Sagittata is one of those salvias which came in to Australia with no species name to start with so ‘Mosquito’ was suggested for its airy flowers on black stems. Betsy Clebsch in her New Book of Salvias said it was found in 1798 at very high elevations in the Andes. I always find it strange that high elevations doesn’t always mean the plant resists frost. It must surely come from the tropical parts of the Andes as the Pacific side from Peru down is incredibly dry with not a lot of vegetation.
Sagittata will grow bigger in sub tropical areas but with cooler temperatures it will be less than a metre in height and width. It self seeds and crosses with similar salvias. Sagittata is not suitable for frosty areas unless you are an expert gardener and want to protect it etc.
Since the first introduction of sagittata with its constant wonderful true blue flowers we have had rumicifolia which is similar but with a bit more violet in the flowers. Then we got macrophylla x sagittata which is a bigger plant again with beautiful blue flowers, then we got a shrubby macrophylla with purple backs to the leaves and inkier blue flowers This last one was called Big Swing in California I believe. Some of these are listed with the macrophyllas.