A gardener grafts two different roses together, and the result is a new bloom that outshines either original. That image becomes a way of understanding the speaker’s own mixed, conflicted inheritance. Where she might have felt torn by “warring blood,” she instead sees separate streams flowing together into one powerful current.
The feeling is not shame or confusion but surprise and pride. The poem moves from the careful, gentle act of grafting to a rush of “new-born forces,” so the mood feels alive and forward-moving. There is tension in the word “warring,” but it resolves into energy: difference is not erased, but fused into something more gorgeous than any single source.