Plants that are in Burgundy’s speech (H5), Ophelia’s garlands (Hamlet) and Lear’s coronet (King Lear):
Burgundy: Vine, darnel, cowslip, hemlock, fumitory, burnet, clover, dock, thistle, kecksy
Ophelia: crow flower, nettle, daisy, long purple, bough, weed
Lear: Fumiter, furrow-weed, idle weeds, hardock, hemlock, nettle, cuckoo-flowers, Darnel.
What immediately strikes me about these plant-heavy passages is the lack of overlap. Darnel and fumiter are the only ones repeated, and those repetitions are peculiar to these passages. (Fumiter is mentioned only in H5 and Lear, while darnel is mention in H5, Lear and H6.1.)