Yellow Oxalis Weed by the Millions

A weed that I’ve enjoyed seeing, until they had a population explosion in the vegetable garden recently, is the yellow oxalis or sour grass.

Yellow oxalis is also known as Yellow Wood Sorrel, which is the common name used for two closely related plants, Oxalis stricta and O. europaea. Both plants are native to the eastern United States. The outward difference between the two species is in the way the seed pods are held. The seed pods of O. stricta have a sharp angle in their stems, while those of O. europaea are not bent. Photos in this post are of O. stricta.

The leaves are like shamrocks, so sometimes we call it that. Each leaf is made up of three heart-shaped leaflets, joined at their bases.

By June the earliest flowering oxalis will set seed. Seeds develop in their candle-like spikes, which are the pieces to eat for a sour treat, although the foliage tastes sour too.

Yellow oxalis, Oxalis stricta, plant developing its candle-shaped seed pods.
Yellow oxalis plant developing its candle-shaped seed pods. Photo taken 9 June 2011.
Close up view of sour grass, Oxalis stricta, seed pods.
Close up view of sour grass seed pods. Photo taken 9 June 2011.

While pulling out weeds we often uncover toads. The little ones we find in the springtime are actually cute!

A garden visitor we like to see - they eats lots of insects - American Toad, Bufo americanus.
A garden visitor we like to see - they eats lots of insects - American Toad, Bufo americanus. Photo taken 9 May 2011.

What Are These Tiny Blue Flowers In The Yard?

Flowering plants number in the thousands or hundreds of thousands actually. Indeed, the huge variety of types of flowers is one thing that draws me to them…the seemingly infinite arrangement of colors, shapes and sizes.

Sometimes I find a flower that is more of a curiosity than anything else. Take for instance these tiny little flowers that come out in early spring. You can find them appearing in flower beds and walkways, along roads and in lawns.

To find out what these little plants are, you’d need a weed book, I guess. The flowers are so tiny as to disappear from view in a short distance. With blossoms that are 1-2 mm across, these posies won’t appear in a wildflower book for their flashyness. Not exactly eye-catching, unless you’re on the ground with them.

Those that we see in the lawn near the garden have a tiny blue flower with four petals. In the center of the blossom is a white ring that surrounds a couple of light-colored stamens. The flower looks like it belongs to the Speedwell group.

The plant has a sprawling habit as it sends out hairy, maroon runners in all directions. The broad, spade-shaped leaves along the runners are scalloped on the edges and lie opposite one another. Where the runners terminate, the leaves become less broad and they’re more tightly packed together. Flowers appear singly in the leaf axils. Photos taken 3 May 2011.

Tiny blue flowers appear at the end of maroon-colored runners.
Tiny blue flowers appear at the end of maroon-colored runners.
Tiny blue flowers magnified 3X.
Tiny blue flowers magnified 3X.

Right next to the tiny blue flowers were a bunch of tiny white flowers. These little curiosities appear in the lawn each spring.

The tiny white flowers seem to be a form of speedwell also, with opposite leaves that are jagged or notched. The leaves are similar to those of the tiny blue flower, except drawn out or stretched into thinner, oval shapes. The white flowers have fours petals and occur at the leaf nodes, not terminally. Overall, the tiny white flower plant is taller and has more vertically rising stems than the tiny blue flower plant.

Stems grow vertically in the tiny white flower plant.
Stems grow vertically in the tiny white flower plant.
Notched, oval-shaped leaves are stemless on this yard weed.
Notched, oval-shaped leaves are stemless on this yard weed.

So, it’s just a curiosity I have about these little plants. I suppose that ants or flies would pollinate the tiny flowers. Plenty of them get pulled out of flower beds or mowed down by the lawnmower, but sometimes they come back.

It turns out that the tiny blue flowered plant is called Corn Speedwell, Veronica arvensis. I came across its picture when looking up Blue-Eyed Grass in the Audubon Field Guide to Wildflowers. Corn speedwell is not native to America, nor does it appear to have edible or medicinal qualities.