Tuesday, May 26, 2015

Yellow Oxalis

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.

Personal image from the backyard
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. 
"6h common yellow oxalis" by 6th Happiness - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons
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.


Saturday, May 16, 2015

Running Buffalo Clover

According to the Internet, yesterday was Endangered Species Day! I saw a lot of posts about all of the endangered animals worldwide, of which there are a lot of fascinating and adorable creatures. But, I noticed very little attention being paid to the plant kingdom. I felt someone should change this! According to the US Fish & Wildlife Service’s Environmental Conservation Online System, there are over 600 federally recognized endangered plant species in the United States. If you count threatened and endangered, there are a total of 886. Being from the Midwest, I decided to pick a plant that was endangered in my local area to highlight today. Without further delay, may I introduce Trifolium stoloniferum Muhl. ex Eaton, commonly called running buffalo clover. 
Photo by U.S. Fish and Wildlife Service, Sarena Selbo

Running buffalo clover is part of the Fabaceae family, the legumes, which also includes soybean and peas. It used to be wide spread across the Midwest, commonly reported in the trails left by buffalo (hence the common name), deer and elk. At one point, it was considered to be extinct until two populations were discovered in West Virginia in 1985. Since then populations have been rediscovered in Indiana, Ohio, Kentucky, Missouri and Arkansas. 

I’m sure you’ve seen clovers, I know I spent plenty of time as a child combing through a field of clover looking for the supposedly lucky 4 leaf variety. There are over 200 recognized species of clovers, so how does one identify the endangered running buffalo from the more common introduced white clover (Trifolium repens L.)? First, buffalo running clover puts out runners over the soil letting it spread across the plains, hence the running portion of its name. Second, notice in the diagram drawings that the stem of white clovers flower do not have any leaves, while the running buffalo has two paired triple leaves on the flower stem. Third, buffalo running clover lacks the white lines on its leaves that are typically observed in clovers of the genus Trifolium. And last, if you can get up close to the flowers, they have little purple tinges where white clover are all white.
Running Buffalo Clover
White Clover

When I first saw that a clover was endangered in my area, my immediate thought was that it must have been out-competed by any number of the clovers that have been introduced. Native species being squeezed out by introduced species is common in the plant kingdom. But after some reading, it turns out that running buffalo clover was decimated by the loss of bison and other large herbivores from the Midwest. The clover needs the disturbance of herbivory to thrive. The seeds can be spread via passage through the intestinal system. So it would appear that the loss of the major herbivores has led to the decline of this unique clover species. Though development (loss of habitat) and competition with invasive species certainly do not help its recovery chances. 

One of unique things about running buffalo clover is it's lack of nodulation. A lot of legumes have nodules where symbiotic Rhizobium bacteria reside and fix nitrogen. In a field study, there found no nodules on the roots of running buffalo clover and no significant nitrogen fixation rates. In comparison, white clover fixes a large amount of nitrogen (128 kg N/hectare/year) because of nodules containing Rhizobium. Was the lack of symbiosis always the case for running buffalo clover or has it's particular species of bacteria been lost to time? The answer to that question is unknown. 

Hopefully the next time you're on the hunt for a four leaf clover, you will now recognize running buffalo clover by using the tips above. They should be flowering right about now!

Diagrams from USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 2: 357-358