Thanks to the bouts of rain after Thanksgiving, all the slumbering little green creatures in the park are perking up, pushing up through the soil, and dressing the park’s brown slopes in a verdant robe. It won’t be long before we see signs of spring.
But before that, we’re seeing signs of weeds. Park landscape management sent mowers over the dry brown pastures late last summer, while the dozens of Bristly Oxtongue plants were already in seed. The whirling blades leveled the weeds but also scattered their seeds over a wider area. Result: this year we have not only dozens but hundreds of Bristly Oxtongue weeds punctuating the lawn.
This weed, native to the Mediterranean but thriving in coastal California, will grow up to 3 1/2 feet high. It starts in winter, early, and stays active until late in the summer. Depending on conditions, it operates either as an annual, a biennial, or a perennial. It is very hard to get rid of.
Weed control sources like the UC Davis Weed Book recommend hand pulling or hoeing in wet soil, being sure to remove the roots down to two inches. Repeated mowing before the plant sets seed reduces plant size but doesn’t prevent regrowth. There are no biological control agents. Control measures such as fires and herbicide chemicals cannot be used in the park.
The Invasive Species Compendium, an encyclopedia of weeds, cites research showing that in coastal areas, “only solarisation methodology achieved a reduction in the existing invasive weed species and stopped a new invasion.” Soil solarization involves irrigating the soil heavily and then covering it tightly with plastic sheets. Under sun exposure, the soil under the plastic heats up to the point where seeds on and under the surface are killed. Details on the technique here.
Neither hand pulling nor solarization are likely to happen in the park anytime soon. Expect repeated mowing, even late in summer. In a few years, we’ll have a lawn of Bristly Oxtongue with little patches of grass inbetween.
Bristly Oxtongue isn’t all bad. There’s even a poem about it. The Brits seem rather charmed by the plant; see Natural Lizard, the Natural Medicinal Herbs website, the Bug Woman of London, and Jeremy Bartlett’s Let it Grow blog. Apparently the young leaves can be eaten, if boiled first; and the stems are said to be edible, if peeled first. But bitter.