Advanced Plant Care: Understanding Sun Stress
Image by @janshalaman
They say that people show their true colours under stress. And this is also true for some plants. Let's talk all about sun stress and how to achieve that gorgeous glow. Have you ever seen photos of the bright reds, purples, pinks, and yellows on succulents and thought it must be photoshopped? Oftentimes, that is the plant's real colour that has come through thanks to sun-stressing.
What causes the red pigments?
Inside the plant cells is a pigment called anthocyanin. It is inactive while the plant is growing under optimal conditions. But it activates in extreme conditions. Much like melanin in human skin cells, anthocyanins act to protect the leaf tissue from UV damage. And just like when your skin when you've spent a day at the beach without sunscreen, the plant blushes those incredible red colours.
How to achieve the colours?
If you guessed that the easiest way to get sun stress is from the sun, you'd be correct! Sun stressing works best on succulents, euphorbias, cacti, hoyas, carnivorous plants, and even some orchids. These are generally plants that evolved to withstand direct sun in extreme conditions. You will have most success with plants that you put outside during the summer, although anthocyanin can activate under strong grow lights too.
Remember that when transitioning your plants outside that you need to start them off in bright shade for 4 - 7 days first. Shade outdoors is typically still higher light that bright light in our homes. After that first week in bright shade you can begin to move them into full morning sun for about 4 hours a day for a few more days before finally transitioning them into full sun. You will likely see colours on your plant come through after a week or so. Expect the most colour to show up in new growth and along the edges and tips of the leaves.
Plants outdoor typically need more frequent watering because sun, heat, and wind can cause water to evaporate faster than inside our home. But remember that most cacti and succulents are drought survival specialists. And the added stress of drying out can even help further the colouration.
As summer fades into fall and temperatures dip at night, expect strong colours to come through. Temperature is another great stressor to cause blushing. Just remember to bring your plants in when nighttime temperatures drop below 7 to 10°C.
Is this good for plants?
Sun stressing is an evolutionary adaptation to surviving extreme conditions. Plants that exhibit sun stressing have evolved the ability to do so in order to withstand relentless direct sun, temperature fluctuations and drought. It will not harm your plant. If you prefer to keep your plants green, they will not sun stress when given optimal conditions because the stressors will not be there.That being said, it is important to know the difference between sun stressing and a sun burn.
Symptoms of Too Much Sun
• Color: Pigments will look washed out and bleached.
• Burns: Leaves eventually get blotchy burns in white, yellow, or brown.
• Texture: Over-exposure is often accompanied by wrinkled, scaly, or crispy leaves.
Remember that sun stressing is best done on types of plants that have evolved to withstand direct sun. Your sensitive ferns and philodendrons will simply burn in full sun. Like all stress, it cannot last forever. Just like with our own skin, that fabulous summer tan will eventually fade. You will notice that when you bring your plant back indoors for the winter that they will fade back to green, counting down the days to when they can go back outside.