Cacti are some of the hardiest, most resilient plants on earth, designed to survive some of the planet’s harshest environments.
While they do not typically encounter many problems and have very basic growth requirements, one of the common problems encountered by caucus owners is the plant growing longer and thinner than it should. This is known as etiolation.
The most common reasons for etiolation are that the cactus is not getting enough light, it was not moved to a sunnier spot as soon as spring started, or it was unable to go dormant over winter.
In this article, we will discuss more about how these factors cause etiolation, what you can do to fix the problem, and how to avoid it from occurring in the first place.
Why is my cactus growing tall and thin?
It is possible for cacti to become etiolated – or tall and thin – for a number of reasons. These include not receiving enough sunlight, an unnatural difference between the light levels and the temperature they are receiving, and not being allowed to go dormant during the winter months.
Cacti, especially desert species, require a lot of sunlight to survive and to thrive. Although they can be grown indoors, they still require direct light to grow optimally.
In the absence of sufficient light, the cactus will suffer a gradual loss of body mass, and will become etiolated, whereby its stem begins to grow at a faster rate in search of light. This growth may be misinterpreted as a positive sign, but it is not. Despite the faster rate of growth, the stem will become longer and thinner than it should naturally be. Some cacti even become paler and more pointy as a result of this process.
Often, this problem starts when you move your cactus from the outdoors to an indoor spot. However, it can also happen if the plant is kept outdoors in a shady area, or if all sides of the plant do not get equal exposure to sunlight. In the latter case, the cactus will grow unevenly, with one side stretching out more than the other.
The outdoor temperature is high but the plant still does not get the light it needs
It is imperative that the plant is exposed to sunlight as soon as the temperature begins to rise in the spring. This is because the raised temperature is a signal to the cactus that the growing season has arrived, and this should be accompanied by higher levels of sunlight. If it experiences a temperature increase with no concurrent increase in light, it will begin to grow long and thin in order to reach more light.
This can happen if you have kept the plant indoors over the winter and do not take it outdoors soon enough when the temperatures rise in spring. It will awaken from its dormant state as a result of the increased temperature, but there will be no light to greet it.
The cactus is unable to go dormant
Your cactus requires different care depending on the time of year. You must ensure that it receives this seasonal care by allowing it to grow to its maximum potential during the warmer seasons and remain dormant during the winter months.
When winter arrives, the correct course of action is to bring your cactus indoors, but you must also significantly reduce your frequency of watering during this period. If cacti continue to receive water but no light, they will be unable to go dormant and will continue to grow instead. And, considering the lack of light, their growth at this time will be unhealthy and etiolated.
How can I fix a cactus that has grown tall and thin?
Once your cactus has become etiolated, the skinny parts of the plant cannot be returned to their normal size and thickness. The best you can do is cut off the skinny parts to preserve the plant’s aesthetic.
Use the etiolated limb to propagate the cactus
Removing the thin parts not only preserves the plant’s aesthetic; it may also keep the cactus from falling over or breaking due to the weakness of the etiolated limb.
This usually happens when the plant is moved to a sunnier spot without removing the skinny part of the limb. The new growth on top of the etiolated section will be normal; this can cause the limb to become top-heavy and the skinny section will snap from the weight.
To prevent this, cut off the skinny section using a sterile knife, and if you do not want to waste it, you can use it to propagate the cactus.
It is best to wait until the warmer months before pruning and propagating the plant because this is when it is actively growing so it will recover faster from the process.
To propagate the cactus, place the pruned section on a dry surface for a few days to allow it to callus over. One week in a shaded room at room temperature should do it. Once the cut end has hardened, the callus has formed and you can now plant it.
Select a new pot and check that it has drainage holes at the bottom. Drainage holes are important because they allow excess water to escape from the soil, thus reducing the chances of overwatering and root rot.
Place a layer of pebbles at the very bottom of the pot, followed by half an inch of charcoal on top of the pebbles.
Fill the rest of the pot with a well-draining potting mix made for cacti or succulents. Plant the callused end of the cactus section in the soil, about an inch or two deep. Pat down the soil around the stem to keep it stable and upright.
Wait a week before watering the soil, and thereafter only water it when the top two inches of soil are dry. Remember that overwatering can lead to rot which can kill the plant.
Do not mist your cactus; if the water on the foliage does not dry off fast enough, this can encourage fungal growth that can harm the plant.
Place the pot in a spot that gets plenty of light. After three to four weeks, you can check on the root development by gently pulling on the plant. If you feel resistance, that means the roots have anchored well and you can now care for the plant as you would a normal cactus.
Give the cactus more light
The most important thing to do if your cactus has grown tall and thin is to rectify its lighting situation and make sure it gets all the light it needs going forward.
If you were keeping it in a shady or semi-shaded area outdoors, try placing it in an open space, in full sunlight, and see how it fairs.
If you keep the plant indoors, place it near a window that lets in sufficiently bright light.
Also, remember to rotate the pot every couple of days to give all sides of the plant some time in the light. This will prevent the plant from growing faster on one side than the other, and it will grow straighter and more evenly.
Use a grow light
If you happen to live in a place where natural sunlight is scarce for certain months of the year, you may need to use the help of a grow light for your cactus.
Of course, natural sunlight is still the best option, but artificial light will be a sufficient alternative.
A cactus will grow tall and thin if it does not get as much light as it needs on a daily basis. This is called etiolation, and it is the plant’s way of adapting to a lack of light. It essentially concentrates all of its energy and resources into growing a long, thin limb to reach the nearest source of light. This is an indication that the plant is desperate and struggling to survive.
If your cactus has become etiolated, transfer it to a sunnier spot immediately. The thin limb will not harm the plant, but if a normal limb grows on top of it, the thin part might break and damage the plant. You can prevent this by removing the thin limb, and you can use the cut piece to propagate the plant, should you wish.
Image: istockphoto.com / Thaisign