How Much Sun Do Cactus Need?

Cactus plants have a voracious appetite for sunlight and may need at least 8 hours of indirect exposure to the sun per day. This is why indoor cacti should be kept in a south-facing window to help them receive as much sunlight as possible.

Moreover, there is a large variability in the sunlight requirements for different cacti species. This means you should know as much about your cactus plant as possible, including where it’s from and the species.

Number of Hours of Sunlight that Cacti Need

Most cactus species need a minimum of 4 to 6 hours of sunlight to survive. But you should dial up this number to 10 hours if you want your plant to really thrive. Cactus plants prefer bright and sunny areas.

Cacti plants that don’t receive enough sunlight will show you a number of disturbing symptoms. You may not notice them stretch and become leggy.

Cactus plants that are not receiving enough sunlight will develop a pale color or revert to a bright green color. On the other hand, cacti plants that receive enough sunlight will exhibit a wide range of beautiful colors.

Does a Cactus Plant Need Direct Sunlight

Although some cactus plants do well under direct sunlight, others may get discolored or even die from being exposed to too much sunlight. It would help if you did all you can to protect your cactus plants from intense heat and direct sunlight.

Many gardeners assume that cacti need direct sunlight, but this is little more than a myth. Cacti can survive direct sunlight, but the word thriving is an altogether different meaning.

Cactus plants grow well when they receive several hours of indirect sunlight. You may use LEDs for additional lighting if sunlight isn’t possible.

It’s important to think of their sunlight needs on a spectrum. Too much and your cactus may develop brown spots with deep scars and die from sun damage. Too little, and your cactus will develop leggy foliage (in a bid to seek sunlight) that doesn’t look very pleasing.

It should be noted that shade-loving cactus species, such as Easter Cactus and Mistletoe Cactus, are more susceptible to sunburn. This is also true for newly propagated cactus plants. That said, cactus plants with lots of spines tend to do well under direct sunlight.

Not all cactus species are sun hardy, but you may be able to train your cactus to survive direct exposure. This is done by slowly acclimating the plant to the intense heat by gradually introducing them to direct sunlight.

Start by positioning the cacti under partial shade and slowly expose them to more sunlight until they become well-adjusted to the sun’s heat. This can be done by exposing them to the morning sun, usually less intense, and then slowly working your way up to the intense sunlight in the afternoon hours.

Another alternative is to position the cacti under the shade of taller plants before moving them to direct sunlight.

This strategy allows you to ‘train’ the plant and minimizes the stress caused to it. If done right, you can prevent sunburning and permanent scarring often caused by direct sunlight.

This strategy will not work well with newly propagated cacti plants because they don’t do well under direct sunlight. Allow them to mature before introducing them to direct sunlight. Different areas of your home will receive varying amounts of sunlight; it will take trial and error to determine a location that suits your cacti best.

As a rule, most people find good results by placing their cacti plants in a south-facing window. In any case, monitor the plant under different sunlight conditions to see how they respond. If you see the formation of unusual brown spots and scarring, it probably means that the plant isn’t doing too well and needs to be relocated to a spot that receives less sunlight.

Can a Cactus Houseplant Survive Without Sunlight?

Cacti use CAM photosynthesis, short for Crassulacean Acid Metabolism, to help them cope with limited water and sunlight. Thanks to CAM photosynthesis, cacti can conserve energy during periods of extreme drought and restricted sunlight by storing carbon dioxide in their systems.

Note that CAM photosynthesis buys cacti more time until they receive more sunlight. Going without sunlight for too long will eventually result in the plant’s death.

What Happens if Cacti Species Receive Too Much Sunlight?

As mentioned earlier, too much sunlight can lead to sunburn and severely damage your cacti plants. What’s even scarier is that the symptoms of excessive sunlight will manifest very quickly, especially during a heatwave or when the temperature gets too high. Sometimes, heat damage may occur gradually.

The most common sign of a sunburned cactus is the formation of brown marks, yellowing of the leaves, and various other types of scarring. If your cactus plant shows these symptoms, it may be time to move it into less intense light conditions over a few days.

This will allow the cactus in California to make a full recovery. You can relocate the plant to its original location once you have verified that the leaves have fully healed. As long as you intervene on time, you should be able to revive the cactus plant.

When reintroducing the plant to sunlight, ensure it is partially faded from the sun.

What Happens if My Cactus Doesn’t Receive Enough Sunlight?

Cactus plants that do not receive enough sunlight will eventually become weak and unhealthy. The most common signs of a lack of sunlight include:  

  • Brown or black spots on certain areas of the cactus
  • Discoloration of the spines (this is usually because the spines never change their color when they are healthy)
  • Not growing

If your cactus plant shows these symptoms, you should introduce it to more sunlight for at least four hours per day. The good news is that reviving your sun-deprived cactus is easy with enough care and attention.

The plant may take a few weeks to recover fully, but you should keep at it!

Protecting Cactus From Extreme Heatwaves

The harsh summer months can be extremely difficult to deal with, especially if they last for several weeks. You could lose your cactus plants if you leave them unprotected. You can do a few things to protect your plants until the climate returns to normal.

Provide Shade   

The best thing you can do in the case of a heatwave is to find shelter for your cactus plants, especially the smaller and fragile ones. Move them to a shadier area of your garden, and if possible, take them indoors. The more mature and healthy plants may be able to survive the harsh conditions, but you should still observe their reaction to the heatwave.

Don’t Repot the Plant

Repotting can be very stressful for your cacti plant because they have to acclimate to a new environment. Doing this at a time when the temperature is excessive can make things worse. It would help if you waited until the temperature returns to normal before you repot the cactus in California.

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Don’t Fertilize During a Heatwave

Ferritization is a great way of helping cactus plants grow steadily. But you should know when it’s time to fertilize them.

As a rule, you should only fertilize the plants during the spring months when they are growing. Introducing fertilizer during a heat wave could be detrimental to your plant. All those extra nutrients may only lead to more damage than good.

Things to do in a HeatwaveThings to do During a Cold Spell
Relocate the cactus indoorsRelocate the cactus indoors
Don’t fertilizeDon’t fertilize
Don’t repotDon’t repot
Provide shadeCover the plants with a cotton sheet

Wrapping Up

So there you have it, an in-depth look at how much sun cactus plants need. To recap, you should provide at least 4 to 6 hours of indirect, bright sunlight. If possible, you should aim for at least 12 hours of indirect sunlight for the best results. And if you live in a spot that does not receive adequate sunlight, consider buying artificial lights that mimic sunlight to help your cacti plants grow.

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