According to Swiss researchers Mousavi and Chauvin, the nervous system of animals are capable of sending electrical signals at speeds up to 100 meter per second. Plants do this at speeds up to 3 meter per second.
This means that a tree in the Netherlands can send a message throughout the country in less than 2 hours and a tree in the south of Germany can send a message in a bit more then one day throughout Europe. If a tree in Paris, France would want to send a message to a tree in Shanghai, China, then this would take about 4 days.
The question, what plants are talking about under our feed, is still a mystery.