Oxalis - control hints, please!

Oxalis stricta (?) or common yellow oxalis annually invades my streetside ground cover plants for about six months, from November through May, and starves them of light, making for very spotty spring growth for the invaded prostrate rosemary, red apple succulent, myoporum, and miniature ice plant cover. They are persistent, nearly alien in their tenacity, and seem to spread by seed, rhizome, and bulblets, so pulling does little good, even in our soft loamy coastal soil in N. California. Since they die out from June to October, letting them take over means barren ground in the summer months. Is there any practical control solution outside of individually digging the thousands of plants? I would guess oxalis is in the clover family, but wouldn't clover control chemicals also damage my four ground cover plants? Thanks for any ideas!
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"Roger" <sherry roger at comcast dot net> wrote in message

roger, I have that (or similar) in my lawn though the oxalis is a very small leafed variety. Spraying it with a broadleaf spray knocks it back I have noted in previous years. Check with a garden centre about the susceptibility of your ground covers to the chemicals used. That is the cheap, nasty and easy way of doing it.
Maybe a more enduring solution is to find a ground cover that grows well over summer that can shade out much of the oxalis. Don't ask me what however something that grows well late spring and dies back early autumn allowing the other plants to take over. I have a succulent ground cover through some of my gardens (the succulent essentially took over) that does well keeping the weeds, including oxaslis, down. It does need a pruning every so often and is a year round cover so not ideally what you want.
rob
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Roger wrote:

Oxalis does not spread by rhizome, only by seed. If the ground covers were thicker, oxalis would be reduced. You could also consider adding wood chips by hand in the ground cover. That will be a total pain but it will give you a few years of respite.
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Thanks for your advice -
I just got an ID from my local farm bureau, and my oxalis is "oxalis pes-caprae". You can see it by doing a Google Image search for Bermuda Buttercup. According to online sources, it reproduces primarily by bulbs and less so by seed. Nevertheless, they give me little hope short of using pre-emergent twice in the fall. I don't wish to follow the chemical route, so I plan to replace my aptenia (red apple) , myoporum, and miniature ice plant, with a more robust and competitive plant. So far, my prostrata rosemary seems to to the trick and overcome the oxalis, especially when I use landscape fabric for the small seedlings.
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By the way, Oxalis seeds are not destroyed, even in the hotest compost pile, so do not try and compost oxalis when it has gone to seed.
John Henry Wheeler Washington, DC USDA Zone 7
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Roger wrote:

The long horizontal stems of oxalis will indeed take root if they touch the soil. The plant really does not have bulbs, but the tops of the taproots are swollen to a bulb-like appearance. The flowers form seed pods that open explosively when touched, scattering the tiny seeds to quite a disance. The seeds are sticky and will cling to your clothing, dropping off later to scatter the plants even farther.
There are spray-on herbicides that are specific to oxalis and also spotted spurge, containing ammonium thiosulfate. Oxalis and spurge are severely burned by this spray. If the foliage is completely wetted by the spray (add liquid soap to promote wetting), it will kill growing oxalis and spurge plants. Unfortunately, the seeds are not affected; so frequent respraying might be necessary.
The spray will not harm most other plants, but carefully check the label. Also ask at your local nursery (providing they have an herbicide expert on staff). I think it will damage junipers and some varieties of iceplant, but they should recover if not thoroughly wetted.
After a very few days, the herbicide decomposes. A by-product of decomposition is nitrate nutrients for other plants.
--

David E. Ross
<http://www.rossde.com/
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On Sat, 30 Dec 2006 11:59:03 -0800, "Roger" <sherry roger at comcast dot net> wrote:

k
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