The field of horticultural therapy studies the effects plants have on people. This includes everything from enhancing mood by having a single plant in a room to a recent study by British researchers who found that good bacteria in soil may affect the brain in ways similar to antidepressants.
Dr. Richard Mattson, professor of horticultural therapy at Kansas State University, said scientific advances have allowed researchers to measure the body's response to stimuli and pinpoint what happens when people are exposed to plants.
"We're finding that there are changes that happen when we are in the presence of plants," he said. "The brain is working, the autonomic nervous system is involved. We're also finding that some of these changes are affecting our immune system."
One study found that within 40 minutes of gardening, there were changes in the chemicals in saliva that affect the immune system, Mattson said. Another study measured blood pressure and heart rate as people entered and then left a botanical garden. Both rates decreased, which was especially notable given they walked through the garden, an exercise that normally would have increased blood pressure and heart rate.
"I think the evidence is pretty strong that healthwise, there are changes affecting our perception of the environment, the way our minds looks at objects, affecting our sensory system - these are translated into things that make us healthier," Mattson said.
