Along Came Tess - Diamonds of London, #6

Life can either snake around you with a strangle hold or produce the most exquisite flowers. At the advanced age of six and thirty, Mr. Jameson Ridley has become content with what he wants out of life. After spending years in India studying the care and cultivation of tea, he became a botanist who specializes in flowers and vines. When he's invited to his best friend's estate in the Irish countryside, he accepts with alacrity, for the opportunity to catalogue the flora there can't be missed. Along comes Lady Tess Cosgrove.
She's the younger sister of his best friend, and she has the power to send his world tip over tail in every way imaginable. if she weren't so maddening. Though she was a Diamond of the First Water during her Come Out year, fate has disappointed her so much that she's given up on London and the ton. As a result, she wants to garden for the rest of her life, to teach others how freeing it is to learn herbal knowledge even though such work is frowned upon in society. Immediately, the unlikely pair butt heads, for they both think their knowledge in horticulture is superior, but when the desire crackling between them ignites into hot passion one summer evening, bigger issues as well as secrets come to light.
If they're willing to spend time untangling roots and unearthing what they want most, love might bloom, but only if it's tended to properly. .and if all else fails, a little summer sunshine, fresh air, and a proper kiss never hurts.