disclaimer: I don't own the products or services related to HP and JK Rowling, this is merely an exercise in creativity
author's note: another interesting relationship – certainly not romantic, I think Sprout is too sensible for that, but I think they would have worked well together.
summary: she's the first to greet him : "I need some help in the greenhouse"/on trust and smudged-noses/sproutxsnape
He remembers the event distinctly.
He was in his rooms, sorting through his potions journals when a knock came to the door.
She was standing there with a smile and a potted plant in her hands, the clay pot secured in its coverings with a practical length of twine.
"Welcome," she said. "I'm Pomona."
(even when he was headmaster and she did not look at him anymore, he still tended to her plant with great care; his matricaria recutita used for many cups of tea when his nerves frayed)
"If you have some time to spare tomorrow, I'm in need of an extra pair of hands in the greenhouses. Then we can go over what sort of set up you'd like for fresh ingredients for Potions and for your own private stores."
(not once when he sneered or snarled did she bite back, only a warm smile and dug-in heels; a merry wave in the staff room; a tearful thank you when he rescues on of her ill students)
"Yes," he remembers replying. "I will help you."
...
As a child he'd been a bit raggedly dressed, but always clean. Pomona laughs at the smudges on her face.
"It's just dirt dear," she says fondly and pats his hand. "Cleans up just fine."