Another neighborhood walk introduced me to a weed I really had never noticed before. Upon first glance I was confused by the strange whorled leaves, which almost reminded me of a massive pearlwort. It was growing on a hell strip in bark mulch in an area almost completely devoid of other plants, implying regular herbicide use or plastic landscape fabric. Not a hospitable environment by any means.
As it turns out I wasn’t too far off the mark. This adaptable mystery flower is an odd little plant called corn spurrey, Spergula arvensis. It is in the Caryophyllaceae, a family that not only includes the pearlworts (Sagina) but also the campions, chickweeds, and carnations. If you look closely at the photo above you can even see the small flower buds, which will open into small whitish flowers.
Corn spurrey is not native to Oregon or the Americas in general. Most spurreys are found in Europe, northern Africa, and southwestern Asia and were introduced to the Americas. Corn spurrey has a history of use as a forage, as it can thrive in otherwise inhospitable environments that other forage plants struggle in. The utility of corn spurrey combined with a large amount of seeds produced per plant is why it was introduced, both intentionally and accidentally, many times outside of its native range.
Depending on climate and soil type corn spurrey can be a winter or summer weed. It can remain low to the ground, like in the picture above, or grow up to 20 inches tall in favorable conditions. In the norther hemisphere it tends to flower between February and October and the many seeds (between 2000 and 7000) it produces during this long period of flowering can last for years in the soil, popping back up years after seemingly successful control methods are taken.
The control methods that successfully control spurrey are few and far between. Mechanical removal is effective but labor-intensive, and generally does not work well if the plants are allowed to set seed. Mechanical methods can also disturb the soil, leading to more germination. Corn spurrey populations have also rapidly become very resistant to many common herbicides. Cultural controls can work as well: the plant seems to prefer more acidic soils, so liming the soil can help lessen infestation pressure by creating an environment the weed does not like. Animals also like it and will graze on it, though it reportedly is somewhat high in oxalate so may not work well for all kinds of livestock.
Corn spurrey has its benefits: it thrives in dry and inhospitable places, where it can provide green forage for livestock. It is tenacious and does well in human-damaged ecosystems. It is this combination of qualities that makes it a rather difficult weed, however, and of the various species of spurrey that have been introduced to North America it is corn spurrey that has the most weedy potential in agriculture and disturbed areas. Because the seeds generally need the soil to be disturbed to germinate in any significant quantity, however, they are unlikely to invade intact ecosystems where soil disturbance is far less frequent.
So if you see spurrey in your yard, do you remove it?
Probably, but if your main goal is native plant restoration rather than farming it is relatively low priority. Spurrey doesn’t have a long record of displacing native plants and are a lot better at colonizing regularly disturbed farm fields than forests and prairie. In environments with lots of disturbance, however, I could see spurrey gaining a foothold which is why I think it is safest to remove it. Also, try not to let it go to seed or you will need to deal with it for years and years.