Watering plants lowers blood pressure and anxiety in older adults

Watering indoor plants for just 10 minutes can lower blood pressure and boost feelings of relaxation in older adults. A recent trial compared this simple gardening task to playing a computer card game and found that tending to plants provided measurable physical and mental health benefits. The research was published in the Hong Kong Journal of Occupational Therapy.

As people age, maintaining mental and physical health often requires engaging in structured leisure activities. Occupational therapists frequently recommend non-pharmacological interventions to help older adults manage stress and preserve their motor skills. One popular approach is horticultural therapy, a practice that incorporates gardening tasks to promote holistic well-being. Interacting with plants provides sensory stimulation and offers a gentle form of physical exercise.

Past research has linked gardening to improved self-esteem, better hand coordination, and reduced feelings of isolation in older populations. To measure these benefits, scientists have traditionally relied on self-reported surveys or basic physical metrics like heart rate monitors. Recent advances in wearable technology now allow researchers to directly monitor electrical brain activity during these tasks.

Researchers Li Xiaoyi of the Henan Institute of Science and Technology and Ahmad Hassan of Tongji University wanted to observe exactly how the brain and body respond to a brief gardening exercise. Working with colleagues Jiang Tao and Zhang Deshun, they designed an experiment to compare plant care with a digital leisure activity. They hypothesized that interacting with live plants would yield unique physiological benefits.

The researchers recruited 100 older women living in a nursing care facility in Shanghai, China. The participants had an average age of 68 and were in good physical health with no cognitive impairments. The experiment took place in a quiet, temperature-controlled room to minimize outside distractions and maintain a consistent environment.

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The team set up a crossover trial, an experimental design where all participants eventually complete both activities being tested. On the first day, half of the women spent 10 minutes watering 15 small indoor potted plants by hand. The other half spent 10 minutes playing a digital game of Klondike Solitaire on a computer. The following day, the two groups switched tasks.

Before and after each session, the researchers measured the participants’ blood pressure using a standard blood pressure cuff. They also utilized an electroencephalogram, commonly known as an EEG, to continuously record brain activity. Participants wore a specialized headband equipped with dry sensors that rest on the forehead. These sensors detect the faint electrical signals produced by brain cells communicating with one another.

The headset specifically monitored the frontal lobe, a brain region heavily involved in attention, memory, and emotional regulation. The researchers focused their analysis on two distinct types of brain frequencies: alpha waves and beta waves. Alpha waves are relatively slow electrical patterns that typically appear when a person is in a relaxed, peaceful state. Beta waves are faster and generally emerge when a person is actively concentrating, alert, or anxious.

Alongside the physical sensors, the participants completed two standardized questionnaires to assess their subjective emotional states. One survey measured their current anxiety levels using a numerical scale. The other asked them to rate their immediate feelings between opposing concepts, such as feeling comfortable versus uncomfortable.

The physiological data revealed distinct physical responses to the two activities. Watering the indoor plants prompted immediate drops in both systolic and diastolic blood pressure. Systolic pressure measures the force of blood against artery walls during a heartbeat, while diastolic pressure measures the resting force between beats. A reduction in both metrics indicates a calming effect on the autonomic nervous system, which controls involuntary bodily functions.

Playing the computer game did not produce these relaxing physical changes. The heart rate of the participants remained relatively stable across both activities, showing no statistical difference in pulse. The most notable differences emerged in the electrical activity of the brain.

During the first few minutes of the plant-watering task, the women experienced a surge in alpha wave activity. This initial spike suggests that interacting with the plants fostered immediate mental relaxation. During the same period, their high beta wave activity also increased, pointing to a state of heightened attentiveness.

Experiencing both increased alpha and beta waves suggests the participants were in a state of alert relaxation. They were calm but fully engaged with the task of watering the plants. In contrast, the women who played the computer game showed decreased alpha and beta activity. This opposing brainwave pattern is often associated with mental fatigue, boredom, or stress.

Across the entire 10-minute session, the overall increase in alpha waves for the gardening group was not statistically significant. However, the overall beta wave increase remained substantial for the duration of the task. The EEG headsets also calculated a proprietary meditation score, which rose notably during the plant-watering task compared to the computer game.

The subjective survey results mirrored the objective physical measurements. After tending to the plants, participants reported lower overall anxiety scores on their questionnaires. They also rated themselves as feeling much more comfortable, natural, and relaxed than they did after playing the computer game.

While the results highlight the potential benefits of brief interactions with nature, the study design has limitations. The experiment only tested a single 10-minute session using one specific type of indoor potted plant. The effects of longer gardening sessions, different types of plants, or outdoor environments remain unknown.

The demographic makeup of the study was also highly specific, focusing entirely on a single group. All participants were older women living in one nursing facility in China. The psychological and physical responses to gardening might differ across different age groups, genders, and cultural backgrounds. Future trials involving diverse populations would help clarify how broadly these benefits apply to the general public.

The study, “Psychological and physiological benefits of horticultural therapy for Chinese older adults,” was authored by Li Xiaoyi, Ahmad Hassan, Jiang Tao, and Zhang Deshun.