In 500 years we've gone from signalling towers to lasers, fiber and RF. If someone got a 10,000 year jump on us and has a technological improvement rate close to us, we don't know the scale, frequency, or means of communication. There's a lot of physics we know, but there's also more we don't know.

Also, I can't use language bi directionally with a plant no matter how hard I try. Maybe we're the plants. Maybe they don't have language.