Have you noticed that succulents planted as groundcovers usually have much more vibrant colors than the ones grown indoors with indirect light? That is a very interesting fact about succulents: they become “sun stressed” and develop brilliant bright colors under a lot of direct sunlight and extreme conditions.
Sun stress or any type of environmental stress may be harmless for succulents when it does not reach an over-stressed level. In fact, sun-stressing at the right dose is done a lot to succulents to bring out their gorgeous colors. Too much sun stress, however, would burn your plants. Sun stress, thus, can be both good and bad for succulents. How much you can safely sun stress your plants depends on a lot of things, for example, the climate where you live, the time of the year, other environmental factors surrounding your succulents, and the types of plants you want to stress.
What is Succulent Sun Stress?
Succulents usually develop a response to changes in their ideal growing conditions. This is their evolutionary adaptation to extreme conditions like relentless sunlight, temperature fluctuations, and drought. When sun-stressed, succulents are pushed to a stress level that they must activate a pigment called anthocyanin. Like human melanin, anthocyanins work to protect foliage tissues from UV damage. The result is that we get darker, tanning skin, and succulents bring out their incredible red and yellow colors. Sun stress does not last forever. Just like our tan fades when summer ends, a sun-stressed succulent will fade back to its green color when you bring it indoors, or when the dark winter comes.
Photo by Veronika Gaudet
Sun-stressing is only recommended for plants that can withstand extreme direct sunlight, for example, succulents, cacti, euphorbias, hoyas, and some orchids. You can sun-stress a plant with very strong grow lights, but natural sunlight gives the best result and creates the most well-stressed succulents. The sun-stressing process usually involves reducing temperature and humidity levels, as well as a less frequent watering schedule.
[Is Sun Stress Good or Bad?]Is Sun Stress Good or Bad for Succulents?
Sun stress can be a good thing only if it is done right. Many colorful succulents adapt well and can produce more breathtakingly beautiful colors when exposed to stressful conditions. Most succulents come from arid desert areas with dry soil, extreme heat and plenty of direct sunlight. Sun-stressing mimics their natural habitat, and to a certain extent, it is totally harmless to these plants.
However, sun-stressing can turn very bad and burn or even kill your plants if the sun is too harsh for them to handle. It is very easy to detect that your plants are over-stressed. Well-stressed succulents have normal leaf texture and look healthy, but over-stressed plants have blotchy, darkened, wrinkled, or crispy leaves.
Sun burn succulents
Photo via harddy.com
How to Safely Sun Stress Your Succulents?
We would not recommend sun-stressing for beginners. Succulents are very sensitive to any changes in their environment, and a bit more or less of anything, if not done correctly, would harm your beloved plants.
Not all succulents are the same. Although most succulents can benefit from sun stress, some are easier to sun stress and yield a better result.
Sedums and Crassulas are some of the best plants to work with when you first start your sun-stressing experiment. They are resilient, sun-loving succulents that can quickly develop vibrantly red, yellow, and pink colors when exposed to more sunlight. You can also choose cacti, agave, or jade plants as these species are also easy to sun stress.
It is very important to acclimate your succulents to direct sunlight, especially if they have been indoors and have accustomed to indirect lighting. We recommend that:
- First, bring your plants outside in the morning for a few hours a day. Place your succulents under some shade for about 1 week to provide them with dappled sunlight
- Move them to a partial-sun spot for the following week.
- After that, you can move them to a sunnier place.
Throughout this process, you need to monitor your succulents carefully to detect any sign of sunburn and over-stressed. Move your plants indoors or to a shady place right away if the leaves have darkened burning spots, and your plants overall look unhealthy.
The amount of sunlight may decide how much change in color your succulents develop, so check these changes daily to adjust the amount of sun exposure. Regarding how much sunlight is too much, there is a delicate line between having well-sun-stressed succulents and ending up with over-stressed ones. You need to figure this out for yourself through careful monitoring.
In addition to more intense, direct sunlight, you can help to boost the color of your succulents by giving them a bit more extreme change in their environments.
You should start by reducing watering and placing your succulents in a spot with good air circulation. Along with dry soil, good airflow results in a lower humidity level which is necessary for a successful sun-stressing.
Succulents are also pushed to produce more anthocyanins when exposed to cooler temperatures. The ideal temperature for succulents is between 65-75 degrees Fahrenheit, and if it drops below 60 degrees Fahrenheit (but above 40 degrees Fahrenheit), the foliage colors will start to intensify. This is the reason why outdoor succulents blush the most beautiful colors during the beginning of Autumn or Spring.
Although direct sunlight and outdoor environment work best in producing beautiful sun-stressed succulents, you can also try to sun-stress them with a LED grow light. The success rate may be lower than with natural sunlight, but if you decide to try this method, here are a few suggestions:
- Use only a broad-spectrum LED grow light. Blue light promotes anthocyanin production, but plants also need other light colors to develop certain stress colors.
- For common succulents, for example, Echeveria and Crassula, light intensity to bring out stress colors is 120 – 150 umol/m2/s, which can be achieved with 24W LED grow held at a distance of between 8 and 12 inches from the succulents for 13-18 hours a day
- Make sure your grow light does not emit heat that can burn your succulents
Don’t forget to take care of your succulents during the sun-stressing process:
- Make sure they have well-draining, porous soil
- Avoid extreme temperatures (over 85 degrees Fahrenheit or below 40 degrees Fahrenheit)
- Protect them from insects, pests, and animals when they are placed outdoors
If you want to sun-stress your succulents, you may need to try this method several times. Remember that trials may come with errors and failures, and that is totally normal. If your succulents have sunburn, remove the damaged leaves, and try again with less intense sunlight. If your plant does not transform into a more vibrant coat, you may increase the sunlight exposure and follow our instructions above.