Lesser celandine creates a dense carpet of vegetation that smothers other species. Its ability to reproduce vegetatively by means of bulblets that scatter as the foliage dies back, plus seed from pollinated flowers, make it an aggressive spreader. Bulblets are easily carried to new sites on flowing water, such as stormwater runoff and streams swollen by recent rains. Tubers can be unintentionally moved around in fill dirt and the root ball soil of transplanted perennials and shrubs.
Mechanical control
Lesser celandine can be managed without the use of herbicide, but the process takes more effort and time and may not be very effective. After the plants go dormant, the only way to remove the plants is by screening the bulblets and tubers out of the soil manually. Due to their small size and variable depth, and the requisite soil disturbance, this is not practical where lesser celandine has invaded lawns, garden beds, or wooded areas. The successful removal of established lesser celandine colonies may take many years of pulling or digging the plants out of the ground during the brief period of time they are actively growing.
Smothering a patch to deprive the plants of light might weaken them if begun promptly as soon as new growth emerges in early spring. Since lesser celandine sheds leaves when going dormant, as soon as flowering is finished and the foliage begins to yellow and wither, blocking light from the leaves will not sufficiently weaken the plant.
While mowing the leaves off could help weaken the plants, they usually grow too short to be cut by a mower (although a string trimmer used to selectively mow-down a patch may work). One risk of mowing is accidentally dispersing any bulblets present.
Chemical control
A systemic herbicide applied to the leaves will be absorbed and kill the roots. This process takes time and may require repeat attempts to achieve full control. During the transition to dormancy and during dormancy, the plant is not affected by herbicide. Since there is a very limited window of time when herbicide will be absorbed by live foliage and take effect, it may take several springs to bring an infestation under control. The commonly-used systemic ingredients is glyphosate; follow all product label directions for use.
When using glyphosate, begin applications to lesser celandine foliage from about mid-February to early April, as long as the temperature is 50℉ and no rain is anticipated within 12 hours. Waiting beyond this period of time may cause damage to native wildflowers that emerge in the same habitat. In the mid-Atlantic, it is recommended to wait until half the lesser celandine plants in a colony are in bloom to start control.
Chemical control in lawns
Products containing at least two of the following active ingredients have been found effective; MCPA, triclopyr, or dicamba. Select a product labeled to manage broadleaf weeds in lawns, since they are designed to avoid harming the grass. (Glyphosate is non-selective and can damage any plant it contacts.) Use caution with these products near desirable plants and vegetable gardens, as the potential for volatilization (pesticide vapors moving through the air) exists in warmer temperatures. Dicamba in particular can cause serious damage to trees and shrubs. Always follow product label directions, weather precautions, and application rates.
The waxy, water-repellent quality of lesser celandine leaves may benefit from a surfactant (also called a spreader-sticker or adjuvant) added to the herbicide before application. This additive helps a spray remain on the leaf and resist dripping off so more of the chemical can be absorbed. Check herbicide label information for the product's compatibility with a surfactant; they are typically sold alongside pesticides in retail stores.
