A question that often plagues new cactophiles is that why of all the plants should a cactus get sunburnt ?

It is very natural to think that cacti  occur in the  harshest of all conditions so when exposed to a bit of sun at homes, why do they give up on all of us? Just as kids who are kept indoors, not exposed to harsh realities of life, mollycoddled,  over fed and kept in cool and humid environment and texting being the only physical exercise makes them soft and delicate.  But when suddenly exposed to harsh outside world, without sun blocking creams and goggles – sunstroke , skinburn, headaches are the result  …  you know the story too well !

Soft skin turns brown where plant gets maximum exposure to light and skin dries up crisp.

So what is sunburn ?      Sunburn is damage of cactus or plant tissue due to over exposure to Sunlight of an intensity or duration the plant is not used to or hardened for.

Skin becomes light and pale in color and later turns to a brown scar which may be permanent till the time new growth forces it down towards roots.
Dried up portion after the skin turned pale and yellow

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Before we get to how to prevent this let us go over a few basics:-

“The Survival of all living things on Planet Earth is based upon  Adaptation and Interdependence. Each organism adapts to change in situations. If it doesn’t- it dies ! (In that case too someone or something benefits! Such are the ways of the world)”

  •  A plant is born well adapted to grow in certain light conditions.
  • A plant adapts to a change when grown in other light conditions than what it was suited for.
  • A plant continuously tries to be in synch with the change of environment ( light)  due to  man made changes or  seasonal which are – duration and intensity of light.
  • If we take example of North India – ( Delhi  perched at a Latitude of 28 Deg 40 mins) the Day length from peak winters varies from 10h 20 mins to 14 h in summers .  This 30 percent difference in duration of light is further aggravated by change in intensity of light from winters to summers).
  • A plant continuously adapts to this change through out the year and does not get burnt during change of seasons because Mama Nature gives it the time to do so.

Adaptations are :-

Plants in full sun are of lighter color. Concentration of chlorophyll is less. Shade grown plants are darker and have more chlorophyll to make up for loss of light. (Types of chlorophyll also vary color but that is not pertinent here)

Full Sun grown plants have leaves pointing upwards . This is to decrease exposure of sunlight to leaves.

Plants grown in less sun have leaves fully exposed, flat or horizontal leaves as if wanting to collect more sunshine on the leaves.

 

Plant grown in Full Sun. Leaves point upwards as if with folded hands telling sun enough of light please !  and are light in color.
Plant grown in shade. Leaves are horizontal as if begging for energy from life giving Sun and are darker in color.

 

 

 

 

 

 

 

 

Plants growing in least light become elongated  as if trying to reach for sun. In this  condition a plant is called an  ‘Etiolated Plant’ . These plants are spindly and tall with large inter nodal length. Such plants are trying to reach above the overgrowth around them . Like trying to stick their heads out.

Succulent lovers are very familiar with this problem especially when growing plants in Hot Plains of India.  Light and Heat never balances . Give them more light, the temperature rises and they die either of root rot or burns. And if you grow them in shade your expensive Echeverias turn to spindly and unrecognizable objects of  (un)dezire.

Signs of Etiolation. You can see the stem between the leaves.
Very compact plant with no stem visible.

 

 

 

 

 

 

 

 

How to prevent Sunburn?

  1. Give them time to adapt.  

Lets see how a plant kept in a balcony feels on a typical midsummer day :-

 

Early hours of day plant does not get direct light
Strong noon time direct sunlight for very few hours
Plant gets touch of direct sunlight only after 20 hours or so .

During major portion of the 24 hour hour cycle, the plant is trying to adapt itself to low light conditions but once during the day it is subjected to harsh bright sunlight on its soft skin and thus scorching is  bound to happen.

Also remember that as the season moves into midsummer the sun will creep deeper into your balcony and will assault the little guy who was sitting in the corner. So keep a track of how deep the sunlight penetrates into the balcony with changing arc of sun towards or away from the North Pole.

You have to move your pots to areas where you get light of setting or rising sun which is not so strong in intensity. If you cannot make better arrangements then move them deeper into shade to avoid sunburn.

If you are shifting plants from inside to outside  and want to make your cacti like tough field grown plants which are grown in full sun then I suggest give them time and slowly expose them to stronger light over a period of few days.

Be Sure to rotate the plants towards sun gradually. About 30 degrees at one time and not 180 degrees.

2. Oops! I washed my balcony and my plants got suddenly got sun burnt even though I did not relocate them at all!!!!    Well in all probability what happened was though the plants were kept in the same location, the pots got rotated. That is, the sunny side is now facing shadow side, which is not a problem but the side that was facing the shadow side is now facing sunny side. Now that is a problem. Prolonged exposure to less light on one side of the plant had  made physiological changes on that side to compensate for less light . Portion in shady circumstances – suddenly exposed! Devastating!

Heat from floor damages plants in pots on the floor. Raise pots by benching.

3. Protection from radiated heat from concrete.   Plants on open terraces or sunny balconies which have smooth tiles or just brick and mortar construction have plants showing summer stress. They stop growing and become dehydrated and suddenly will show signs of root rot. Either root rot will infect the core of the plant or it will get arrested at the junction of the root and body and plant will keep on shrinking.

This happens because the plant gets extra light reflected from the surroundings and heat which is absorbed and re-radiated by concrete floor. Pots kept on floor are greatly affected and may wilt. To avoid this use any kind of benching to raise the pots off the floor.

4. Overheating of Pots.   Pots by nature are heat traps. They have high volume compared to the top surface area. The sides of the pot which are incident to the rays of the sun trap heat and the surface of the pot releases this heat slowly.

Porous grains with adequate space between grains helps in evaporative cooling, Respiration of Roots and insulation.

Lot actually depends upon the nature of media used and the type of pot used. If media is dense and clayey -siliceous- micaceous mix , it will trap more heat due to its specific heat capacity while the porous media with both inter and intra-granular porosity will trap less heat.

Everyone likes to display their Cactus babies in best possible attire (God knows why they need more names when they have such cute Latin names!)  So a choice of pot helps to kill the plant.  Ceramic pots are best suited to kill plants because of their thick non porous walls. They retain heat for a long time to roast the roots. Remember we are talking about an Indian Summer in North India.  Next best are plastic pots to kill a plant.

Terracotta Pots Ideal for plants grown in warm areas

 

 

Basic Earthy Terracotta pots are most suited to keep the plants alive. Their thick porous walls do not trap heat . Air cavities act as insulators and the pores permit evaporative cooling.

And another thing is that if you water your cactus and succulents to keep them cool during the hottest part of the day – the nursery men will surely benefit. Never water a cactus pot to cool down the pot. The roots will turn into mush and cactus or succulent will rot and die.

A very rare and delicate crest nestled in pot in pot concept.

In case, you do not want to change a plant from ceramic to terracotta because they take a long time to establish. In that case you can insulate the small pot by inserting the pot into another bigger pot having porous media. The outer pot keeps the inner pot cool without having to be over-watered.

 

 

5. What about the Sun itself?  Well how to tackle Ra, the Sun God. The best way to tackle sun is by using shade nets. The advantage of a shade net is while the sun does not burn the plant down it permits an all around growth. No etiolation or leaning,  also a cactus or succulent is more compact and beautiful under a shade net. If configured appropriately they can also prevent damage from hail, squirrels, monkeys and prying eyes.

View through a 25% shade net
Color of shade net is not important but the amount of sunlight it blocks.

Shade nets work in two ways :-

a.        They block a portion of sunlight . They usually come in the following              percentages – 25%, 35%, 50% and 90%.  The best suited for cacti are obviously 25 % . A 25% net implies that 25% of light is blocked.

b.         The net because of its loose fabric moves with wind and  prevents concentration of light on one portion of the plant. Coupled with this, the close weave of net fabric keeps the shade portion moving over the plant due to the movement of the sun across the sky.

In case you have to move a plant from inside to outside and place under a 25 percent net permanently, the best way would be to move it under 2 layers of 25 % net or a 50% net for some time as an acclimatization measure.Extra netting can be removed after a week or so.  ( Though remember that  2 drapes of 25 % is not equal to 50 percent but is is 43% only)

And Last but not the least –

What to do when a plant is sunburnt beyond its aesthetic value?  Nature has programmed all of us, ie all the living things with certain amount of recuperability . If there is living tissue left ( green ) the plant will have new growth in months or years . Just keep it in some corner of your growing place. Don’t disturb it much . Send it good vibes and soon it will forgive your mistakes.

If it doesn’t recover you must throw it away in some flower bed or foliage pot.  The bacteria and fungi will break it down and recycle the nutrients to mother earth. In any case do not dump a dead cactus in another cactus or succulent pot. Same saprophytes may work on the living plant.

And if you do get melancholic about  the loss of a beloved plant . Click on store  here and shop to your hearts content and get rid of your depression.

 

 

 

 

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