How to Add Stress Colors to Succulents (With LED Light)

Do you know that you can change the color of your succulents by simply giving them some stress such as sun stress?  In fact, many nurseries use this technique to add unique, pretty colors to their plants so as to sell at a higher price. 

Giving your succulent stress does not necessarily mean that you are harming your plant or will cause sunburn.  

And, sun stress is not the only way to make your succulents to change color.

You can safely make your succulents turn pink, red, orange or even blue and purple by giving them prolonged periods of strong light, cool temperature, infertile soil, and drought when they are dormant.

Even though you do not have access to strong natural light, you can put your succulents 12 inches away from 24W LED lights for 14-18 hours.  

To learn more about how to sun stress succulents using grow lights, read on!

1. Why do succulents turn red?

Succulents turn red naturally when it is under stress as a self-defence mechanism to protect themselves from environmental stress, such as strong light, low temperature.  The red color, which can also appear as purple, blue or black, is due to the release of a chemical called anthocyanin. 

Anthocyanin is also commonly found in autumn maple leaves, dark purple pansy flowers, and oxidant-rich fruits and vegetables, such as blackberries, blackcurrants, blueberries, red cabbage, cherries and eggplants, purple corn, black rice, etc. (Lo Piero et al. 2005).

Therefore, the unique colors are in fact “stress colors”.

2. How to sun stress succulents with LED light?

If you cannot give your succulents enough natural sunlight, for example during winter, you can sun-stress your succulents using LED grow lights.  For that, we need to consider light intensity, duration and quality.

2.1 Light Intensity

According to several studies on stressing Echeveria and Crassula, the best light intensity to bring out stress colors is 120 – 150 umol/m2/s.

In the study of Echeveria, it shows that the tips and leaf edges turn deep red or even brown under strong light (120 – 150 umol/m2/s), a little light pink under medium light (75 umol/m2/s) and remain as green under low light (35 umol/m2/s).  Although the succulent showed hints of pink hues under medium light, the most intense colors or the best appearance was achieved under strong light.

Light intensity	Plant color change
Low light (35 umol/m2/s)	Lighter shade of green with no other color
Medium light (75 umol/m2/s)	Light green with hints of pink on leaf edges
Strong light (120 - 150 umol/m2/s)	Bright, vibrant green with intense red on leaf edges

(Source:  Erwin, Altman & Esqueda, 2017; Cabahug, Choi & Nam, 2019)

What does 120 – 150 umol/m2/s mean when it comes to the choice of LED light? 

Grow lights that emit light intensity in this range would be 24W LED light (an equivalent of 800W), held at a distance of between 8 and 12 inches from the succulents. 

(By the way, lumens is not a good measure of how bright the light is for growing plants because it only measures how bright it appears to the human eye. A better indicator is umol/m2/s or wattage.)

You should experiment with different distances and adjust according to the response of the succulents.  If signs of sunburn such as brown spots develop, you should move the grow light further away from the succulents.

2.2 Light duration

According to several studies, it generally takes between 13 up to 18 hours per day to bring out stress colors in your succulents (Nam et al. 2016, Brown, 2018, Trinklein, n.d.). 

Since the optimal duration depends on the type of your succulent and your environment, you should experiment starting with 13 hours per day and slowly increase the duration until you reach the color intensity you like.

2.3 Light quality (color)

The best is to give the succulents a broad spectrum of light, like sunlight, between 400 nm (blue) and 700 nm (red) of wavelength which is crucial for photosynthesis.

Blue light helps promote the production of anthocyanin in plants, resulting in red hues in leaves (Lian, Cha. Moe, Kim, & Bang, 2019).

But plants also require other light colors to achieve certain stress colors.

3.  Best grow light for stressing succulents: Barrina T8

To learn more about the criteria we use to pick the best grow light, check out this article about choosing the best grow light.  The criteria are the same for growing orchids. But briefly, the right grow light for succulents:

• Must emit a full spectrum of light for photosynthesis
• Must emit light intensity (PPFD) that is not too weak to bring out stress colors in succulents
• Does not produce heat

Other factors that are also good to have:

• The light appears white or warm white visually which is easier on the eyes than pink or purple light
• Longevity
• Easy to install
• Light-weighted
• Can daisy chain
• Reasonably priced

Using these criteria, we have found that the Barrina T8 model is the best-value choice, not only for growing orchids indoor, but also for succulents.

For only $59.99, you will have 6 lights which is perfect for a stand with 3 shelves (i.e. 2 lights per shelf).

The best light intensity for bringing stress colors for succulents, which is 120-150 umol/m2/s, can be achieved by placing two of these Barrina T8 lights at a distance of 12 inches from the succulents. They will receive an intensity of light of around (132 x 2) umol/m2/s x 60% = 156 umol/m2/s.  A 40% discount is applied to the light intensity specs given by the manufacturer because the readings were measured in an enclosure that reflects light.

4. Other ways to make succulents turn red

Apart from sun stress, there are three other ways to bring out stress colors in succulents and you can use one of these ways or a combination of them to achieve stress colors.

4.1 Cold/Heat Stress

Whether high or low temperature is considered stress for the succulent depends on the succulent type and their optimal range of temperature.

For succulents that are dormant in winter, e.g. Echeveria, Agave, Seumpervivium, are more sensitive to environmental stress in the winter, e.g. the cold, and thus produce a stress response or more red pigment at low temperature.  A study of Echeveria shows that the succulent produced more of the red-pigmented anthocyanin under low temperature between 50°F (10°C) and 68°F (20°C), but remains green when it was hot at 86°F (30°C).

Summer-dormant succulents, Aloe, Aeonium, Graptoveria, which are more sensitive to environmental stress in the summer, e.g. high temperature, thus produce a stress response or more red pigment at high temperature in the summer.

A list of the summer-dormant and winter-dormant succulents are listed below

4.2  Water Stress

If you water your succulents once a week, that’s far from being stressful for your succulents to produce the red pigment. 

To bring out stress colors in your succulent, water much less frequently:  first try once a month, then maybe once every two months.  Once you decrease the watering frequency, you will notice more colors pumping out.

4.3 Nutrient Stress

The lack of minerals in the soil is also stressful for the plant.  To create a drought situation, it is important to create potting media with good drainage.  A good mix is ½ potting soil, ¼ sand, ¼ perlite.

5. When can I stress my succulents?

You can stress your succulents any time of the year to make them change color.  But, it is recommended to give them stress, e.g. strong light, less water, when they are dormant instead of during the active growth stage, since that will impede their development.  

It is also much easier to achieve a more intense red color when the succulent is dormant, compared to the growing stage when the red pigment starts to fade.

This table shows some of the common succulents that will turn red when they are stressed.

6. Do all succulents change color when stressed?

Not all succulents can change colors under stress, as some will remain green even though they are stressed.  This depends on the pigment available in the plant. 

Examples of succulents that will not change color and remain green despite under stress are Portulacaria Afra ‘Elephant Bush’ and Crassula Tetragona.

If they start to change color, something is wrong with the succulent.

7. Is stress bad for succulents?

Succulents are adapted to living in harsh environments that are uninhabited by other plants, such as arid areas, dessert, mountainous areas, cliffs, sea coast.  So, when they are under stress, it is mimicking their natural habitat.

Moderate stress does not mean we are killing the plant.  Stress only means that the plant is under conditions that are not optimal, such as having less water, prolonged sun exposure.  

Moderate sun stress does not result in sunburn. 

However, watch out when your succulent has intense red or brown colored leaves, over-doing it can also lead to sunburn.

Check for signs of sunburn, i.e. dry, white patches, and sometimes brown or black secondary infection areas. 

Afterall, sun-stressing using LED lights is safer than exposing your succulents under direct sunlight as you can control the intensity by adjusting the distance between the plant and the light as well as restricting the duration of light. 

Conclusion

“Stress” is not always bad for our plants and a moderate dose will not cause sunburn.  

Instead, this can be used as a technique to bring out unique colors of red, orange, blue, purple in your succulent’s leaves by putting them in conditions that are not usually optimal, such as prolonged and strong light, extreme temperature, drought and infertile soil. 

The key to a safe application of this technique is to do so only when they are dormant.

Happy growing!

References

1. Brown. D. (2018) Cacti and Succulents. University of Minnesota.
2. Cabahug, R., Soh, S.Y., & Nam, S.Y. (2017a). Effects of Light Intensity on the Growth and Anthocyanin of Echeveria agavoides and E. marcus. Flower Res. J., 25(4). 262-269.
3. Cabahug, R., Soh, S.Y., & Nam, S.Y. (2017b). Effects of Shading on the Growth, Development, and Anthocyanin Content of Echeveria agavoides and E. marcus. Flower Res. J., 25(4). 270-277.
4. Cabahug, R., Choi, Y.J., and Nam, S.Y. (2019). Effects of Temperature on the Growth and Anthocyanin Content of Echeveria agavoides and E. marcus. Flower Res. J. 27(2), pp 80-90.
5. Egri, Á., Horváth, Á., Kriska, G. and Horváth, G. (2010). Optics of sunlit water drops on leaves: conditions under which sunburn is possible. New Phytologist, 185: 979-987.
6. Erwin, J., Altman, K., & Esqueda, F. (2017). Temperature Impacts Cactus and Succulent Development Rate. HortTechnology. 27(1), pp 65-68.
7. Hart, C. (2017, December 15). Growing Succulents: Beyond The Basics. Illinois University Extension.
8. Ma, Y., Li., X., Gu, Z., & Li, J. (2019). Leaf Color and Growth Change of Sedum rubrotinctum Caused by Two Commercial Chemical Products. HORTSCIENCE. 54(3).. 434–444.
9. Nam, S.Y., Lee, H.S., Soh, S.Y., & Cabahug, R. (2016) Effects of Supplementary Lighting Intensity and Duration on Hydroponically Grown Crassulaceae Species.Flower Res. J., 24(1).
10. Li, T.C., Lin, T.C., Martin, C.E. (2015). Leaf anthocyanin, photosynthetic light-use efficiency, and ecophysiology of the South African succulentAnacampserosrufescens(Anacampserotaceae). South African Journal of Botany. 99, 122-128.
11. Lian, T.T., Cha, S.Y, Moe, M.M., Kim, Y.J. & Bang, K.S. (2019). Effects of Different Colored LEDs on the Enhancement of Biologically Active Ingredients in Callus Cultures of Gynura procumbens (Lour.) Merr. Molecules, 24(23).
12. Shaw, J. (2018) LED Colour Temperature and its Effect on the Growth of Hydroponic Lettuce Seedlings. The Young Researcher, 2(1), 164-173.
13. Trinklein, D. (n.d.) Lighting Indoor Houseplants. University of Missouri Extension.

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Carol Chung

Editor and Founder at AskGardening

Carol is a journalist, teacher, and plant lover. Over the past 20+ years, she has nurtured countless potted plants and orchids in small indoor spaces. Her expertise also extends to growing natural, organic vegetables in farms in South America. Passionate about sharing her knowledge, she writes to help others to create their beautiful gardens. Discover more about Carol.

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