A Journal exploring the value of plants and flowers
25-10-2017 Dr Green

Doctor, is the sun burning my plants?

Words by Dr Green

Photos by Jaap Scheeren

Dear Doctor Green,

I live in a studio apartment on the top floor of a fairly old apartment building with a flat roof. It has big, floor to ceiling south-facing windows. It’s a beautiful space, but, as you can imagine, it gets scorching hot here when the sun’s out. I wouldn’t be bothered by this usually, but I recently bought a few houseplants to brighten up the place and it seems to be affecting them. Some of them are starting to grow brown edges on their leaves. Could my houseplants be getting sunburned?

Kate

Hi Kate,

The short answer to your question is: no. Unlike us humans, plants cannot get sunburned, no matter how much time they spend at the beach. However, it does sound like your plants are getting overheated.

Plants need sunlight to make their food and to grow, and luckily Mother Nature has given plants the unique ability to create their own sunscreen. A 2014 study conducted at Purdue University and published in the Journal of the American Chemical Society found that plants produce molecules called sinapate esters, which are sent to the outer layer of the leaves to protect the plant from ultraviolet-B radiation, preventing it from penetrating to where it might harm the plant’s growth.

However, most houseplants aren’t used to direct exposure to sunlight. Even tropical plants prefer to stay out of the sun in the summer and like a steady temperature around 15-24 degrees Celsius.

I know it is tempting, but covering your plant in sunscreen doesn't actually help.

If your plants’ leaves are turning brown, they are most likely uncomfortable with the heat in your apartment. It is best to move your plants away from south-facing windows during summer months. When they have recovered from their sunstroke you can ‘train’ your plants to start producing their own sunblock by placing them outside in direct sunlight for an hour a day. If their leaves are still getting discoloured, your plants are trying to tell you something. Return them indoors, and help them get their daily dose of humidity by lightly misting their leaves with a sprayer. You must ensure they are out of direct sunlight when you do this. Having excessively damp leaves in the heat of a summer’s day can be very upsetting for your plants.

Good luck!

Are you seeking answers to your plant problems? Ask the Doctor:

drgreen@letitgrow.org

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