Succulent Stress / Colour

What is Succulent Stress?

When succulents are exposed to certain conditions, they become “stressed.” Stressing succulents in the right way can bring out their best colour and appearance. The factors that can stress a succulent are light (and UV radiation), temperature, and drought (lack of water). The key to stressing succulents well is is to induce a certain amount of “stress” without overdoing it. Growing with a little stress often makes succulents look their best. Some species look very different when stressed, others barely different at all. They can also experience varying degrees of stress, with slight stress bringing about a small colour change or “blush,” while fuller stress may bring more drastic colour changes.

Light

All succulents need good light to have their best colour and growth. Without good light, they can never look their best and the colour often fades. In response to strong light, many succulents produce coloured pigments in their cells. These pigments actually serve to protect the plant from damage from the sun; it’s the succulent’s version of getting a “tan.” In general, bright light gives good colour. Some species change back and forth from green to various colours depending on how bright their light source is. Korean hybrids are often very colourful when stressed, but turn green when not. Further, ultraviolet (UV) radiation from the sun can induce a stress response in succulents. This is why sometimes natural sun (UV) and grow lights (bright light but usually no UV) can produce plants that look a bit different. If you purchased a colourful succulent and it faded or turned green, this is usually because the light it’s growing in is not as strong as before and not strong enough to induce the colour pigments. Some need just a little direct sun to become stressed, others need full sun to reach their most colourful state. Excessive hot sun can be too much however, causing damage or a faded look.

*Sedum rubrotinctum* *– full sun stress*

Temperature

In succulents’ native environments, seasonal temperature changes can trigger stress responses and dramatic colours. In general, excessive heat stress can make the plants look faded or “tired,” but cold stress can cause brilliant colours to emerge. For indoor/tender succulents, “cold” means 3-10C. Definitely not Canadian cold! Many of these succulents can tolerate and survive a brief frost but it’s not advisable to expose them to conditions lower than 3C or they may be damaged or killed. I keep many of my tender succulents in a sheltered greenhouse over the winter. Temperatures range from 3-15C, and a heater automatically comes on at 3 degrees and turns off at 5 degrees. Coastal BC is mild so the heater remains off most of the time but becomes crucial during overnight frosts or during arctic outflows. The succulents stop growing and take a rest, requiring very little water from November – February. Some varieties develop their deepest colours in this time. For most people in Canada, keeping tender succulents outdoors in a greenhouse over winter may not be feasible, but if you have your succulents outside in the fall/spring to expose them to cool (but not freezing) temperatures, they may develop cold stress colours. Be sure to keep the soil fairly dry and protected from rain if you do this, as cool temperatures plus moisture can cause rot.

*Variegated echeveria subsessilis – plant on left has cold stress, giving pink hues*

Drought

Drought is the final way to induce stress in succulents. In their native environments, succulents are sometimes forced to endure weeks or even months without water. These periods of drought induce stress colours in some species. Even in strong light, some plants may remain green if watered regularly, but become colourful after drying out. Plants that are larger or well established respond best to drought stress. Very small or not-established plants may simply wither or die if exposed to drought. If the plant starts to look shrivelled, it’s time to water- it’s getting too dehydrated. Sometimes drought stress is not achieved until the roots have filled the pot. In the past I have purchased cuttings from stressed plants, often colourful. Once planted, they often revert to green while rooting but become colourful again later after the roots filled the pot. When roots fill a pot, the soil drys out faster after watering, resulting in more drought and stress response.

*Freshly planted Crosby’s Prolific *aloe* – no stress; green* *foliage*

*After 1 year – roots have completely filled pot; sun & drought stress*

*Echeveria Romeo Rubin – drought & sun stress (L), sun stress (R)*

Final Thoughts

Stressing succulents for deepest colour is a skill and an art that is best achieved after first learning the basics of succulent care (water, light, soil). If you are new to succulents, focus first on learning how to water appropriately and how to give the plant good light. Further, note that it can be difficult to stress plants indoors without grow lights- after all, succulents naturally grow outside, with plenty of sun and seasonal changes of temperature and water. This is why many people move their succulents outside in the summer (just make sure to do so according to the care instructions). Indoors, a sunny windowsill with full exposure can often yield good results in the brighter months of the year. Growing plants with grow lights for approximately 12 hours per day and allowing them to dry out between watering can also give good results. With no UV or cool temperatures, they may not be stressed to their full potential, but still look very attractive/colourful.

Do not expose succulents to stressful conditions suddenly. Sudden exposure to too much light/UV can cause burn. Many times (many, many times 🙂 ) I have made the mistake of placing plants in UV too quickly or too strongly, resulting in burn. Sudden exposure to “cold” is more forgiving, but it’s still best not to go from warm to cold suddenly (moving plants outside with overnight lows of 6-8C should be fine; 1-3C maybe not). Plant stress is best applied gradually and this will typically give the the best results, as these changes in the plants’ native environment occur gradually with the changing seasons.

Succulent stress is best achieved on plants that are established and healthy. If a plant is very small, not fully rooted, or struggling for whatever reason, stressful conditions can be to much to handle and it may be injured or killed. A large, established echeveria may take full sun in stride, while a baby one or an unrooted one may get completely fried in the same conditions.

Remember that there are thousands of succulent varieties, and each is different. Some may look drastically different under stress, others barely different. In general all need strong light to be stressed but different kinds will respond differently to UV, cold, and drought. Good plant care and observation will reveal each plant’s delightful surprises.

Finally, be aware that in the age of social media, plant people often post images of their plants only when they’re at their best. For succulents, this often means fully stressed. In reality the plants are not meant to look this perfect, colourful and photogenic all the time, all year long. Nor do they in their actual habitats. Succulent newbies often purchase chubby, colourful, stressed plants and then think they’re doing something wrong when they don’t look as colourful all year long. We live in Canada, not southern California, and must make some concessions for indoor growing. For some kinds only grow lights can keep them looking their best all year round. Don’t feel bad if your succulent doesn’t look as perfect as others on Instagram- I can 100% guarantee that they don’t look look like that all the time either. Not to mention the excessive use of filters, colour enhancement, etc. As is usual with social media people only want to show their “best.” I am somewhat guilty too 🙂 . Do your best to care well for your plants and learn to accept that they won’t, and shouldn’t, look perfect all the time; but bask in their glory when they do!