Lesser celandine is back: What to do if it’s already out of control

by Connie Oswald Stofko

I have been writing about lesser celandine for 11 years, but I realized I hadn’t addressed in detail what to do if your whole yard, or a large section of your yard, is covered with lesser celandine.

Here are questions I got from a local gardener:

Hi Connie,

I bought a new house last spring in the Elmwood Village (area of Buffalo). It’s beautiful but both the front and back yards are total carpets of lesser celandine and I know we are just approaching the window for the year to tackle it.  

I wanted to see if you have been able to confirm the solarizing method actually works on lesser celandine? Anything important to know about clear tarp vs black, etc? I’ve read a great deal but don’t seem to be able to find conclusive info. 

My thought was to spray glyphosate this week, then tarp it for the entire summer.  It’d be a long, ugly summer, but hopefully worth it.

Thanks!

Tom Murdock

Well, Tom, glyphosate (an herbicide) can work. Smothering the lesser celandine can work, too, but you’ll have the tarp on your lawn longer than you thought.

Background on lesser celandine

If you’re not familiar with lesser celandine, here are the basics:

• You don’t want it in your garden!
• It can take over your lawn!
• Lesser celandine has a pretty flower, but don’t let that fool you. It’s a bad plant here in Western New York.
• The leaves are coming up now.
• Now is the time to take action to get rid of it.
• If you do nothing, around the middle of May, you will think it has disappeared, but it hasn’t! It has just gone dormant and is waiting to come back in even larger patches next year.
• It’s an invasive plant and is bad for wild areas, too. It can spread from your yard to wild areas.

These articles will get you up to speed:

• It’s pretty, but invasive– Get rid of lesser celandine (2013)
• Get rid of lesser celandine– It’s pretty, but it will take over your lawn (2016)
• Kill lesser celandine before it flowers; look for it now (2020)

“Whatever you do, don’t ignore it,” said Lyn Chimera of Lessons from Nature.

How to deal with large areas of lesser celandine

There are several things you can try to get rid of lesser celandine.

• Digging. If you have just a few patches of lesser celandine, dig it up before it spreads. Find out how to dig up lesser celandine correctly. If it already covers your entire yard, you might want to try something else.
• Solarization. If you’re desperate, you can try it, but it probably won’t work.
• Smothering. Local gardeners have said it works.
• Herbicide. Lesser celandine is one of the rare cases where an herbicide is recommended by environmental professionals.

Solarization

A WNY gardener, whose lawn was seven-eighths covered in lesser celandine, was desperate. In 2016, she asked if there was anything new that she could try.

I talked to Carol Ann Harlos, Master Gardener, garden writer and speaker. No, there was nothing new, Harlos said, but if you have a large area to kill and are desperate, you could try solarization. Harlos hadn’t read about solarization being used on lesser celandine and didn’t know how effective it would be.

The idea is to kill the tubers (roots) with heat. You could lay down black plastic and perhaps the sun would heat the ground enough to kill the tubers.

Checking back with her this week, Harlos said she doesn’t think solarization will work. The soil temperature would have to heat up several inches below the surface.

A clear plastic tarp probably won’t warm the ground at all, Harlos said, but black plastic probably won’t warm the soil enough.

Another drawback to this method is that a 30 by 30-foot plastic sheet costs more than $100, said Tom Murdock, who asked the question at the beginning of this article.

Smothering

Lyn Chimera of Lessons from Nature suggests smothering lesser celandine with layers of newspaper and cardboard. Chimera described the process here for killing lesser celandine in a garden bed.

You could use that process on a lawn, too. That would leave you with the area covered in paper and cardboard, then covered with mulch to look better.

When I talked with Chimera this week, she emphasized that timing is crucial. Lay down the paper and cardboard now, before the plants bloom. Add mulch on top.

Keep those materials in place for the rest of this year and into next June.

If you pull the cardboard up at the end of summer, as the questioner, Tom Murdock, wanted to do, or even wait until early spring next year, “it will have done no good at all,” Chimera said.

Remember that lesser celandine is a spring ephemeral. It leafs out now, flowers soon, dies back around the end of May, then lies dormant until next year. Keeping the cardboard in place until June of next year will have smothered the lesser celandine for two growing cycles. You could take the cardboard off in June of next year, or keep it in place until August, which is a good time to plant grass.

While Chimera relied on digging to get rid of lesser celandine in her landscape, she has heard from local gardeners who have successfully gotten rid of lesser celandine by smothering it.

Herbicide

While we hate to use herbicide, it is effective on lesser celandine.

It must be applied now, in early to mid-April, said Andrea Locke, coordinator of WNY PRISM (Partnership for Regional Invasive Species Management). If you wait until you notice the flowers, it’s too late–the herbicide won’t work.

Common active ingredients found in herbicides for lesser celandine are triclopyr, glyphosate and dicambia, she said. You can find these herbicides in garden centers and other stores.

Follow the directions carefully when using any herbicide.

UPDATE: Andrea Locke sent this sheet on control options for lesser celandine.

How to get your gardening questions answered

Sometimes readers contact me with questions that I can’t answer. I’m not a gardening expert– I’m a writer by profession. I interview knowledgeable people in order to provide you with great articles on Buffalo-NiagaraGardening.com.

If your plant isn’t growing well or if you don’t know the name of a plant or an insect, get expert advice from the Master Gardeners with Cornell Cooperative Extension and the staff at your local garden center.

But sometimes quirky questions come up. These are questions that readers might be able to address.

Sending a question to me to post can be helpful if you’re looking for a wide range of opinions and don’t mind waiting for the answer. If you want to try this route, email the question to me at connie@buffaloniagaragardening.com and I’ll pose it to my readers in an upcoming issue.

See some gardening questions and answers here.