The Ongoing Battle with Burclover: Organic vs. Chemical Control

Photo of the prickly seed pods that stick to fabric and fur to spread from one lawn to another.

Burclover is a commonly used name for two prickly invasive clovers, Black Medic Medicago lupulina  and California Burclover Medicago polymorpha.  Since the beginning of the last drought we had, probably around 2007, my neighborhood has slowly been overtaken by burclover.  It is the tiny clover looking plant with yellow flowers and then prickly spiral shaped seed pods that stick to beach towels, picnic blankets, and dog fur.  I have been hand pulling it from the beginning, not wanting to resort to chemicals for control.  Each week, prior to mowing, I spend a  few minutes or so, going over the front lawn looking for any new signs of it to pull.  This time of year, it is slightly darker than my Bermuda grass so it is easy to spot.  At the neighbor’s house, I spot it even easier with all the tiny yellow flowers on larger established patches.

The pretty yellow flowers of the burclover make it easy to spot this time of year

My efforts to eliminate it have been futile, so much so it makes me want to cry.  I feel bad for George because he gets the burs stuck in his fur and it probably hurts when we comb or pull them out.  The whole neighborhood has it, with a few lawns on the block that look like all they have now is burclover.  It seems to be easily spread by the pets, the yard men, and the kids.  With the water restrictions, thin bare patches began to make the lawns on the block ideal for the burclover to take over.  After discussing it with the next door neighbors last month, we have decided to team up to each make a concerted effort to get rid of it over the next few seasons.  I compiled a page of control methods suggested by U.C. Davis ANR and Cooperative Extension to share with the neighbors.  It is at the bottom of the post.

Wednesday, I spread a giant bag of corn gluten all over the front lawn and parkway.  Although I spread compost on the lawn at least once a year, Corn Gluten is a natural fertilizer that is also reported to have allelopathic properties to inhibit the growth of broadleaf weeds, like clover.  It wasn’t necessary to spread it out back since the burclover has never managed to get a foot hold. The chickens like to munch on any patches that manage to germinate.

 

A small area of lawn at one of my neighbor's houses. The burclover makes up a large portion of the turf.

U.C. Davis ANR and Cooperative Extension offer some “best practices for control,” for both organic gardeners like me that want to avoid synthetic chemicals and folks like my neighbors that just want to kill it by the easiest means possible, as long as it doesn’t pose a risk to the kids or pets, and be done with it for half a year. The following is an excerpt from the page I shared with the neighbors:

MANAGEMENT OF BURCLOVER
Clovers are relatively easy to control in the home garden by hand-pulling, cultivation, and the application of mulch. In large, landscaped areas herbicides may also be necessary. Because clover seed has a hard seed coat that is very heat tolerant, composting and solarization are not as effective in reducing clover’s seed viability as they are with other weed species. The hard seed coat also allows the seeds to survive longer in the soil than many other weed seeds; clover seeds can germinate over many years, making the control of these plants an ongoing effort.

Once clovers are controlled, change cultural practices in the landscape and turfgrass to reduce the chance of reinfestation. Insuring a thick stand of grass can help exclude clovers in the lawn. Lack of nitrogen fertilization can also influence clover growth.  Adjust the fertilizer program to include more nitrogen and less phosphorus in turfgrass.  Mulches can be effective in excluding clovers and other weeds in landscapes.

ORGANIC CONTROLS
Annual clovers can be easily controlled by hand-pulling, hoeing, or cultivation. Mulching, depending on the size and depth of the mulch, can prevent seedling establishment. Before seeds germinate, a 4-inch thick organic mulch (e.g., compost, wood chips, etc.) can prevent establishment of clovers. Organic mulch can also be applied after the seedlings have germinated but must be applied in a thicker layer (4 to 6 inches) and must cover the plants completely to block out all light. Organic mulches need to be reapplied each year to maintain the 4-inch-thick layer because they decompose and the thickness of the mulch declines over time. Woven black landscape fabric can exclude weeds over a number of years. Larger plants are more difficult to control with mulching, but they can be hand-pulled or hoed.

CHEMICAL CONTROL
Post-emergent Herbicides
Both established annual and perennial clovers can be controlled with postemergent herbicides. The best herbicide to use depends upon the species of turfgrass. Warm-season turfgrasses such as bermudagrass, zoysiagrass, and kikuyugrass will tolerate products containing mecoprop and dicamba but not triclopyr. Cool-season turfgrasses will tolerate all of the herbicides that control clover. The herbicide 2,4-D is not effective for clover control; it will injure the plant but does not control it.

Preemergent Control
Preemergent herbicides available for landscape use are effective but generally unnecessary in the home landscape where annual clovers are easily controlled by the methods mentioned. For landscape professionals, herbicide formulations that contain isoxaben are effective for controlling annual clovers and can be used around many woody shrubs and trees. Most established annual flowers tolerate this herbicide. Herbicide formulations containing oryzalin, trifluralin, or pendimethalin will control most grass species and some broadleaf weeds but will miss many other broadleaf species, including legumes like burclover.

 

© 2012, .


Comments

The Ongoing Battle with Burclover: Organic vs. Chemical Control — 11 Comments

  1. What an informative post. Years ago when the marathon lawn that we had was getting really weedy and we found out the only way to irradicate them was with strong stuff including arsenic, we plugged in St. Augustine. It is a tough lawn that does not tolerate many weeds and takes less water than other lawns. I am in So Cal too. Thanks for all the info. I do see a couple of those in my lawn but not often. I think all the gardeners everyone uses spreads these weeds now. No one mows their own lawn any longer keeping their weeds contained in their yard. We do so maybe that helps.

  2. I have had issues but nothing to the extent that I saw in the photo. I do use a “weed and feed” fertilizer about once every two to three years to take care of the issue. I know organic is a way of thinking, but even “doctors” have to issue prescriptions every once in a while. If it is affecting your pets, I would certainly consider taking the treatment to the next level. Keep the posts coming, I really enjoy your blog.

  3. It has now been a few years since your neighborhood waged war on the clover. How is it going?
    I knew about burrs in the grass when I was growing up and discovered that we had it at this new house last year. It wasn’t until I was weeding in my front yard this year that I realized that the clover I thought was harmless was really the culprit. Now I am waging war!!! What was your most successful treatment plan?

    • With the drought, the burclover still persists in the dying lawns’ bare areas. Lush lawns have few spots for seeds to germinate. One neighbor treated multiple times with herbicide, replaced broken sprinklers, and reseeded the lawn. She has some burclover, but much less than she used to. The neighbor on the other side treated with herbicide once, waters the lawn lightly but frequently, and the burclover is everywhere these days. The dog tracks a few seeds every year from that lawn to ours. I have kept it under control with hand pulling. I have about the same amount of burclover each spring as the neighbor that renovated and diligently applies herbicide annually now in late fall. I examine our lawn for new seedlings prior to mowing each week and hand pull any i find. Therefore, I think both herbicide and pulling are equally effective, but it is a constant fight or the burclover comes back, well unless all surround homes get rid of it. With the lack of rain this winter, I am guessing our lawn will be dead sooner than in past years.

      • Thank you for the update. I am going to start the good fight tonight even though the plant has already gone to seed here. I may be seen vacuuming my lawn with our shop vac tonight because so many of the burrs have already broken off when I was pulling yesterday. I really want those suckers gone for my toddler’s sake and for the sake of our poor dog.

  4. Quick questions: What tool are you using to help pull up the roots of the clover? Just a regular spade?
    Do you dig about an inch or two from the base? Closer or further away?

    • Kathleen,
      Actually, I use my hand most of the time. I try to do it a few days after whenever we get rain, or if I turn the sprinklers on, I do the next day so the soil is soft, just before mowing. After mowing the burclover is harder to spot. I make sure to find all the leaves/ stems on each individual plant and gather them all together in my fist and pull slowly trying to get the thin tap root. If it breaks off, or if the soil is bone dry, I use what I think is called a dandelion fork or dandelion weeder. It is inserteded about 4 inches down into the center of the plant and used to pry it out while trying not to disturb too much surrounding turf. I am sorry but I am not 100% sure that dandilions fork is the actual name. I got it 20 years ago from my mom. It looks like screwdriver with a forked tip and a wooden handle. It’s great for pulling dandelions. On a side note, the chickens and tortoise love it when I pull dandilions out of the front law for treats for them in the backyard.

  5. I have a rule in my yard that I have to pull burrclover as soon as I spot the yellow flowers and put it in the trash can (NOT the compost heap!). In the spring I can pull it with my hands. My theory is not that it won’t come back from the root, but that I won’t let it go to seed. This has worked pretty well for me, but my boyfriend has a whole acre that doesn’t get watered in the summer (he’s on a well), and the burr clover has taken it over.

    There is also a slightly different weed that looks like clover but has small bluish white flowers and makes a different type of burr. I can’t find a name for it online and am wondering whether it could be a hybrid of the yellow burr clover with white clover. Or maybe it is subterranean clover.
    We thought it was regular white clover and were letting it grow, but when since the seeds came on they are a big nuisance. The burrs look like several small seeds in a cluster, each of the small seeds having a spine. Can anyone tell me anything about this plant and how to get rid of lots of it?

    Thanks.

    Martha

  6. Thank you so much for the info!!! Exactly what I have been searching for; along with what CA natives are good to save and spread! I was wondering though, where do you get ‘corn gluten’? I have never noticed it, & by a quick search, walmart doesn’t seem to have it!
    Thanks!

    • I had trouble finding it when I first tried using it more than a decade ago, but for at least five or six years I have seen it at most independent nurseries. Other places like home de pot or amazon carry it too, but per pound, its more expensive. Look for a brand named “Concern”. Its not cheap, probably twice or three times the price of chemicals.

  7. i live in south Louisiana, and everyone in town has this burrclover! I can’t take my little sish-Tsu for a walk, as he gets full of the burrs. Do they ever go away? or am i going to have to put up with them until winter? The flowers are not yellow on the clover, but white, and the burrs are flat. I am so tired of picking them out of my dog. even when we go to the park, they are in the st. augustine grass. I thought about seeding with bermuda, but on your blog, i see they grow in burmuda also. My yard is much too big to pull out by hand, and i really don’t want to use chemicals, as i am afraid they will hurt my precious dog.

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