Posts Tagged: Oxalis
How Cold Is It? Ask Siri and Check for Bees
Have you ever asked Siri "How cold is it?" Siri, a computer program known as Apple's "intelligent...
A honey bee foraging on oxalis at noon on Wednesday, Jan. 25 in Vacaville, Calif. Temperature: 53 degrees. (Photo by Kathy Keatley Garvey)
Pollen-packing honey bee on oxalis. (Photo by Kathy Keatley Garvey)
There she is! Silvery wings and all. (Photo by Kathy Keatley Garvey)
Dear Little Buttercup.... NOT!
Garden Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa
(minor correction October 31, 2016)
Client's Request: How can I get rid of oxalis in my yard? I pull it out and think I've got it all, but it just comes back with more gusto the following year. It's annoying, to say the least!
Homeowners and gardeners wishing to eradicate Bermuda buttercup face a tenacious, prolific weed which has devised many successful survival strategies. Each year, after the first seasonal rains, and sometimes before in a dry year, about a dozen ovoid bulbils develop along the length of the threadlike, underground rhizome. These readily detach from the rhizome to replenish the soil seed bank.
Another survival technique of Bermuda buttercup is that, after initial removal by hand, new plants will grow from broken off stem segments left in the soil. Several passes at hand weeding may be necessary to completely remove this new growth. Discouraging survival of Bermuda buttercup can usually be accomplished by gently pulling on the plant and removing all of it just as it is about to flower. By this time, the parent bulb energy reserves are exhausted. The parent bulb should be completely dried out and most young bulbils are too immature to survive disturbance.
Though prevention is the best control method, soil solarization can reduce the bulb population. To be effective, solarization using a clear plastic tarp treated with an ultraviolet light inhibitor must be in place for no less than 4 consecutive weeks during June, July, or August. The sun's rays will heat up the soil to temperatures that are lethal to Bermuda buttercup bulbs (and most everything else in the top several inches). Some researchers investigating approaches for controlling Bermuda buttercup also suggest covering it with stiff cardboard and applying a thick layer of mulch. The goal is to weaken the bulbs and deprive the plant of sunlight, causing an inability to photosynthesize and eventual death by starvation. Chemical control can affect the top growth but is ineffective in preventing bulb germination.
The lack of movement of water and air between compacted clay soil molecules promotes the survival of Bermuda buttercup bulbils. Adding nitrogenrich organic matter will loosen existing soil particles and benefit soil structure by increasing porosity and improving drainage.
While complete eradication is practically impossible to achieve, following strict noncontamination practices, mulching, solarizing, improving soil structure and drainage are all steps gardeners can take to create an environment unfavorable to the establishment and survival of Bermuda buttercup.
For further information on managing this pest, visit www.ipm.ucdavis.edu and download UC's free Pest Notes publication 7444 entitled “Creeping Woodsorrel and Bermuda Buttercup.” (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7444.html)
UC Master Gardener Program of Contra Costa's Help Desk (CG)
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This is an updated article authored by Chantal Guillemin, UC Master Gardener, and originally published in the March 19, 2011, Contra Costa Times. The HOrT COCO blog editor takes all responsibility for the above updated version.
A minor error was corrected Oct 31, 2016 to reflect, per the Pest Note above that woodsorrel can be a pest in nursery container-grown plants, while Bermuda buttercup isn't. See the Pest Note referenced abov for the specifics..
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Come to the UC MGCC Program's Great Tomato Plant Sale
Walnut Creek 4/2&9, Richmond 4/9, and Antioch 4/16
Click for locations and plant lists!
Dozens of heirloom tomatoes & vegetables chosen especially for Contra Costa
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/CCMGBlog/).
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Battling Several of Contra Costa County's
More Noxious Garden Weeds
Advice for the Home Gardener from the Contra Costa Master Gardeners' Help Desk
Client's Problem and Questions:
Advice from the CCMGs' Help Desk
"Researchers around the world are investigating approaches for controlling Bermuda buttercup. Some suggest covering infestations with stiff cardboard, then covering the cardboard with a thick layer of organic mulch to kill the plants and weaken the bulbs, making them less capable of competing with desirable plants. Keep the mulch on the infestation until the mulch and cardboard have rotted, then plant competitive ornamentals into the soil-mulch mixture."
The Contra Costa Master Gardener article, "Oxalis: From Ornament to Nuisance" will give you even further insight on controlling Oxalis per-caprae. http://ccmg.ucanr.edu/files/83817.pdf
I know that the management of these weeds is a big challenge and wish you all the best in dealing with it!
Contra Costa Master Gardeners' Help Desk
Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/
You can grow this fruit in Southern California, but can you sell it:?
What a gorgeous fruit. Slice it cross-wise and you have a star-shaped garnish for salad or cooked dish. But you need to find a buyer for it.
The star fruit, or carambola, is a member of the oxalis family. Only one other species is commonly cultivated for its fruit, the less esteemed, more frost sensitive Averrhoa bilimbi. The star fruit is native to Sri Lanka and popular throughout southeast Asia, India, southern China, New Zealand, and Australia. The tree is well adapted to a variety of tropical and subtropical climates and is now cultivated in Mexico, the Caribbean, Central and South America and to a lesser extent, Israel. The main restricting factor in California is frost, the tree being about as cold hardy as limes. The golden-yellow fruit is 3 to 8 inches long and 2 to 4 inches in width with an star shaped cross section. The thin skin, appears waxy but is edible. The sweet to acid flesh is juicy, crisp and mild flavored and usually eaten fresh. It makes an extremely attractive fresh or cooked garnish when cut to reveal its 5 or 6 pointed star cross section. It is also made into relishes and chutneys. The sourer varieties contain more oxalic acid and can be used for polishing brass and removing rust stains. The wood is used for furniture and construction. The fruit is used medicinally as a folk remedy for a large number of maladies including hangover.
star fruit
This (Wild) Onion Makes Me Cry!
When it recently rained for days in a row, I stood at the window and watched my weeds grow. I have quite the variety of weeds, as I suspect we all do, but some I don’t really mind. For example, Oxalis is extremely invasive, but it is somewhat pretty and is almost enjoyably easy to pull up from the soil. Even if I don’t always get all of the bulbs like I should, at least I can hold some hope that I’m weakening the bulbs by pulling up the rest of the plant. Plus, Oxalis goes dormant with the summer heat. Out of sight, out of mind, right?
But my least favorite? The wild onion, Allium triquetrum, which is also known as the three-cornered leek. It’s not an ugly weed—in fact, it is sometimes cultivated as an ornamental. It has flower stems of about 1 foot tall, with nodding clusters of small, bell-shaped, white flowers. Not surprisingly, it has a strong onion smell.
The wild onion multiplies quickly, spreading by bulbs and seeds, and it is very hard to remove once established. Like Oxalis, it can be controlled by digging up the entire plant, including the bulbs. But unlike Oxalis, which pulls up easily (thus giving me a false, yet satisfying, sense of accomplishment), wild onion snaps at the soil level every time I try to pull it up. So the entire plant must be dug up, which is difficult to do given the extent of its spread throughout the yard, its proximity to other more desirable plants, and the depth to which I must to dig. And I think that’s what I find so aggravating about the wild onion. I could quit work and dig wild onions for the rest of my days, but I’m still fairly sure that I will not prevail. It spreads so quickly and so thoroughly! So at best, I try to content myself with digging a few plants and snapping off the flower stalks so that the plants don’t spread even more via seed. I know there are worse weeds, but this wild onion is the one onion that makes me want to cry.
Close up of wild onion flowers. (photos by Erin Mahaney)
Note the cluster of white onion plants.