I was recently reminded of how I learned in middle school that plants could feel. As I recall, some sort of receptors were attached to trees and those trees were then attacked in some way, perhaps being chopped down with an axe. There was some sort of visual representation every time the tree was attacked: I vaguely remember a graph going suddenly from zero to high.
This question is still being asked. Rsearchers at the Institute for Applied Physics at the University of Bonn in Germany found that plants release gases which they said are the equivalent of crying out in pain. They said that what we most closely associate with freshly cut grass, the smell, is really a chemical distress call, and by using a laser-powered microphone they were able to pick up sound waves produced by plants releases the gas ethylene when they were cut or injured.
In 2017, BBC.com published: “Plants can see, hear and smell — and respond.” It questioned not just whether plants have feelings, but instead why and how a plant senses its surroundings has been the study of several Plant Sciences divisions at universities. Jack C. Schulz, at the University of Missouri in Columbia, has spent 40 years researching just this. He points out that, like animals, plants fight for territory, search for food, evade predators and trap prey. Plants even react to recordings of the munching sounds made by caterpillars. They are trying to find what part or parts of a plant respond to sound, and that most likely candidates are mechanoreceptor proteins found in plant cells.
An article — “Do trees have feelings too? One expert says they do” — by Peter Wohlleben describes his career, beginning as a forester in Germany, transitioning to organizing survival training and log-cabin tours. As he guided visitors, he noticed gnarled trees that he would have ignore as a forester. Individually, trees are at the mercy of weather; as an ecosystem, a grove of trees is able to moderate extreme heat and cold, store water and generate humidity, enabling the trees to live to be very old. But the community must remain intact.
These are a few examples of a growing body of research on plant intelligence.  While I believe there is proof that plants do react to various stimuli, I’m personally not sure I can believe a plant has intelligence. Perhaps when the Ents actually start walking I will. — Lloyd Chesley