Hi,

Thank you for your question. 

Lesser celandine (Ranunculus ficaria), AKA Fig buttercup,  is a perennial herbaceous invasive spring ephemeral. If your lesser celandine is going dormant, you may continue to  dig out patches.  Beyond that,  you may want to wait until next year to resume eradication because dying foliage is not effective at moving the herbicide application into the roots.  Small clusters may be dug out making sure that you remove the entire plant including the tubers. Lesser celandine dies back in the summer,  so glyphosate should be applied in late winter or very early spring if the temperature is above 50 degrees. Since lesser celandine likes damp woodlands or wet areas another reason to  treat it in early spring is to spray  when the temperature is right but before amphibians and insects have emerged. Please follow label directions and safety precautions when using herbicides.

Christine 

Hello Paul,

The ingredients in the pesticide you mention are not systemic, so they cannot kill roots or move throughout the plant in its sap the way glyphosate does. (Glyphosate is usually the main or only active ingredient in Roundup, but some formulations of Roundup may be made differently, which is why we focus on the active ingredient.)

Cornmint oil might "burn" the foliage off of weeds, but perennial weeds can regrow, and a waxy-leaved weed like Lesser Celandine might not even get a dose large enough to cause much damage since the foliage is naturally water-repellent. (Oil might adhere better, but we have not tested this ingredient.)

The primary use of the geraniol ingredient is not as an herbicide, though it can be when part of geranium oil extract, which includes a couple other chemicals.

In all, the product you are asking about would probably be no more effective at killing perennial weeds than horticultural "vinegar" (more accurately called acetic acid) and other contact-only ingredients. Even though a systemic like glyphosate will still probably require more than one application to effectively combat Lesser Celandine, a type of contact herbicide would need even more applications and would take much longer to work (if it works at all).

Given the water-repellent leaves on Celandine, you may need to add a spreader-sticker to the spray so the liquid adheres better to the leaf and has more time to be absorbed. Check the glyphosate label before doing so, in case the product chosen is either incompatible with such an additive or already has that type of ingredient component in the mix. Spreader-sticker products are sold alongside pesticides in garden centers, and they have their own product labels that need to be followed. Treat the Celandine soon (at or close to peak bloom) for maximum efficacy, because treated too long after bloom, no herbicide will have any effect since the plant rapidly goes dormant.

The "toxicity" of Roundup is still being debated scientifically and studied. Complicating matters is whether or not studies are taking into consideration the active ingredient alone (glyphosate in this case) or the entire product. Like most pesticides, it will contain "inert" ingredients in addition to the active ingredient(s). The word "inert" does not imply safety; rather, it simply means that those ingredients are not the ones controlling the pest directly, but they can aid in the product's absorption, longevity after application, or they contribute to it being shelf-stable or easier to apply. How these mixes interact with factors like temperature, moisture, sunlight (like UV light), and soil microbes all contribute to how rapidly and fully any pesticide breaks down after being applied outdoors, organic or otherwise.

Glyphosate is known to bind tightly to soil particles (not that it's applied to soil, since that's not how it works, but there may be overspray or drips), and thus poses less risk (barring erosion problems) of contaminating other areas because the chemical does not move off the treatment site. Other systemic ingredients pose a higher risk of groundwater contamination or possible root absorption by nearby plants if they bind less to soil or dissolve more in water. As glyphosate degrades, it turns into byproducts that can be eclipsed in toxicity by many other compounds (including simple table salt). Since different brands and product formulations can use different combinations of inert ingredients, however, even two different products using the same concentration of glyphosate may still have different environmental breakdown rates or impacts. Even the microbial diversity of different soils can impact how rapidly or fully any chemical breaks down, even those that might break down faster overall like various organic, naturally-derived, and/or lower-risk ingredients. As long as the all of the label instructions on a EPA-registered pesticide are followed, the product will be as low-risk to people and the environment as possible.

Miri

You're welcome!