Best Methods For Managing Invasive Clover

Question: Hello again -- I live in Florence and am having difficulty managing invasive clover (weeds) growing among my ground cover plants. I have a large raised bed area planted with low-lying Asiatic Jasmine. I have no problem pulling occasional weeds from this area. However, despite my best efforts, some type of clover has become invasive and is now growing among the roots of the Jasmine plants (see photo of the Jasmine, the clover infested Jasmine, and a close-up of just the clover). This clover is so imbedded that it is nearly impossible to completely remove from the Jasmine without destroying the Jasmine plant. Obviously, routinely pulling out the clover has not been adequate control. Previously, you folks have been very helpful in responding to my inquiries. At this point, I am open to any suggestions or treatments you can offer to better manage this problem. Thanks so much, Dr. Norm Andross

responder: Bill Hutmacher  Replied June 27, 2024, 8:29 PM EDT
response: Hi Dr. Andross - Thanks for your question.  I too have this problem weed that keeps popping up where I don't want it.  This weed is called Creeping Woodsorrel.  It has two variations - Oxalis corniculata has greenish leaves and Oxalis corniculata var. atropurpurea has purplish leaves with yellow flowers.   It definitely looks like a traditional clover and is, as you well know, very persistent!  Here is some information on this weed with some options to try to control it - https://ipm.ucanr.edu/PMG/PESTNOTES/pn7444.html. Check out the Management - Landscape Plantings - Creeping Woodsorrel section for control suggestions.

responder: The Question Asker Replied June 28, 2024, 11:38 AM EDT
response: Good morning Bill,   Thanks for the detailed information. It seems the best options for managing Creeping Woodsorrel require me to be much more tenacious than these pesky plants. I’ll first try extra diligent weeding and then look into controlling the germinating seeds.   Part of my reason for contacting you was for a recommendation on an herbicide that will defeat the Woodsorrel without harming my Asiatic Jasmine. Obviously, I must rule out defoliants like RoundUp or Finale.    Can I assume the suggested list of preemergent herbicides offered in the article will not harm my Jasmine? Based on your personal experience, can you suggest a specific herbicide you have found that will successfully get at these weeds but not harm my bedding plants?   Thanks again for your guidance here, Norm   From: ask=<personal data hidden> On Behalf Of Ask ExtensionSent: Thursday, June 27, 2024 5:29 PMTo: Norm Andross <<personal data hidden>>Subject: Re: Best Methods For Managing Invasive Clover (#0144107)

responder: Bill Hutmacher  Replied June 28, 2024, 3:17 PM EDT
response: Good morning Norm - Diligent weeding is the way to handle the existing weeds in and around the jasmine as any broadleaf herbicide will damage or kill the jasmine too.  Here is some information from the Pacific Northwest Weed Management Handbook about weed control in home landscapes - https://pnwhandbooks.org/weed/horticultural/home-garden-landscape-management/management-tactics.    Take a look at Chemical Control Strategies #1 Preemergent herbicides applied selectively to soil.   Take note of the section on using corn gluten meal.  I have used it in flower containers on my deck and it has helped to prevent weed seeds from growing.  You do need to reapply at times after rain for example.   It is a non-chemical method to try.     If you do try out one of the preemergent herbicides listed in the PNW handbook, please read and follow all label instructions.  Make sure it is listed as safe for your existing plants.   If the label  doesn't list your plant specifically, it strongly recommends testing it out on a small sample area to check for toxicity.  Best of luck with your weed battle.  Regards,  Bill

responder: The Question Asker Replied June 28, 2024, 5:30 PM EDT
response: Hey Bill,     Great info. I’ll do as you recommend and carefully follow directions to avoid trading one problem for a bigger one.  Many thanks, Norm   From: ask=<personal data hidden> On Behalf Of Ask ExtensionSent: Friday, June 28, 2024 12:18 PMTo: Norm Andross <<personal data hidden>>Subject: Re: Best Methods For Managing Invasive Clover (#0144107)