Lesser Celandine Alert!

It's time for the annual call to action to prevent lesser celandine from taking over all of Princeton. Also called fig buttercup, it's a highly invasive nonnative plant that is spreading rapidly, yard to yard and into parks and nature preserves, where it degrades habitat for wildlife. It thrives on homeowners' indifference and inaction, so I've been doing what I can, urging town officials to defend our parks and preserves, urging homeowners to take action in their own yards, explaining that herbicides are not anti-nature if they are used selectively and medicinally. My letter to the Town Topics and other local publications starts like this:

Blooming in many people’s yards right now is a small yellow flower that, upon closer inspection, proves not to be a dandelion. Variously called lesser celandine or fig buttercup, its radical invasiveness triggers a predictable progression of emotions in the homeowner. Delight at its pretty flower soon turns to alarm as year by year it takes over the yard, spreading through flower beds, across lawns and into neighboring properties. What may start as a few scattered, harmless-seeming clumps quickly becomes the equivalent of a rash upon the landscape. Unlike the dandelion, lesser celandine also spreads into nature preserves. Poisonous to wildlife, it forms thick stands reminiscent of pavement. Over time, our nature preserves become less and less edible to the wildlife they were meant to support. Native diversity shifts towards non-native monoculture.

Below are some photos to help with identification, and here is a link that includes suggested means of stopping it from taking over your yard. Though the link says only to spray through early April, I'd suggest that spraying is helpful for as long as its leaves are green. Lesser celandine is a spring ephemeral, meaning that it comes up early, then dies back in June, going dormant until the next spring. Gardeners who like to dig up plants of this or that to give to friends should be aware that, if their yards have been invaded by lesser celandine, some of it may hitchhike in whatever plants they dig up later in the season to give away. They may unwittingly be giving a fellow gardener the beginnings of a major headache.

Lesser celandine is poisonous, and yet some websites declare it edible and offer recipes. Why the contradiction? Apparently, lesser celandine accumulates toxins later in the spring. The toxins break down during cooking or after drying. Still, one takes one's chances trying to eat it, and, alas, wildlife don't cook.

I've seen bees collecting pollen and nectar from the flowers, which is all fine and good, but this doesn't compensate for the inedibility of the leaves. The invasion of our lands by nonnative plants that wildlife don't eat essentially shrinks the acreage of functional habitat in Princeton, even though a great deal of open space has been preserved. Thus the need for management.

Given that some areas of Princeton have been overrun by lesser celandine, it's important to defend those areas that have not, by closely monitoring and spot spraying where the plant is just starting to move in. Invasions begin with just a few plants here and there. An absolute minimum of herbicide is needed to easily defend these areas. Lesser celandine can easily be distinguished from dandelion. Walk the grounds before the grass gets mowed in the spring and while the plant is blooming. For lawns, a product like Weed B Gone works. For other areas, a 2% solution of glyphosate does the trick. Since glyphosate can take a week to show visible effect on the plant, it's best to spray early in the spring so that there's time to see results and spray any areas missed. For those near wetlands, wetland-safe formulations of glyphosate are available, so Roundup is not the only option.

In terms of aesthetics, lesser celandine's dense, exclusionary growth does to the landscape what people badly afflicted with narcissism do to social situations. A woodland that once hosted a diversity of native wildflowers becomes, when overwhelmed by lesser celandine, one species' declaration of Me! Me! Me! 

Here's what it looks like up close.

Here's an example of the blotchy appearance an early invasion creates on a lawn. These blotches expand until the whole yard is coated.

The closest lookalike in the lawn is the violet, whose leaves are darker, more curled, and more toothed along the edges. 

Lesser Celandine Spreads Through the Neighborhood

It sure is pretty, but beware. It will take over your garden and your lawn. Too much of a good thing--it's the dominant story of our time, whether it be carbon dioxide in the air or a pretty wildflower spreading along the curb.

Lesser celandine (Ficaria verna), also called fig buttercup so as not to confuse it with the native celandine poppy, has essentially paved whole valleys. It's poisonous, and no wildlife have adapted to eat it, giving it a big competitive advantage. The most dramatic local examples are in Pettornello Gardens over at Community Park North, and downstream areas in Mountain Lakes. I've been watching it spread into the neighborhood one block from my house. Homeowners think it pretty at first, then feel distress at its aggressiveness.

Best to knock it out when it first arrives, with 2% glyphosate (wetland-safe formulation recommended when close to streams and wetlands). Digging it out is fraught with risks, as it spreads via small underground tubers, and probably via seeds as well.

Visiting my former home in Durham, NC, some years back, where it has only recently appeared, I found it growing in a couple adjacent yards, poised to spread via runoff into the local watershed. We asked the homeowners for permission to knock out the infestation. One neighbor agreed, while the other refused, indifferent to the impact her infestation would have when it inevitably spread beyond the boundaries of her yard. I had tracked another infestation elsewhere in Durham back to a homeowner's yard. He was grateful to find out what the plant was, and promptly eliminated it, as well as some he had given to his daughter in yet another watershed, thinking it was pretty.

These sorts of experiences put the lie to allegations that invasive plants are already so numerous that it's not worth trying to stop their spread. On the contrary, these plants' negative impact can be greatly reduced at the local level through timely action.

Winter Aconite and Fig Buttercup (lesser celandine)--Related Flowers, Contrasting Behaviors

Both of these non-native wildflowers are in the family Ranunculaceae. Both bloom early and have pretty yellow flowers. While one appears to be modest and highly local in its spread, the other spreads so quickly across yards and into neighbors' yards and floodplains as to pose a threat to gardens and natural areas alike.

Here's winter aconite (Eranthis hyemalis) opening up a week ago in my garden, a legacy from the previous owner. Its modest spread is easily contained. I've never seen it spreading into nature preserves. Note the leaf shape, which distinguishes it from the related wildflower below.

Update: For comparison, here is one of the first blooms of lesser celandine in 2021, on March 30. Note the shape of the leaves, which are "entire" rather than lobed. Just to confuse things, lesser celandine is also called fig buttercup, and its latin name Ranunculus ficaria has apparently changed to Ficaria verna. 

People think lesser celandine is pretty, transplant it to their gardens, then begin having regrets as it spreads uncontrollably to dominate their gardens and yards. If you are one of the distraught gardeners wishing you didn't have this flower, and not wanting to impose its spread on the rest of the neighborhood, late winter is the time to deal with it. 

Other posts on this subject can be found on this website by typing "celandine" into the search box. A post called "Will the real lesser celandine please stand up--a confusion of yellows" helps with identification.

Though I'm no fan of herbicide, that tends to be the only workable option in the majority of cases. I'm no expert on herbicides, but have been told that for lawns, a broadleaf herbicide like Weed Be Gone is effective. For flower beds, a 2% formulation of glyphosate (Roundup or equivalent) works well. Monsanto doesn't hold the patent any longer on glyphosate, so it's possible to buy if from other companies on the internet. I use a wetland-safe formulation, but for most yards, away from wetlands, some spot spraying with Roundup or equivalent should be okay. The plant itself is poisonous to wildlife. 

There have been other proposed means of killing the plant: 

Mulch

If you blanket the whole infestation thoroughly with mulch, e.g. a layer of cardboard covered leaves or hay or woodchips, it might kill the lesser celandine if you mulch as soon as the plants leaf out in late winter. Chances are, you won't cover it soon enough, or you'll miss some spots, and the lesser celandine will benefit next year from the fertilizer in the mulch. 

Vinegar/salts/detergent

This concoction has shown up on the internet: 1 gal white vinegar, 2 cups Epsom salts, 1/4 cup Dawn dishwashing detergent in a hand held 2 gal pump sprayer. Spray in bright sun on a windless day.

But I couldn't find evidence that it has been carefully tested, nor that it would kill the roots. If the roots survive, the plant will be back next year. The concoction contains an acid, and the salts are made of magnesium and sulphates. These may or may not be harmful to the soil if used to excess.