Did you know that there are plants that predict the weather? Dandelions and these five other plants can tell you when it may rain, the temperature outside, and more!
Despite their reputation as pesky lawn weeds, dandelions are also good indicators of rain—especially since you’re likely to find them wherever you go! Like pimpernels (see below), these herb-flowers close when they detect moisture and reopen when the weather dries. Learn more about dandelions.
The scarlet pimpernel is such a good prognosticator of fair and foul weather that it has been nicknamed the “poor man’s weather glass.” Its blooms remain open in full sun, but when skies turn cloudy or humidity reaches about 80%, they fold up like little rain-shy umbrellas. They do this to keep their pollen dry and their nectar from being diluted.
Even fallen pine cones can be used to predict the weather. If the air is dry, pine cones fan out their scales, resembling mini-Christmas trees. If, however, there is a rise in humidity or if rain is in the air, their scales will clamp tightly shut, overlapping one another. This finicky behavior has to do with seed dispersal phenology.
During dry weather, seeds nestled deep within the pine cone are looser, lighter, and more easily carried off by winds. But when the weather is damp, seeds are prone to clumping together and won’t travel as far away from home.
Contrary to dandelions and other plant prognosticators, earthstar (Astraeus hygrometricus) is observed during gloomy weather and predicts when conditions will clear. This fungus—which resembles a brown mushroom surrounded by a skirt of leathery “petals”—remains open during rainstorms (raindrops help disperse its spores), so when these “petals” curl up and enclose the center spore sac, you can expect rain to end soon. Learn more about Earthstars and other fungi at the NationalParkService.gov.
If you’re a coastal dweller, be sure to keep an eye on any surfaced seaweed. Pay particular attention to what this humidity-sensitive plant does after it washes ashore and lies exposed to the air. When it plumps up, that’s an indicator the weather is damp and muggy. (This is likely a result of the plant being coated with sea salt, which is hygroscopic and attracts moisture.)
If, however, surfaced seaweed appears shriveled and dehydrated, take it as a sign that conditions are dry.
Curious to know the current air temperature? Look to the nearest rhododendron shrub. When temperatures dip to 32 degrees Fahrenheit (freezing), a rhododendron’s long, leathery leaves begin to droop and gradually curl inward. And at 20 degrees and lower, their leaves are tightly curled, like cigars, and point straight down to the ground.
This behavior is basically a defense mechanism. Since rhododendron plants aren’t able to soak up as much groundwater when soil is frozen, they curl their leaves so as not to lose water through them. However, once temperatures creep back above the freezing mark, rhododendron leaves fully unfurl and return to their flat, oval shape.
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Tiffany Means is a freelance writer and a degreed meteorologist. She specializes in weather forecasting and enjoys making the subject of weather (and the science behind it) more relatable. She currently resides in the Blue Ridge Mountains of North Carolina.