Several spice and herbal gardens operate along the roads between Kandy and Peradeniya, offering guided tours of their plantations. The tours walk you through living specimens of cinnamon, cardamom, pepper, cloves, nutmeg, vanilla, and dozens of Ayurvedic medicinal herbs, with explanations of how each is harvested and used. The gardens are commercially motivated — the tours end at a shop — but the educational content is genuinely interesting.
The Peradeniya Spice Garden and Ranawana Herbal Garden are among the better known. Entry is typically free with the expectation that you'll buy something, and the guides are knowledgeable. Allow an hour to ninety minutes.