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Ann Wright: Weeds — The good, the bad and the ugly

Ann Wright
Columnist

Summer gardening is not without challenges, including the emergence of plants we don’t want growing along with our prized vegetables. But, a weed to one gardener may be considered a virtuous plant to another. Ralph Waldo Emerson said, “A weed is a plant whose virtues have not yet been discovered.” Regardless of how each person defines a weed, there are some that are more problematic in the landscape than others.

Drilling further into the definitions and characteristics of weeds, the California Invasive Plant Council (Cal-IPC) categorizes weeds into noxious and invasive categories. Noxious weeds — often invasive, are those that are likely to spread causing significant economic, environmental or human harm. Each plant is characterized based on an assessment of the ecological impacts of the plant.

Generally difficult to control, invasive plants damage ecosystems by crowding out native species, reducing the value of habitat for wildlife. One such weedy undesirable is yellow star thistle (Centaurea solstitialis) which was introduced to California around 1850. This thorny pest infests between 10 and 15 million acres in California and can be commonly seen in open rangeland areas, on roadsides, pastures and hayfields. A rapid colonizer, this plant forms dense infestations that compete with desired species for water. Studies indicate that yellow starthistle significantly depletes soil moisture in foothill and grassland ecosystems. Billions of gallons of water are consumed by this invasive plant, impacting the economic and ecologic well-being of the surrounding area. Control of star thistle may not happen in a single year, but a management plan can be developed using cultural, biological and/or chemical means. The UCANR’s IPM website (www.ipm.ucanr.edu) offers a pest note with more information on how to manage this and other weedy undesirables.

Not to be confused with the pretty purple annual “morning glory” (Ipoema), field bindweed (Convolvulus arvensis) is a tough perennial found below 5,000 feet elevation. (The flowers of the annual morning glory are larger and showier than the pinkish-white blossoms of the bindweed.) This persistent weed emerged in my garden last year.

To learn more about weeds, you are invited to view the Nevada County Master Gardener’s online workshop, “Weeds: The Good, The Bad, The Ugly, which was recorded at our “live” zoom presentation last Saturday.

Spreading extensively from rootstock and seed, the roots and rhizomes of bindweed can produce buds of new shoots; roots are capable of growing to 14 or 15 feet deep. An average plant produces about 550 seeds. Vertical root fragments as small as two inches can grow into a new plant; lateral roots can turn down and grow into a new parent plant with an equally deep root system. Field bindweed grows along the ground unless it has a plant or structure to climb. It is often found twining around upright plants such as corn or grapevines. Bindweed is a nasty invader and wouldn’t you know? It’s drought tolerant, loves clay soil and seems to thrive in hot temperatures.

But my efforts at controlling it in my garden have helped: a winter of solarizing the space with large sheet of black plastic, in addition to spring and early summer soil cultivation with a vigorous program of weed-pulling, have helped decrease the number of plants.

Currently a number of fields and roadsides are a blaze with yellow. Many of these yellow flowers look like common dandelions (Taraxacum officinale), but may be the smaller common catsear (Hypochaeris radicata). Known also as false dandelion, hairy cat’s-ear, or flatweed, common catsear blooms from May to November with small yellow flowers that are often mis-identified as dandelions. But unlike the dandelion, common catsear has branched flower stems and hairy leaves whereas dandelion leaves are hairless and have pointed lobes. The stems of dandelion do not branch and are often tinged with red. Both develop puffy seed-heads.

There are many varieties of weeds in our foothill areas, and identifying the weeds plaguing your yard is the first step in managing them. To start, look up the weed on the UCD IPM website (http://ipm.ucanr.edu ) to help find out what the weedy pest is. Management strategies are located in the information. The course of management may take some time – especially for some of the cultural methods.

To learn more about weeds, you are invited to view the Nevada County Master Gardener’s online workshop, “Weeds: The Good, The Bad, The Ugly, which was recorded at our “live” zoom presentation last Saturday. To access the recorded program, go to our website at http://ncmg.ucanr.org/ and look for the links on our home page. Watch for more free live Zoom workshops in the future.

It is our hope that we will be able to meet in person one day soon. For now, the Master Gardeners of Nevada County are accessible via our website – ask questions via the “Got Questions” link at the left side menu. Live radio shows are being broadcast on KNCO radio, 830am dial from 10am to noon each Saturday. Thank you to our community for your patience and continued support during these different times.

Ann Wright is a Nevada County Master Gardener.


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