Scientists are stunned about new evidence that plants can distinguish between plants related to it and those that are not. Besides actually recognizing its relatives, the plant gives them preferential treatment.
A study carried out by McMaster University in Hamilton, Ontario, (Biology Letters 2007; 3: 435-8), examined how the Great Lakes sea rocket (Cakile eduntula) reacted with plants of the same species when sharing a pot.
The plants competed with strangers for soil nutrients, but not withkin.  In the presence of strangers, the sea rocket plants aggressively sprouted roots to soak up all available nutrients.  However, with family, the plant restrained itself and settled for more modest root growth.
The Canadian researchers believe that root interactions may provide the key for kin recognition among plants.  Plants work out who is family and who isn’t by checking out each other’s roots.

Constant communication
But in my view, the larger implication is that that plants have a primary awareness of their environment and — in common with every other living creature — are constantly communicating with it.
Or as Susan A. Dudley, an evolutionary plant ecologist, who led the study, puts it: “Plants have a secret social life.”
This is not the first evidence of what Cleve Backster has termed ‘primary perception’. For some 20 years scientists have discovered that plants sense the presence of competing plants through subtle changes in light (certain plants have ‘signature shifts’), or by the release of another plant’s chemicals.  The dodder plant, a parasitic weed, actually very deliberately sprouts toward its potential host plants, making intelligent choices about which plant would enable it to survive the longest.
Backster himself discovered a ‘plant learning curve’ when the famous remote viewer Ingo Swann had come to visit him at his lab in October 1971. Swann wanted to repeat Backster’s initial experiment with his Dracaena, in which the plant reacted, as shown on polygraph equipment, to Backster’s thought of burning one of its leaves.  With Swann’s study, the plant’s polygraph began to spike when Swann imagined burning the plant with a match. He tried it again, and the plant reacted wildly, then stopped.
‘Do you think,’ Swann then said to Backster, ‘that it has learned that I’m not serious about really burning its leaf? So that it now knows it need not be alarmed?’
Swann thought of putting acid in the plant’s pot. The needle on the polygraph again began to zigzag wildly. Eventually, the plant appeared to understand that Swann was not serious. The polygraph tracing flat-lined. Swann was shocked at the thought that plants could learn to differentiate between true and artificial human intent.
Backster’s work, combined with the latest evidence, raise the possibility that plants are have a seething and sensory inner life, with abilities common to animals: sensing, learning, memory, and in the case of the sea rocket, the ability to distinguish friend from foe.
Indeed, some 20 international scientists have created the Society for Plant Neurobiology, and although they do not suggest that a little brain is lurking somewhere inside a plant, they do acknowledge that plants have internal electrical signaling  — much like a primitive brain.
Many people choose vegetarianism because they feel that it is cruel to kill and eat sentient beings.  What if plants are sentient too?
Try the McMaster experiment at home:
Take two seedlings from the same family and plant them in the same pot.  See if they thrive.  Now take two seedlings from different plants and again plant them in the same pot.  See which grows higher.
Or, watch the plants in positive or negative environments.  See which grow higher.