Disclaimer: The setting and canon characters are J. K. Rowling's; I'm simply lending them for a while.
Pomona loves the feel of soil between her fingers. Loves the way the different types crumble or stick or smooth as she presses handfuls between digits and palm; loves the way she can tell how the ground will affect her plants just by touch alone. Aconite, for example, is most effective when the ground is chalky and dry, slightly tacky to the touch with a tendency to form little balls and suck all the moisture out of her hands. The fossils that the Muggles say form the chalk, so tiny you can't even see them normally, add the potency in some way that's defied the explanations of Potioneers for centuries. Pomona has her own hypothesis, about the gift of death from all those billions of creatures concentrated into a single plant, but isn't ready to tell anybody just yet.
Herbology was never her first love, she came about it in a roundabout route that most Muggle-borns do when they find out that many subjects don't translate well between the two societies. Her first memory is of finding coal in her back garden while she helped her mother plant daffodils; she still has some of the brittle black rock sitting on her windowsill in her rooms, the last of a collection she disposed of when she left Hogwarts with a new speciality and a new love. She found out that some rocks have a different meaning here; capabilities that no scientist could ever have guessed at, and will likely ever know about. Opals, for example, are iridescent semi-precious stones made up of hydrous silica. They also are very good at hiding curses in their flashes of colour and are considered somewhat Dark materials. She found this out when the Defence Against the Dark Arts teacher took her bracelet off her in class with a frown and again quite recently when the Gryffindor girl was hurt with a piece of Victorian jewellery.
Even now she has the bright coloured map of Britain on the wall of the classroom she very rarely uses. The stripes and spots soothing as she traces the boundary lines between ages and epochs and eras underneath her fingers. There's a pin where the castle is, or as close as she can figure out, and it comforts her to know what lies beneath her feet, down through the soil, through the rock, through the layers until she hits the place where even the Muggles aren't quite sure what's there. She likes it that you can know exactly what's under your feet, that makes you stable as you walk along in life. The hill she could see from her old home, for example, was Wenlock Limestone with fossils in it that are 425 million years old. It also, when ground up and included in the fertiliser she uses in the greenhouses, improves the growth rate of Rapaxis capessii ten-fold. She thinks this is because the Tentacular is distantly related to some of the creatures in it but taxonomy is a difficult subject at the best of times and she could be wrong.
There are mysteries that remain though; defying all attempts at logical description and scientific method, and this, this is what the magical world is about to her – why she loves it. That there can still be surprise left in this world despite everyone's attempts to categorise it. Hogwarts castle, for example, is made of stone. An igneous rock with large crystals of quartz, feldspar and biotite. Granite, for all intents and purposes. However, there are other things in there too; flecks of blue and red and gold and green that she can't identify. The blocks are all different temperatures too and remain so through winter and summer (she has a notebook full of figures when she spent a week one Christmas holiday and another that summer cataloguing individual stones and how warm they were). Hogwarts granite is unique in the whole world in its composition and Pomona finds this fits so poetically with how things should be.
She sometimes wonders how things might have turned out differently if she'd declined her letter and gone to the school her father wanted and followed her first love instead of her late-coming second. But, as she looks at the books on her shelf, for example, and sees the pedology textbooks amongst her herbals she thinks that perhaps things aren't so different after all.
Notes: This was written as a response to a challenge on Livejournal's 30minutefics. It was to pick a book at random off your shelves and take the title as inspiration. Try it; it's fantastically fun.