At this time of the year the weeds are growing very well. Between the warm weather, moist soil and a small vegetable and flower canopy, the weeds have perfect conditions in which to grow.
The one weed that I see the most in the garden is yellow woodsorrel (Oxalis stricta). The light green to reddish-green clover-like leaves and bright yellow flowers announce that woodsorrel has taken over parts of the garden.
While yellow woodsorrel can be a perennial in fields or turf, in the tilled garden it usually grows as a summer annual. The plants can range in height from a couple of inches to almost two feet depending on the conditions. Most of the woodsorrel I see is on the short side. This plant prefers moist, fertile soil so it’s right at home in the vegetable garden.
While this variety of Oxalis looks a lot like clover and black medic, the one thing that distinguishes it from these plants is its leaves. They consist of three leaflets, each of which is clearly heart-shaped.
Yellow woodsorrel can spread by rhizomes (underground stems) but its primary means of spreading is through its seeds. The plant bears small yellow flowers with 5 petals in the spring and early summer with intermittent blossoming during the rest of the growing season. When the flowers are fertilized, an elongated, upright seed capsule forms. When it’s mature, the seed capsule explosively breaks open and ejects the seeds up to 12′ away from the plant. No matter how diligent you are at weeding, it’s hard not to miss a few of these plants. And when you let some grow and their seed capsules mature, seeds are spread all over the garden. Because of this it’s no surprise that yellow woodsorrel can be a ubiquitous weed in the garden.
Woodsorrel can be a difficult to pull because of its rhizomes and it responds to most broadleaf herbicides. However, the main way to control this weed in the garden is through cultivation. The good news is that it’s not a very aggressive or competitive weed so it won’t crowd out other plants. But given the way that it spreads its seeds, every seed capsule that’s allowed to mature means that there’ll be more yellow woodsorrel growing next year.
I was a little surprised to see that an Illinois wild flower site lists yellow woodsorrel as a wild flower. I guess it just goes to show that one person’s wild flower is another’s weed. While I can appreciate the flowers of this plant, it’s a weed to me and one that I encounter every year.