Treating Lesser Celandine: We test 14 control methods to show what works and what doesn't.

Lesser Celandine (Ficaria verna), also called Fig Buttercup and Pilewort, is a highly invasive, non-native plant in the eastern half of the United States. It is a perennial that is very difficult to control once it gets established. If you do a search online for ways to control it, you find a wide variety of suggestions, but not a lot of evidence on how successful each method is. We established over fourteen test plots in early 2021 to test some of the methods to see what works. We tracked each method for a year to see which methods are truly useful, and which methods just look good for the short haul, but don't do anything to reduce the number of Lesser Celandine plants.

We looked at mechanical means such as mowing, burning, and mulching with both clear and black plastic. We also tried some “environmentally friendly” chemical methods such as treating with 5%, 15%, and 30% vinegar (acetic acid), and 1.5% chelated iron. Our tests showed that all of these methods just impacted the above-ground portion of the plants and did nothing to kill the extensive roots and tubers underground. We also tested 4%, 3% and 1.5% of the non-selective herbicide glyphosate (ShoreKlear Plus), and 12%, 6%, and 3% of the broad-leaf herbicide triclopyr ester (Alligare Triclopyr 4). All concentrations of glyphosate were successful at killing off all of the Lesser Celandine after one treatment. The test plots treated with glyphosate had full coverage of non-target vegetation two months after treatment, showing that the glyphosate only killed off the vegetation that was leafed out at the time of treatment. The three dilutions of the triclopyr were successful at killing off the Lesser Celandine after one treatment, but the concentrations were high enough to also kill off all the other vegetation in the test plots throughout the first growing season. (We are running new tests on different concentrations of the triclopyr ester, along with trials with the triclopyr salt and other broad-leaf lawn formulations. Watch for videos with those results in the summer of 2022 and the spring of 2023.)

Our conclusion is that successfully controlling Lesser Celandine involves: 1) keeping it out of a site by not intentionally planting it or unintentionally introducing it through mud or dirt on shoes or equipment from infested sites, and 2) treating it as soon as possible with an appropriate herbicide. While many people are reluctant to use herbicides, the environmental consequence of allowing Lesser Celandine to continue to spread and choke out native vegetation makes the careful use of herbicides the most environmentally friendly choice. Glyphosate has a relatively short half-life in the soil, does not migrate easily through clay soils, and does not kill any plants that it does not come in direct contact with the leaves. It does not kill through root uptake. While there is still more to learn, it is nice to know what methods are not worth our time and effort.

Oak Haven is a 60-acre private woodland in Southwestern Ohio near Cincinnati. Jim and Julie Varick both have degrees in Botany and over thirty years of experience in managing natural areas. They enjoy sharing their enthusiasm for the natural world and would like to build relationships with like-minded people to share knowledge and resources.

[CamillaSeth]

I love that you did this. It's a crisis. This stuff is a cancer. I wanted to do this experiment - but you already did!!

[Andremmd]

Thank you for the comprehensive video and all of the hard work.

[susangajewski]

Thank you. I was digging it up. Now I see how CAREFUL I have to be about removing it. I'll use the herbicide.

[leeannefinke]

Thank you for taking the time to share this information. Very helpful, and we appreciate it!

[markjohnson-smif]

Great video. Thanks for the scientific approach. I live in Cincinnati and I'm treating the lesser celandine in my turf with Tenacity (mesotrione). This is the 2nd year of treatment and the infestation appears to be less than last year. 3% glyphosate works great in the mulched or wooded areas.

[ltgemini]

Cleveland. My yard is carpeted and it seems to have come outta no where. And it keeps raining. My new bed thats were established last year are COVERED.

[reneedekona]

Thank you for your thoughtful process considering the environmental impacts above all else!

[tedfinkenauer]

Outstanding video. We did a mechanical pull yesterday in the gardens. Going to hit the isolated growth in the lawn with glyphosphate today.

[hoverboverer]

Interesting. I live in the UK (where it is native). Couple of points: One approach you didn't try was competition: I had a large patch of celandine (that I was OK with) that declined drastically when I introduced wild garlic (Allium ursinum) to the area (that is, totally eliminated apart from at the edges of the growing Allium patch). Obviously don't recommend that in N. America but surely there is something native that comes into leaf early that can overshadow it? Another point is that the plant has a very shallow root system. I imagine removing the first inch or two of soil would be very effective. LOL at the ducks: In recent years Wood pigeons have decided to move in to my area and they are rampant herbivores. Turns out their favourite food in Lesser celandine - hardly seen a flower in the last few years! Even if you succeed, I suspect the celandine is spreading via that stream you have, so you would still have to keep an eye out for it, especially after floods.

[jameswinnett]

I'll be keeping my eyes open for it! Not sure we've got any, but don't want it either! Thanks for the informative video!

[ASolitaryHowl]

This is a very informative video, thank you for your hard work. Well done, especially like the more scientific approach.
Been struggling with a large patch for years, I think it's about time I use herbicide...even though I HATE the idea

[markjones]

Thank you so much for all the time, hard work, and thought that went into this. Very much appreciated.

[juliebruno]

Super, excellent, comprehensive. I don't have enough superlatives for this. I have been fighting this for 3 years and regret not using an herbicide - AND I ONLY USE HERBICIDES ON POISON IVY AS I AM SEVERELY ALLERGIC. I will share this in the same way that lesser celandine spreads. Thank you!

[kapa]

Thank you SO MUCH!!!! You saved me a ton of work trying to hand weed and dig it up by a spade, too much gets left behind. Do you have new updates to eradicating this thug? Mine came from the community mulch pile, never again!

[Laura_Darkspear]

Thank you so much for taking the time to make this video. I’ve been scouring the internet trying to figure out what is taking over my lawn and through all my searching I’ve found out that’s it is definitely lesser celandine. It has spread like wildfire and it’s become too much to pull by hand. I was looking for a solution and found your video! So thank you for your experiment and info! The celandine flowers have unfortunately already started blooming in the yard so I will treat it all when those are done I think. Unless it might be ok to cut them back by mowing and treat the area with glyphosate after it’s cut back. Any advice on that situation would be appreciated. Thanks again!

[richard-dfpr]

We looked at mechanical means such as mowing, burning, and mulching with both clear and black plastic. We also tried some “environmentally friendly” chemical methods such as treating with 5%, 15%, and 30% vinegar (acetic acid), and 1.5% chelated iron. Our tests showed that all of these methods just impacted the above-ground portion of the plants and did nothing to kill the extensive roots and tubers underground. We also tested 4%, 3% and 1.5% of the non-selective herbicide glyphosate (ShoreKlear Plus), and 12%, 6%, and 3% of the broad-leaf herbicide triclopyr ester (Alligare Triclopyr 4). All concentrations of glyphosate were

[tedmerr]

try superheated steam at about 180–200 °C

Farmers often do this to sterilize soil before sowing seeds.

[carolanndp]

This was very informative! Where can I purchase 3% glyphosate. Seems like most of the herbicides have a lot more concentration. Thank you for your help!

[adelafaith]

I have it in my garden in UK. It is everywhere! I dont like using herbicides and last year i tried weeding it out by hand (didn't work) This year trying turning the turfs over (made a patchwork, which now looks like soil!) and hoping it will rot into the ground.
Having watched this im going to try an area given over to strawberries as they've a similarly dense leaf; and an area covered with black plastic after the turning soil over, and strawberries grown through purpose made holes in the plastic.
Trouble is the seeds from several untreated years will still be in the soil and the flowers turned over into the ground may still set the seeds...?
(I didnt really want strawberries all over but having seen how invasive wild garlic can be and wild strawberries, felt cultivated strawberries would be worth trying a useful option.
I may try another area just trying to grow veggies and flowers for the summer..depends how i get on.( It's not a big garden but broken into chunks by winding path)

[khollen]

Thanks for a great video. I live in Connecticut and have a very bad case of Lesser Celandine throughout my lawn and wooded area. I believe it came from the water company property we border. So far have found nothing to get rid of it but have slowed it down slightly. I just treated the areas with Gordon’s SpeedZone Lawn Weed Killer, 652400 after having heard it might help. I'll let you know if it does anything to slow it down. Thanks again for testing and sharing your results.