] I read it this way too, but am a bit puzzled by it. Why does Henry say ”the love of a hyacinth may be rather domestic”? . I thought it was a wild flower?

No doubt, there isn't a flower that evolved in houses. If you look into Ellen Moody's excellent calendar (at JaneInfo), or indeed, in JA's text, you'll see that the talk takes place in "the leafless month of March". Hyacinth, like many bulbous plants, could be potted and induced to flower out of its biological time - which is not the case with a rose bush.