You can cut-down plants you don't want at soil level to help kill them without use of herbicides, yes, though if plants are a few years old they may have enough root-stored energy to resprout a couple of times. In that case, vigilant re-trimming will starve them out eventually. Young sprouts will probably be taken care of with one cutting.

Otherwise, you will need to either pull/dig them up or treat them with herbicide to kill the roots. When removing plants, try to either mulch the bare spot or replant with other species soon afterwards so the empty area or disturbed soil will not be readily colonized by weeds. For the future, since several hellebore varieties are known to self-sow and the problem may recur, it would be best to deadhead the plants after bloom each spring to remove developing seeds before they are mature. As with any weed prevention, discouraging germination with a maintained mulch layer between plants (or by planting densely enough that soil is covered) will help restrict their spreading nature as well going forward.

Miri

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