For bonus, the original intended use case of the plant: he watches the gardener go and sends Rapunzel his mostly-wordless assessments of what the man thinks of them - looks like there are no untoward suspicions going on, although he does seem to think they're both very cute, and that whatever Rolan is thinking at her must be terribly hilarious.
Are they just going to sit here in this garden with him loving her and her being pleased about it until it is next time to eat? He thinks that might end up happening.
He loves her. He loves making her this happy. She's so lovely when she smiles. He wants to keep seeing her smile forever.
He carefully disentangles the plant from its perch so he can sit down next to her and hug her and not have to stop being lovey at her while he does this.
Her guards scooch a little closer, but not oppressively so.
(The part of him that's always keeping half an eye out for trouble notes the movement of the guards, but they don't seem to want to interfere, so he supposes it's fine if they report back to Rapunzel's father that the princess and her Ambiguously Close Friend were giggle-hugging in the garden. Although it might lead to Cearl questioning him about his motives again. Eh, he'll deal.)
"I'm sure the plant wouldn't mind, if it had feelings." He pets the plant.
"Probably not. I suppose it makes some sense that most people wouldn't know how to figure out plants, I guess. I count as a plant for this purpose so I could hardly have failed to tell."
...He speculates upon the circumstances under which one might discover Rapunzel's planty qualities, realizes that he doesn't know what level of detail she might be comfortable with receiving of his Things-related thoughts, and drops the full send. But keeps up just the love part.
"I assume you'd notice if you kissed me. Or, I don't know, licked my ear or something, you don't have to taste plants very thoroughly to get what they tell you."