The subject of how much sun succulents need is always a hot topic among succulent lovers, newbies and experts alike.  How much is too much?  Is morning sun ok but afternoon is a no no?   Will my succulent die if it gets too much sun? What is the definition of full sun, partial sun, dappled sun, partial shade and full shade?

Photosynthesis is a process used by plants to convert ‘light energy’ (the sun) into chemical energy that can be released to fuel the plants’ growth. In low light, plants need to absorb maximum light for photosynthesis if they are to survive. In high light the plant needs to reflect some light for photosynthesis if they are to survive.

What is the definition of Full Sun/Partial Sun/Partial Shade/Dappled Sun & Full Shade?
Some succulents prefer full sun and some prefer partial shade, partial sun and a few prefer full shade, but what does this mean. I found the definition below on a gardening website which clarifies the meaning of these requirements.

  • Full Sun means 6 full hours of direct sunlight. The six hours could be from 8 – 3 or 12 – 6; anytime during the day. The hours can also be three morning hours, plus three afternoon hours.
  • Partial Sun / Partial Shade: These two are interchangeable to mean 3-6 hours of sunlight each day. While the terms are interchangeable, there is a default understanding.  Partial shade refers to morning and early afternoon sun, while a plant listed as partial sun means relief from the intense late afternoon sun  ie requires shade from a structure or a tree.
  • Dappled Sun is similar to partial shade. The plants are getting partial sun as it makes it’s way through the branches of a tree.
  • Full Shade means less than 3 hours of direct sun each day, best if it’s morning sun. But even in the absence of  direct sunlight, full shade can be bright light. Plus, full shade likes a filtered  sunlight the remainder of the day. Every plant needs some sun; even those that thrive in full shade.

The above would only be a guideline.  This does not mean that if your succulent has more than 6 hours of sun you need to move it to shade or it will die. Some areas of my garden receive sun from early morning to late afternoon which is more than 6 hours. These have succulents growing and coping well with the large amount of sun they are receiving.

What is the different between morning and afternoon sun?
Many succulent enthusiasts advise that succulents prefer morning sun for optimum growth.  I am unsure why exactly. From a Iayman’s point of view I would say that morning sun is less strong/vibrant than afternoon sun.  Morning sun is less intense and less heat is generated from the sun in early morning. However, I have searched the internet and I am unable to find any science to explain the real difference between morning and afternoon sun.  As per the previous paragraph ‘full sun’ can be 6 hours of sun whether it be in the morning or the afternoon.

Aeonium Pinwheel

Aeonium Pinwheel

Echeveria Elegans

Echeveria Elegans

Echeveria in full sun

E. Strawberry Heart

The succulents above have survived and thrived 6 hours of afternoon sun!

Can you tell by looking at the succulent if it will cope in full sun?
There are some succulents which have characteristics that give us a clue as to whether the plant will grow and cope with full sun. Succulents such as the Cotyledon Orbiculata, some Echeveria and some Kalanchoe have a waxy coating on their leaves.  These succulents grown in full sun will produce copious quantities of the white waxy coating.The coating reflects a high percentage of the sun’s light.  The coating is thicker in full sun and less so when not required. Similarly a coat of hairs on Sempervivum leaves protect the plant from a high percentage of the sun’s light.  In general, plants that cope in full sun have small thick leaves as opposed to shade plants have large thin leaves.   

Kalanchoe

Echeveria with white powder protectant

Echeveria

cotlydon

Cotlydon

Examples of succulents with waxy coating protectant 

Can succulents get sunburn?
Yes succulents ‘can’ get sunburn!  It looks exactly what you think it would look like – brown or black markings along the leaves that are facing the sun.  The good news is that it will not ‘usually’ kill the plant, the succulent will recover.  It happens when a succulent has been grown in the shade or partial shade and then moved to sun/full sun.  The new leaves that are produced while in the sun position will cope with the sun and not get sunburn. When the leaves that have been burnt get older they will shrivel and die just like any other non sunburnt leaves on the plant.

Sedum succulent with sunburn

This Sedum was sunburnt when i moved it to full sun. As you can see the leaves on the top are strong and healthy.

Some points to remember.
– Even though a succulent may be able to survive full sun be aware that air flow is very important.
– Succulents will adapt and evolve (acclimatise) according to the amount of sun/shade they receive.
– Plants can change their leaf angles and orientation in response to a change in sun conditions.

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