Answer: If you aren't finding any insects on the plants, I suspect that the culprits are slugs or snails. Since ligularia grows best in moist soil and shady conditions, places where slugs and snails like to hang out, I'm even more convinced. You can use products like Sluggo or make some traps out of terra cotta pots. Begin by immersing the pots in water until they are completely saturated then set them upside-down in the garden near your plant, propping up one side of the pot with a stone. Slugs and snails will crawl in overnight. In the morning simply scrape them out into the trash and reset the traps.
Best wishes with your garden!
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