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Watering your garden in the midday sun can burn plants

Scientists have finally confirmed what gardeners have long claimed: Water droplets can burn certain plants at the wrong time of day.

By Bryan NelsonTue, Jan 12 2010 at 7:18 AM EST

BURNT BOTANY: Plants with hairy leaves are particularly at risk. (Photo: KatyaPalladina/Flickr)
It's part of the entrenched mythology of the gardening world: if you water your plants in the hot midday sun, the droplets can act as a magnifying glass and burn the leaves. But until now, science had been unable to confirm the folklore as fact.
 
"The problem of light focusing by water droplets adhered to plants has never been thoroughly investigated, neither theoretically, nor experimentally", said Dr. Gabor Horvath of Hungary's Eotvos University.
 
Determined to discover the truth, Horvath and his team of researchers conducted a series of computer and experimental studies on the problem, with surprising results. The studies confirmed that plants can be sunburnt from water droplets  — and people can too.
 
The connection lies in the types of plants most susceptible to getting burned. It turns out that water droplets on a smooth surface, such as maple or ginkgo leaves, cannot cause leaf burn. But plants with hairy leaves, such as the small wax hairs of floating ferns, tend to hold water droplets in focus above the leaf surface, magnifying the sunlight. The same principle holds true for water held above hairy human skin after bathing.
 
Researchers also considered if the same process could potentially start a fire if the light-focusing occurred over dried-out vegetation, but their results were mixed. While fires are theoretically possible, there are some natural factors that make them less likely.
 
"The likelihood [of a fire starting] is reduced as the water drops should evaporate before this, so these claims should be treated with a grain of salt," concluded Horvath.
 
Nevertheless, the study was clear about what gardeners and poolside loungers have long known. During times when the sun is most intense, it would be wise to keep yourself and your plants dry.
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anonymous
Rosie James 01/15/2011 17:48 PM

Does watering burn plants?
Question:
Now that hot weather has arrived, people are being urged not to water during the day. The most obvious reason is to reduce evaporation and blow off. Yet, I continue to hear comments that watering during the day will burn your plants. Reasons cited -- water droplets act to magnify solar intensity and that water is the best source for heat conduction (this from a fireman).

Does water really burn the plants? It doesn't seem.... More

anonymous
NJG 01/13/2010 12:09 PM

Thank you for this tip. Honestly, I've mistaken my dog for ruining my garden. Thinking that she has been peeing on some of my plants that's why they all got dried, but after reading this I thought, that could be the reason why. I mean, I have been watering my plants during noon time cuz I have no time in the morning and afternoon. Anyway, thanks again.

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