Do Houseplants Reduce Stress?

Are you stressed? You should grow houseplants! Just ask all the experts. Try an online search and you’ll come up with almost two million sites claiming that growing plants reduces stress. Even the National Institute of Health has jumped on the bandwagon with a study “proving” that houseplants reduce both physical and psychological stress, at least in young men.

Unlike the articles that tout huge benefits in air quality from including plants (especially spider plants) in your home (NASA said it so it must be true—but see my post here), there may actually be some basis for the stress-reduction theories. Or not.

The NIH study went as follows: Two dozen male grad students were split into two groups. One group worked at a computer task—a document in a word processor. The other transplanted some potted plants. Their blood pressure, heart rate, and a questionnaire about feelings provided data. Because the students “felt more comfortable, relaxed, and natural” and had lower blood pressure when they were transplanting, compared to when they were word processing, the study concluded that plants reduce stress.

I have a lot of reservations about this study. For one thing, many people find computers pretty aggravating, even those young enough to be “digital natives.” It doesn’t say which word processor they’re using, but there’s not much competition out there. I bet it’s Microsoft Word. Personally, I find Word very frustrating. It’s not intuitive. Even though I’ve used it for years (to write all these posts, for one thing) and I’m very familiar with it, I still spend a significant amount of time fighting with its auto-assumptions. Before I discovered how to make it dumber—so it doesn’t try to outguess my intentions—I’m sure that using it raised my heart rate and blood pressure! No surprise here.

It’s also not surprising that working with a plant resulted in more “natural” and “relaxed” feelings than working with a computer. Plants are natural. Computers are not. Plants don’t try to outsmart you. And it requires significantly less concentration to repot a houseplant than to format a document.

I’m not at all sure how this study concludes that plants reduce stress. They could just as easily concluded that computers raise stress levels!

What about other evidence supporting the idea that houseplants reduce stress? A study in the Netherlands placed plants in hospital rooms and determined that they reduced patient stress.

However… this conclusion points out a very common, major flaw in experimental design. All these studies compare stress levels between “plants” and “no plants.” But is it the presence of plants that causes reduced stress? In this hospital study, the researchers believe that the effect was due to the increased “perceived attractiveness” of the room. Would nicer drapes would have worked as well?

Perhaps stress levels are lower because we’re caring for something living. Think of the studies that associate owning a pet with increased happiness and a longer, healthier life. Or maybe plants are simply a welcome distraction from the boredom (and often, pain) that hospital patients experience.

In fact, a thought-provoking study reported in HortScience found no statistically significant benefit to having plants in an office setting. In fact—

Only one of the correlations involving plants is statistically significant; the greater the number of plants placed within 1 m from the respondent’s desk (plants nearby), the higher the level of perceived stress.

Owning lots of houseplants doesn’t always reduce stress. Pete and I downsized a couple of years ago. The house we sold had passive solar heating—the entire south wall was windows—and of course I filled the space with houseplants. Our new house is more traditional and significantly smaller. All my beloved plants would simply not fit, so I found most of them new homes.

Until we moved, I hadn’t realized how much time I had been spending tending to my indoor jungle. Watering took several hours a week, and often made a mess that needed mopping up. Pinching, pruning, turning, repotting (another messy job), and moving them around each time I washed the tile floor—more time. Worst of all, houseplants get bugs. I can assure you that seeing mealybugs on my plumeria for the zillionth time does not result in lower blood pressure.

Whether or not to own houseplants is a personal decision. Left to his own devices, my husband wouldn’t bother. He’s focused on other activities, and he’d forget to water them. Their care would simply be another chore he’d rather forego. On the other hand, I love to garden and houseplants allow me to continue to do so during our long, cold winters. Besides, I think they look nice. We have houseplants because I like them. That’s a good enough reason.

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