You can eradicate lesser celandine if you are persistent through several consecutive years. It’s important to realize that, if you stop for even one season, the plants will rapidly regain strength and re-set the battle to the beginning.
Your goal is to exhaust the plants’ resources stored in their roots. Depending upon the extent of the infestation, your options are several:
1. Dig, and repeat as needed, work best if plants are relatively few.
2. A systemic herbicide (weed killer) is the method of choice for more extensive infestations. Apply and repeat as needed; a paint-on method is the most effective application and is safest any desirable plants nearby. In this instance, timing is critical. “Start prior to flowering and up until about 50 percent of the plants are in flower, around April 1, then stop.” (See link below.)
3. Whatever your choice, you *must* follow-up by removing all stragglers as soon as you see them.
An excellent article about eradicating this pernicious weed is “Least Wanted: Fig Buttercup” at http://www.nps.gov/plants/alien/fact/rafi1.htm. The bottom line is, this is a difficult project, depending on how wide-spread the invasion is. It will require persistence on your part.
Nothing I see in this link, which confirmed what I know, in having to deal with this for the last 5 years, says anything about whether there are any herbicides that aren't as dangerous as RoundUp that might be effective for homeowners who are elderly and unable to get out there on their knees and dig this up or have an incinerator even if they do. So it goes into the garbage or yard debris can and I can only imagine this then becomes a problem in landfills and yard debris recycling plants.
We just had a windstorm here this week I was out digging this stuff up after the storm and found that a slat of my back neighbors fence had broken and I could now see into this elderly woman's yard, this is clearly the source, it's in full bloom and covers at least 60-80 square feet. I'm 67 and in ill health and it's all I can do to keep up my own yard, let alone hers. I talked to her about it and she understands, but is close to 80 and will try to contact her son.
I've built a screen to catch the corms as I dig them out and it works well. Have found that pulling the entire plant slowly while the soil is wet brings up most of the corms intact. This method is very time consuming and frankly pointless if pollen is just going to be blown into all of our neighboring yards by this neighbors healthy patch of it.
http://www.nps.gov/plants/alien/fact/rafi1.htm Your link. Not one of the links on this link opens up. They are all "Unavailable".
I regret the inconvenience these aggressive plants have caused. Every resource I located suggested glyphosate as the preferred systemic herbicide to effectively clear out lesser celandine. Glyphosate is safe to use when applied as a wipe-on application; it is inactivated with soil contact.
Sorry about the dead links in the page I referred you to. Unfortunately, dead links are far too common. As far as I can tell, these are the current links they refer to:
- National Invasive Species Information Center; Species profile for Fig Buttercup: http://www.invasivespeciesinfo.gov/plants/figbuttercup.shtml
- Invasive Plant Atlas of New England: http://www.eddmaps.org/ipane/ipanespecies/herbs/Ranunculus_ficaria.htm
- Invasive Plant Atlas of the United States http://www.invasiveplantatlas.org/
- Lady Bird Johnson Wildflower Center (Unlikely to be of use to you unless you want sources of alternative native plants.) https://www.wildflower.org/
I don’t know if the following agencies offer assistance to residential homeowners. If they don’t, they might have suggestions.
1. The Oregon Department of Agriculture classifies lesser celandine as a noxious weed. They have a noxious weed control program, so I would suggest contacting them for control options. This link has information on the weed and lists contact information for the program. http://www.oregon.gov/ODA/PLANT/WEEDS/Pages/profile_lessercelandine.aspx
2. Depending upon your location within Multnomah County, contact either East Multnomah Soil & Water District (503.222.7645) or West Multnomah Soil & Water District (503.238.4775).