The Weekly Weeder: Whacking Weeds Can Work

          Whacking annual weeds can kill them, if you whack them low enough—right into the dirt, below the crown.  They have no means to grow without a crown, from which all their growth comes.  (Chickweed is an exception, as it does not have a crown and will keep trying to grow and set seed until it has made enough of it.)

          I saw weed whacking work several years ago, when the city or one of its maintenance contractors eliminated goat heads from the Wastewater Treatment Plant property for several years by repeatedly scalping the dirt where they grew with a string trimmer.  This year, they are blooming and seeding in their old locations near the back fence; apparently the maintenance contract has changed and the city’s institutional memory is short, but goat head seeds can sprout for at least 5 years and will come up all summer until frost.

          This year, I whacked the dense weeds along the irrigation ditch behind my mom’s house into the dirt in May, when they were still green and flowering, but hadn’t set seed yet.  A week later, I pulled a few that had been missed.  The next week, only the false dandelions had come back, and over two months later, that is still the case.

          Last week, I was pulling and cutting crab grass from the backyard below, and looking at the enormous quantity of spotted spurge growing along the same path, but not yet flowering, and asked myself why I didn’t just whack them all, as the annual weeds would be killed out, while the perennial grass and clover would come back from roots.  So I got my battery-powered trimmer out and started beating the dirt, working out which direction to work in order to throw the debris away from my legs and face.  The next week, that area was still quite barren.  This week, some were starting to grow back, and I whacked them again.

          I will have to repeat all summer and reseed clover in the fall, I am sure.  Spring weeds start in the fall and winter, flowering and setting seed around the same time in the spring, allowing one to kill them out for the season with one soil-scalping before they are ripe.  Some summer annuals, like star thistle, start together in spring and can be killed out as they start to bloom in early summer.  Most summer annuals keep sprouting through the hot weather, particularly where they are watered.  Goat heads have a final flush of sprouting as the weather cools in the fall, just as heron’s bill is starting its fall sprouting season.

What does not work to kill weeds, of any sort, is cutting two inches above the ground.  They continue to spread their flowers and ripen seed below the cutting height.  Weed control is seed control, and if the plants are still flowering, they are still violating our city code, which requires that one prevents flowering, seeding and noxious growth by cutting or killing.

                             

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com

The Weekly Weeder -- Mare’s tails are pretty, invasive

          Mare’s tails are starting to wave their pretty tall plumes along our roadsides and sometimes in gardens.  Years ago, I let them grow to see what they would do, was disappointed that they were not more showy, and started pulling them as I saw them.  As they came to dominate our roadsides, I realized that they spread on the wind as badly as any wild lettuce.

          They grow up to about 6 feet tall, and for a few years they dominated our roadsides in many places.  But they seem to have been replaced in most places by prickly lettuce, which is not an improvement. 

Small mare's tail starting to "bolt" (putting up its flower stalk)

          Weeds come and go depending on each particular year’s weather.  Weather in any one year tends to bring up particular plants; I call them “the weed of the season.”  For a few years, a plant may suddenly appear everywhere because of such good sprouting conditions for it; the same conditions don’t repeat themselves, and that plant slowly disappears. 

Mare's tail rosette--Joseph M. DiTomaso, UC-Davis, Bugwood.org

          Mare’s tail is also known as horseweed and has the Latin names Conyza Canadensis, or Erigeron Canadensis; they are the same plant.  It is an annual flowering weed that is easily killed with hand tools or hand pulling, not so easily with herbicides.  It starts with a rosette of lance-shaped leaves, some with coarse teeth that point outward from the center of the plant, some smooth-edged and slimmer.  It grows a hard stem as it bolts and flowers with little white composite flowers lacking petals that form a 2-6 foot tall, fluffy white plume, and makes fuzzy seeds that fly on the wind.

"Naked" horsetails popping up on a newly landscaped tree strip outside the landscape cloth

Its common name is easily confused with horsetails, also called mare’s tails, Equisetum species, which are a perennial fern that has round, jointed hollow stalks with round, thin, short branches in whorls up the stem, forming a bushy tail shape up to 2 feet tall.  Another variety of horsetail has only bare stalks without branching.  Both come up from a deep, rhizome root and take great patience and persistence to eliminate by pulling.  After 15 years of working my parents’ yard, I am only now starting to make real progress against it, as I only started consistently working their yard in the last 3 years.

Branched Equisetum, Wikipedia

          Mare’s tail, on the other hand, I have not had trouble eliminating from any property, so long as it is not growing nearby.  It pulls fairly easily from damp ground.  In dry ground, cutting it under the crown, or to the ground when blooming, will kill it.  In lawns, its hard stem keeps growing flowers and seed, just like prickly lettuce if one doesn’t cut it to the ground.  Its seeds do not seem to be persistent.

It was the first weed to develop glyphosate resistance, according to Wikipedia, from its use in no-till farming, and it is now resistant to several herbicides.  At least one farmer in our area was doing no-till for about 20 years, but stopped a few years ago when Josephine County was campaigning to pass a GMO growing ban, which has since been overturned.  Nonetheless, they will not resume using Roundup-ready corn and glyphosate to grow animal feed, as the news that they were growing it hurt their sweet corn sales.

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com