yellow wood sorrel (ptoe-oxalic acid)
Yellow wood sorrel (Oxalis stricta) is another backyard edible. The leaves, flowers and unripe fruits are edible, with a sour, tart, lemony flavor; it’s sometimes referred to as “sour grass” because of the sour taste. Wood sorrel can be added to salads, soups, or sauces, or used as a seasoning. The leaves can be steeped in boiling water for 5-10 minutes and then sweetened to make a refreshing drink similar to lemonade. I am always reading that it should be consumed in moderation because the plant contains oxalic acid which is toxic in excessive amounts, but looking at this chart you get more oxalic acid from parsley, purslane, chives, rhubarb stems and spinach.
| Vegetable or Fruit |
Oxalic Acid Content as a percentage |
||
|---|---|---|---|
| USDA | Dr. Duke | Litholink | |
| Amaranth | 1.09 | — | — |
| Apples | — | — | 0.00 |
| Apricots | — | — | 0.00 |
| Asparagus | 0.13 | — | 0.01 |
| Beans | 0.36 | 0.03 | 0.02 |
| Beans, Fava | — | 0.01 | — |
| Beans, Garbanzo | — | 0.00 | — |
| Beans, Soy | — | 0.08 | — |
| Beets | — | 0.04 | 0.68 |
| Beet Greens | 0.61 | — | — |
| Blackberries | — | — | 0.02 |
| Blueberries | — | — | 0.02 |
| Broccoli | 0.19 | — | 0.00 |
| Brussels Sprouts | 0.36 | — | 0.00 |
| Cabbage | 0.10 | 0.04 | 0.00 |
| Carrots | 0.50 | 0.01 | 0.00 |
| Cauliflower | 0.15 | 0.01 | 0.00 |
| Celery | 0.19 | — | 0.02 |
| Chicory | 0.21 | — | — |
| Chard, Swiss | — | — | 0.65 |
| Cherries | — | — | 0.00 |
| Chives | 1.48 | — | 0.00 |
| Collards | 0.45 | — | 0.07 |
| Coriander | 0.01 | — | — |
| Corn, Sweet | 0.01 | 0.01 | 0.01 |
| Cucumbers | 0.02 | — | 0.00 |
| Currants, Black | — | — | 0.00 |
| Currants, Red | — | — | 0.02 |
| Dandelion Greens | — | — | 0.02 |
| Dewberries | — | — | 0.01 |
| Eggplant | 0.19 | 0.03 | 0.02 |
| Endive | 0.11 | — | — |
| Escarole | — | — | 0.03 |
| Garlic | 0.36 | — | — |
| Gooseberries, Green | — | — | 0.09 |
| Kale | 0.02 | — | 0.01 |
| Lambsquarters | — | 30.00 | — |
| Leeks | — | — | 0.09 |
| Lentils | — | 0.02 | — |
| Lettuce | 0.33 | 0.01 | 0.00 |
| Melons | — | — | 0.00 |
| Mushrooms | — | — | 0.00 |
| Mustard Greens | — | 0.13 | 0.01 |
| Nectarines | — | — | 0.00 |
| Okra | 0.05 | 0.01 | 0.15 |
| Onion | 0.05 | 0.00 | 0.00 |
| Parsley | 1.70 | — | 0.10 |
| Parsnips | 0.04 | 0.02 | 0.01 |
| Peas | 0.05 | 0.01 | 0.00 |
| Peaches | — | 0.00 | 0.01 |
| Pears | — | — | 0.00 |
| Peppers, Sweet | 0.04 | 0.12 | 0.02 |
| Pokeweed | — | — | 0.48 |
| Potatos | 0.05 | 0.02 | 0.00 |
| Pumpkin | — | 0.04 | — |
| Purslane | 1.31 | 1.68 | — |
| Radishes | 0.48 | 0.01 | 0.00 |
| Raspberries, Black | — | — | 0.05 |
| Raspberries, Red | — | — | 0.02 |
| Rhubarb (stems) | — | 1.34 | 0.86 |
| Rutabagas | 0.03 | — | 0.02 |
| Shallots | — | 0.00 | — |
| Sorrel | — | 0.30 | — |
| Spearmint | — | 0.00 | — |
| Spinach | 0.97 | 0.66 | 0.68 |
| Squash | 0.02 | — | 0.02 |
| Strawberries | — | — | 0.01 |
| Sweet Potatos | 0.24 | 0.10 | 0.06 |
| Tomatillos | — | 0.05 | — |
| Tomato | 0.05 | 0.03 | 0.00 |
| Turnips | 0.21 | — | 0.00 |
| Turnip Greens | 0.05 | — | — |
| Watercress | 0.31 | — | 0.01 |
High oxalic acid foods should be avoided by those with kidney disease, kidney stones, rheumatoid arthritis, or gout. To read more about oxalic acid in foods and get a better understanding of this chart visit growingtaste.com.
Wood sorrel is another great plant to link to the periodic table, the formula for oxalic acid is H2C2O4.
Oxalis means ”sharp” in Greek and Sorrel means “acidic” or “sour” in French.
Although wood sorrel has three-lobed leaves, it is not related to the clover which is in the Trifolium family. Those heart shaped leaves belong to the Oxalis family not the clover family.
Here is a photo of white clover leaves, they are more oval shaped.
Shooh, I hope that wasn’t too much info on the science of wood sorrel and oxalic acid; sometimes I just can’t stop myself. 
Great post, Lisa! Goose and Binky eat sorrel(not wood) raw all summer long. I, too, have read the warnings. I just make sure they only eat 2 or 3 leaves a day and not every day. But they do love it!
I’m thinking about starting a weed garden in one of our co-op school’s garden boxes, so I love all your posts about edible wild plants.
I’m not sure I’m going to be able to convince anyone to *add* weeds to our garden though. 
Leave it to Lisa to teach me what I’ve been calling clover are actually wood sorrel. Good to know! We have lots!
I think it’s so funny that I know plants by look and sometimes a common name but don’t know what it really is and what it’s good for. Thanks for sharing the science too.
So all this time I’ve been searching for a 4 leafed cover, it’s been in a sorrel patch?! As kids we always sucked the stems of the little yellow flower for their sweet tangy taste.
Glad to have my clover misdiagnosis finally sorted out… no wonder I’ve never found a 4 leafed clover even though I’ve searched for hours and hours!
Blessings and magic.
We love to munch on wood sorrel. Susun Weed suggests eating foods high in calcium with your leaves that are high in oxalic acid, because it interferes with calcium absorbtion.
I have suffered from kidney stones for years and had no idea there was a link to oxalic acid. Thanks for this information
I just added a link to this post in the wild edibles post I did earlier this summer.
http://fimby.tougas.net/weeds-you-can-eat
Love all you write about over here Lisa (smile).
No! Not too much information. I’ve actually wondered about this myself and now you’ve answered it for me. My kids love eating this stuff raw all summer from the yard and garden.
Oxalic acid! So that’s why my kidney doctor told me to stop eating my favorite spinach salad. Yes, I get kindey stones, four times so far. When he started listing things I couldn’t have I said, “Just tell me what I CAN have.” Thanks for making it so easy to understand. You’re a true gem. xxoo
This was a great blog post, thank you so much
Oh no! My girls have been eating tons of chives from the garden all summer long! (but they seem to be okay so I guess I won’t worry too much.) Very much enjoying your edible wild foods posts. But why is lambsquarters highlighted bright red?? I see it has a high number, but I’m not sure what your columns mean… and lambsquarters is one of my favorites…
Thank you for that great information
Lady, you can go on about wood sorrel all you’d like – we’ll listen! Eliza loves sorrel and looks for it everywhere – I’ll often hear her telling someone (like my dad!) the difference between clover and sorrel.
thank you for this. i have loads of it in my back garden. i thought it was clover.