If your windowsills are anything like mine, they are filled with the first batches of seeds for the coming year. The problem is that seedlings grown in the coziness of a large room are notoriously prone to growing long and leggy and often collapse within just a few weeks of germination. But can old-school colorful techniques help keep our gardening hopes alive in 2026? Here's the science behind why petting plants isn't as crazy as it sounds.
Plant propagation is often a balancing act. Growing tender seedlings under glass, away from extreme temperatures, harsh winds and the constant threat of pests and diseases greatly improves their early survival. However, the absence of environmental stress can have unintended consequences. Etiolation—when plants grow tall but fragile—is a common problem for houseplants, including in commercial nurseries. Once exposed to the open air, these specimens are much more likely to physically break down. With billions of dollars at stake around the world, it is not surprising that commercial producers spent decades searching for efficient, scalable solutions.
Chemical growth regulators are one answer to help create stronger, more compact plants. However, many of these substances are not available to home gardeners. Fortunately, research has shown that mechanical stimulation—simply rubbing, shaking, or stroking the seedlings—is also extremely effective in reducing etiolation. It's all about a phenomenon called thigmomorphogenesiswhen plants change their growth patterns in response to forces such as touch, wind, rain or vibration, by growing thicker stemsmore supporting tissue and an overall shorter, stockier stature. Although scientists still do not understand exactly how plants perceive and translate these signals at the cellular level. numerous studies demonstrate that mechanically stimulated seedlings are not only structurally stronger, but also more resistant to threats such as pests and drought.
This has been demonstrated in a range of popular garden species, from tomatoes and lettuce to petunias and marigolds. Experiments using fans, vibrating tables, or even a sheet of paper passed over foliage have shown that these measures can reduce excessive stem elongation by 20 to 50 percent.
But here's the best part: Although commercial manufacturers have been using machines to create this kind of physical stimulus since the 1970s, it's easy to replicate at home. Tests have shown that to achieve the effect, it is enough to gently stroke the seedlings only 10 times, just once a day. You can do this with an old envelope, a soft feather broom, or even your hands. That's a pretty good payoff for the 10 seconds a day it takes, and it's all backed by solid science.
These articles are published every week on the website
newscientist.com/maker
James Wong botanist and science writer with a special interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew in London, he shares his tiny apartment with more than 500 houseplants. You can follow him on X and Instagram @botanygeek.
