Stressing succulents for vibrant, summer colour can occur as a happy accident. With the current warm weather in Melbourne, you may have noticed this occurring in your garden, where you’ve left succulents in sun filled positions throughout summer. The colours should be rich and vibrant, not dull and washed out in appearance.
Common succulents that change colour when stressed in summer …
Succulents known to change colour in summer due to stress are common aloes and crassulas, some kalanchoes, sedums, echeverias, aeoniums, euphorbias and sempervivums. Aeoniums shown below are winter growers. They close up and shut down in summer, but their colours can be amazing, particularly, the reds and purples like those shown below. Images taken while walking around the wonderful gardens at Roraima Nursery in Lara.
Often the common name is a bit of a give away too, for example Crassula capitella ‘Campfire’ , Crassula ovata ‘Hummel’s Sunset‘, Euphorbia tirucalli ‘Firesticks’. Other common succulents that change colour are as follows:
Sedum rubrotinctum (Jelly Bean Plant)
Kalanchoe luciae (Paddle Plant)
Crassula ovata ‘Hummel’s Sunset‘
Crassula ovata ‘Gollum’
Euphorbia tirucalli ‘Firesticks’
How to stress a succulent in summer to produce vibrant colour?
- To stress your succulent you first have to determine if it is a succulent that changes colour when stressed. Some succulents won’t change colour at all. As a rule, succulents which are silver in colour or entirely green will not change colour at all.
- Observe the plant. If your succulent leaves have red margins or show a blush of a different colour in their leaves, there’s a good chance that this variation in colour will be enhanced with strong sunlight over summer. Take the common jade plant, Crassula ovata. This plant colours beautifully with stress, particularly, Crassula ovata ‘Hummel’s Sunset‘ also known as the Golden Jade tree. It has an obvious red margin that can turn a lipstick pink with sunlight while the rest of the chubby leaf changes from green to varying shades of yellow and gold. The combination of all three colours (red/pink, yellow and green) throws up a variation that is quite striking under stress and is considered rather ornamental. Other examples are Sedum rubrotinctum (Jelly Bean Plant) with green succulent leaves like jelly beans in winter that turn shades of green, red and orange in summer. Aloes in shade will stay a deep green colour but will turn pale pink in varying degrees of sunlight.
- Experiment with placement. Try placing a common plant like the Crassula ovata ‘Hummel’s Sunset’ in different positions. Place one in shade, and others in filtered light, morning light and an all day sun position, If the full sun position starts to burn leaves then move it to a location that is less extreme, ie: sunlight up until early afternoon for instance.
- Slowly introduce your plant to sun. Let them acclimatise. The seasons generally do this for us but it would not be wise to move a plant in shade to a full sun position on the first hot days in summer. Like us their virgin leaves (skin) will burn with a rash introduction to intense heat.
- Preparation. It is best to start moving plants once winter frosts are well and truly over and spring has sprung. Then let them slowly acclimatise to their new positions in early spring stretching the hours in the sun as summer approaches. Most succulent do not like bearing the full brunt of late afternoon sun in summer so keep this in mind too. Offering protection after 2pm is wise once in the full throes of summer.
- Direct sunlight. You will need to place your succulent in a position that gets direct sunlight for several hours a day, morning to early afternoon sun is best. Further stress can be applied by restricting water and potting the plant into rich soil which they are unaccustomed to. The vibrant colour change is most evident as heat and sunlight intensify during summer. Your plant will change from green to shades of yellow, pink, orange, red and deep purple depending on the succulent. As long as the colours are rich and vibrant, not washed out and dull and the leaves are healthy looking, not burnt and shrivelling, then they are fine to dance in the sunlight. If they are suffering, it is wise to return to a more shaded position to rest and rejuvenate.
Why do succulents change colour with stress?
In very basic terms, certain succulents turn vibrant in colour when exposed to sun. What happens is not dissimilar to the way our skin reacts when exposed to sun. We produce more melanin when exposed to the sun which colours our skin (tan) and prevents us from burning. Plants have pigments which work in much the same way. Pigments in plants know as chlorophyll (green colour in plants), cartenoids (produce colours ranging from yellow to orange) and anthocyanins (reds to purples). In shade most succulents turn green as chlorophyll is responsible for capturing sunlight for photosynthesis. When a plant is exposed to extreme sunlight and heat without water, plants produce the pigments, anthocyanins and carotenoid to protect themselves.
We will return to this topic in spring to prepare our plants for next summer. Over coming weeks we will focus our attention on Autumn: propagation, tips and advice and jobs to do in our succulent gardens to prepare us for the cold, wet, frosty and wild weather of Winter.