipping some of my red ones off.

  5. I have this all over my garden and imbedded in my “lawn”. I love it! I let it spread pretty much wherever it wants to. The only places I pull it out are in potted plants due to competition and around some vegetables. The bees absolutely love the flowers and I have no qualms with supplying them with the extra food. Plus, my “lawn” looks lovely with the little yellow blooms scattered throughout. I use the quotation marks because my “lawn” is just weeds that occasionally get mowed!

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