Cacti survive the harsh desert climate through their ability to store water in their bodies for use during times of drought. Therefore, they do not need to be watered as often as most other plants. This also means that cacti can easily be overwatered, especially by newbie plant owners, who can be a little too enthusiastic when caring for their first cactus. Just remember that most cacti only need to be watered roughly every 10 days. They have enough water stored, and the soil also needs to dry out between watering.
In this article, we will discuss the causes and signs of an overwatered cactus, and what to do if you have overwatered your cactus.
What happens if you overwater your cactus?
Overwatering your cactus can kill it, so you should always be vigilant regarding your watering techniques.
The cactus loses its color
There are many different kinds of cacti and they come in a wide array of colors and hues. They range from lime green to a deep, dark green color.
When a cactus is overwatered, it will likely become dull and pale. You may not even notice the change in color, since it happens very slowly.
This color change is due to chlorosis, which is a loss of the chlorophyll that gives the plant its color. Chlorosis is caused by nutrient deficiencies and leads to poor flowering and stunted growth. If the roots of a cactus drown in soggy soil they will die, and will no longer effectively absorb nutrients from the soil and into the plant, and the cactus will therefore suffer from nutrient deficiency.
The cactus becomes droopy and soggy
If you overwater your cactus, the excess moisture it takes up will cause it to become soggy and droopy.
The stem of the cactus will feel soft and mushy, and this is a cause for immediate concern. The plant is mushy because its cells have filled with too much water. The water molecules are causing the cells to bulge outwards, increasing the pressure inside the plant tissue. When the pressure reaches a certain point, the cells will rupture, affecting the plant’s internal transport structure so that it can no longer effectively transport nutrients and water.
The longer the overwatering goes unnoticed, the more parts of the cactus will start to droop and fall off. Before you know it, the entire plant will have toppled over.
Root rot
When cactus roots die from a lack of oxygen after drowning in wet soil, they will decompose and become susceptible to opportunistic pathogens. This is called root rot. The rot will first attack the tips of the roots, and then make its way up the plant. It can be tricky to catch root rot in its early stages because the early damage is done underneath the soil. Often the root damage becomes so severe that the cactus can no longer be salvaged. Its growth becomes stunted and portions of the plant may fall off when you touch them. Eventually, the cactus will turn completely brown or black, and die.
What are the signs of an overwatered cactus?
As mentioned above, it can be tricky catching the signs of an overwatered cactus in the early stages. You need to develop an understanding of what a happy cactus looks like, to be able to tell it apart from one that is being overwatered.
What makes this distinction difficult initially are the similarities between a happy and healthy cactus and an overwatered one. The two look very much alike above the soil, while the real damage is being inflicted underground.
Although it is tricky, there are still early signs you can spot that will alert you to possible overwatering.
Leaf drop
In cacti such as the Christmas cactus, the leaves will drop off from overwatering, even if the cactus looks healthy.
Yellowing
If your cactus turns yellow gradually, this is an almost guaranteed sign of overwatering. Salvage your cactus as soon as you see discoloration; do not wait for the entire cactus to turn yellow before taking action.
Soft, mushy stems and spines
As previously mentioned, a cactus will become mushy because of the water molecules filling the plant’s cells and causing the tissue to rupture, thus impairing its ability to distribute water and nutrients throughout its body.
Edema
Edema in cacti presents as brown spots on the surface of the plant. These spots are another result of ruptured tissue due to overfilled cells.
Wilting
If the plant looks sad and droopy, it could point to overwatering.
Brown or black roots
The most telling and obvious sign of overwatering is if you see brown or black roots upon uprooting your cactus to check its roots. If the roots have a putrid smell like rotten vegetation, your cactus has root rot from overwatering.
If you see one or some of these signs, refrain from watering your cactus until you can inspect it and know for sure whether this is due to overwatering.
How do I save my overwatered cactus?
If you have inspected your cactus and are sure that it is overwatered, remove it from the pot and shake or wash off any old soil from the roots.
Check the roots and, using sterile scissors, cut off any brown or black roots. Leave behind all the white roots. Lay the cactus in a tray lined with dry paper towels to allow the roots to dry out. When the roots are dry, replant the cactus in a pot with drainage holes at the bottom, using a well-draining cactus soil mix. Do not water the cactus after replanting it, to give the roots enough time to heal and be able to absorb water effectively.
Make sure you remove any dead leaves and stems from the cactus. If there are stems that are droopy, cut them off. If a stem looks rotted but still has healthy-looking leaves on it, you are better off removing that stem anyway. This will cut off any infection and stop it from spreading any further.
Lastly, the best way to prevent your cactus from being overwatered is to know when and how much to water it. Touch the soil in the pot; if the top two inches of soil are dry, water the cactus. If the top two inches of soil are still damp, wait one or two days and check the soil again before watering.
Conclusion
Overwatering is one of the classic mistakes made by newbie plant owners when trying to grow a cactus. Overwatering a cactus can lead to root rot, where the plant’s roots die due to drowning in soil that is perpetually wet. The dead roots are infected by opportunistic pathogens and the disease travels up the plant and eventually kills it.
Signs of an overwatered cactus include leaf drop, yellowing, mushy stems, edema, wilting and brown or black roots.
Salvage your cactus by removing any dead roots, replanting it in well-draining soil using a pot with drainage holes, and only watering the cactus when the top two inches of soil are dry.
Image: istockphoto.com / Muanpare wanpen