According to the Rev. Franklin Loehr, prayer could supercharge the growth of plants. Pretty much any prayer would work. He detailed his argument in his 1959 book The Power of Prayer on Plants
When Richard Nixon was told of Loehr's results, he reportedly said, "That sounds like a good kind of thinking to me."
However, in 1961, a group of Harvard students tried to replicate Loehr's results and failed to do so
. In fact, in their experiment the plants that weren't prayed for at all grew better than plants that were prayed for by either skeptics or believers.
More details from Newsweek
(Apr 13, 1959):
Can prayer make plants grow faster and bigger? Skeptics think it laughable, scientists find it irrelevant, and farmers tend to rely on more mundane methods to increase their crops. But the Rev. Franklin Loehr is convinced that the answer is yes, and has just written a book, "The Power of Prayer on Plants," to tell why.
After five years and 900 experiments, the 46-year-old Presbyterian minister reports he and 150 members of his prayer group found that prayed-for wheat and corn seeds grew into bigger seedlings than ones which got no prayer or outright negative prayer. Commenting on their methods last week in his Los Angeles home, Mr. Loehr explained that they used every kin of prayer and found every one effective to a degree.
"There were silent and spoken prayers," he continued, "those to loved ones, and the humble prayer straight to God. But mostly people just talked to the plants, loved them, or scolded them. First I tried buddying up to them, and then I observed that the people getting better results were approaching the plants on their own level of consciousness."
Picking up a copy of the book, he pointed to the jacket, which shows a lone, stunted shoot on the no-prayer side of an experimental seedbed. "He wasn't supposed to be there," explained Mr. Loehr, "so we blighted him with three bursts of negative command."
Mr. Loehr dropped the experiments two years ago, having persuaded himself, at least, of their validity. He is now concentrating on "soul dynamics" prayer for people—not, of course, to make them grow faster and bigger. "The fact is," he concluded, "we used plants to test prayer just as the artificial heart is tested in dogs instead of humans."
Along similar lines, see our previous post "Does holy water help radishes grow better?"