This is a post from my old PhD blog. It was first posted on 5/26/15
I was weeding in my back patio area with kiddo this week when I found a flower I remember fondly from my childhood. We always called them lemon flowers, they were everywhere around the pond at our apartment when I was a kid. Giddy that I had found them, I called Boo over and showed him the little yellow flowers. My mom had always called them lemons flowers, why did he think they were called that? Obvious answer, because they are yellow. Good guess! But then I told him to eat the little yellow flower, to which I received a rather skeptical look. I assured him it was ok and so he popped the petals into his mouth. “It’s sour like a lemon too! Can we let those grow? Don’t weed them!” So I left them alone as I both enjoy the way they look and taste.
The botanist in me wondered what was the proper name of these little yellow flowers, surrounded by what looked like clover leaves. It took a some searching but I discovered these flowers are Oxalis stricta L. commonly called yellow oxalis, yellow woodsorrel or lemon clover (so my Mom was close on her common name). They are edible and very refreshing! In fact, they are not a bad source of vitamin C. In 100 grams of yellow oxalis there is 59 milligrams of Vitamin C. In comparison, 100 grams of clementine oranges has 48.5 milligrams. That’s a little over 17% more Vit C in these common field flowers. The sour, tangy, lemon-like flavor is caused by the Vitamin C and Oxalic acid content. While I love munching on them when out and about, be aware that, as with many things, a large amount of oxalic acid can be toxic and you should not eat these if you have a kidney disorder. The leaves and flowers can add a nice zing to your salad, the leaves and stems can be juiced to get an acidic juice (like vinegar), and the whole plant can be boiled and used as orange dye.
Now one should not go out and eat any shamrock-esque leaves or yellow flowers that they encounter. How do you know that you have found a grove of yellow oxalis? Here are a few things you can use to identify it. The leaves are composed of 3 heart-shaped leaflets, which fold up at night or during abiotic stress, such as heat. The yellow flowers have 5 petals, 5 sepals (the green part of the flower), 10 stamens (produce pollen/sperm) and a single pistil (contains ovary). It will produce flowers all spring/summer long. A long root connects many different vegetative clumps, which is one of the reasons this plant does so well in the cracks of sidewalks. The root can spread along the crack and send up lots of sprouts. The seed pods have 5 ridges and a pointed top.
According to the USDA Plants database, yellow oxalis is native to 44 of the lower 48 states of the United States and invasive in all but 1 southern Canadian province. So if you are in the US/S Canada and not in Alberta, Oregon, California, Nevada or Utah, you should be able to find some yellow oxalis around. They like most growing conditions and spread rapidly, which has led to them often being considered a weed in ornamental planting areas (lawns/gardens). Next time you come across them, instead of just weeding them away, give the flowers a little taste (those are my favorite part!). If you do want to eliminate them, but sure you get the entire root system, otherwise the root remaining will just send up another shoot. Personally, I’m cultivating a little garden in the corner of our yard which I’m hoping will be full of yummy flowers for us all summer long.