Plants do communicate with each other, via a fungus network on their roots. They use chemicals rather than sounds or sight to get the message across.

Clever experiment:

The team concerned themselves with aphids, tiny insects that feed on and damage plants.

Many plants have a chemical armoury that they deploy when aphids attack, with chemicals that both repel the aphids and attract parasitic wasps that are aphids' natural predators.

The team grew sets of five broad bean plants, allowing three in each group to develop mycorrhizal networks, and preventing the networks' growth in the other two.

To prevent any through-the-air chemical communication, the plants were covered with bags.

As the researchers allowed single plants in the sets to be infested with aphids, they found that if the infested plant was connected to another by the mycorrhizae, the un-infested plant began to mount its chemical defence.

Those unconnected by the networks appeared not to receive the signal of attack, and showed no chemical response.

"Mycorrhizal fungi need to get [products of photosynthesis] from the plant, and they have to do something for the plant," explained John Pickett of Rothamsted Research.

http://www.ted.com/talks/paul_stamets_on_6_ways_mushrooms_can_save_the_world

OMG is that true?

Well I'm no mycologist at all, all I can do with them is a soup.

I think ted speakers are trustworthy, aren't they?

I think so. His 6 ways mushrooms can save the world TED Talk is from 2008...

...but he had a TEDMED talk in 2011, too.

More:

http://pandawhale.com/post/53567/plants-talk-to-each-other-using-an-internet-of-fungus

http://pandawhale.com/post/31532/trees-communicate-with-one-another-connected-by-fungi