Culpeper gives rosemary to the Sun, noting its action on the head and the memory, the Sun in his scheme governing the vital spirits and the higher faculties. That is the sourced attribution.
Rosemary is then an unusually good illustration of how unstable this material becomes once it leaves the source. Later occult compilers variously place it under the Moon, on the dew-of-the-sea name and coastal habit, and under Mercury, on the association with memory and intellect. Each reassignment is internally reasonable and each is unsourced, and printed tables now circulate giving all three without noting that they disagree or where any of them came from.
There is a fourth placement with an actual citation, in a different scheme. Agrippa's fifteen Behenian fixed stars each carry a stone and a plant for talismanic use, and the plant paired with Alphecca, in the Northern Crown, is rosemary. That is a documented Renaissance correspondence, dated and attributable, and it is unrelated to the planetary rulership question.
The lesson generalises past rosemary. When a modern source prints a plant's planetary ruler without attribution, the reasonable default assumption is that it is Culpeper, possibly at several removes, possibly altered along the way, and that any confidence in the figure is borrowed. Where two sources disagree, at least one of them has changed it silently. Rosemary happens to be a case where the drift is easy to trace because the alternatives are each attached to a visible feature of the plant.