Lesser Celandine Spreading Into Local Parks

Poisonous to wildlife, crowding out other plants, be they native wildflowers or turfgrass, lesser celandine spreads across sunny lawns and shady forests alike, forming dense, exclusionary mats that can extend far into the distance. 

I've written many posts about this highly invasive plant, and how it can be controlled with targeted, minimalist use of herbicide if one catches it early in one's yard or in a local park or preserve. Invasions start with one isolated plant like this, which can be easily sprayed with systemic herbicide without damaging nearby vegetation. (Or dug up and thrown in the trash, not the compost.) Of course, one plant looks harmless enough, but its rapid spread will change your view from "Gee, that's pretty" to "Help!!"

Incredibly, this spring I happened upon a homeowner in our neighborhood who actively sells lesser celandine and other plants she digs from her garden, apparently via facebook marketplace. Her garden is infested with the plant, and so this noxious weed will hitchhike in the soil of any garden flower she sells. Though it has a pretty flower, it's rapid spread will cause gardeners to lose control of their gardens, and to then serve as vectors for the plant's additional spread to neighboring lands. I asked the woman about the ethics of selling and intentionally spreading such an invasive species, and she refused to even discuss it. She blamed her unreceptivity on someone who had confronted her about it in an unfriendly manner. I asked "What if a nice person were to raise the issue with you?" But she still refused any discussion.

I may be having more success with Princeton parks. This spring, a friend, Mimi, was concerned about the status of the London plane trees along the Scott and Hella McVay Poetry Trail in Greenway Meadows, and asked me to take a look. The trees definitely need some attention, given all the invasive shrubs growing beneath them, but I also noticed that lesser celandine is beginning to spread through the park's meadow and lawn. 

Here's that classic "first plant" which would ultimately carpet the whole meadow with its poisonous foliage if not treated. 

And here's an early infestation in the lawn that extends down to the ballfields and into the land surrounding the DR Greenway Johnson Center.

I urged the town to take action, and it appears they will. 

This spring has not been ideal for spraying lesser celandine. Days have remained cool, which I personally like, but it's best for the temperature to reach 50 degrees for effective treatment. Of course, having just written that, I come upon a source that says at least 40 degrees. 

Glyphosate--much vilified for its overuse in agriculture--is still the most dependable systemic herbicide to use. If close to wetlands, a wetland-safe formulation (not Roundup) can be used, though it takes some sleuthing on the internet to find it. For foliage, a 2% solution is good, but some use 4%. 

I've heard that some land managers use an herbicide called Milestone, which may be a useful alternative, particularly because it doesn't harm surrounding grasses. 

If you read online about lesser celandine, you'll sometimes see claims that it must be sprayed very early in spring, before it flowers. Early spraying in helpful, but people should not be deterred from spraying later in spring as well. You'll also see claims that lesser celandine might be mistaken for the native marsh marigold. But marsh marigold is extremely rare. In all my explorations of Princeton's open space, the only marsh marigolds I've seen are the few that I have planted. 

Lesser celandine reminds us that we are all connected. What one person allows to grow in the yard can impact neighbors and nearby natural areas. The more a neighborhood becomes infested, the more likely it will spread to your own yard, through landscapers' mowers or on the hooves of deer. Thus, one person's problem quickly becomes other people's problem. It's important to be vigilant.