This is a stanza about a plant; this is clear from the context and from the word secg, which means a sedge or reed. It also means a person, poetically, and a sword. In Beowulf it is a sword: ac wit on niht sculon secge ofersittan, gif he gesecean dear wig ofer wæpen (but we two are obliged to abstain from the sword in the night, if he dare seek battle without a weapon.) I translate secg as sword to enhance the riddling nature of the stanza. Of all the plants, a sharp sedge is the most sword like. It’s got edges like razors and will cut you just like that. This one in particular will give you grim wounds, with burning bloody blisters. Stay away, don’t grab hold of it. Like the thorn, this plant wants you to bleed.