Orchid Root Rot

Orchid Root Rot

Orchid plants, with the scientific name Orchidaceae, are flowering plants with over 25,000 species distributed around the world. These perennials are popular indoor plants with flowers that come in a variety of colors, including white, purple, yellow, pink and green. They are terrestrial or epiphytic, depending on the species, and like most plants, may be prone to root rot if their growing conditions are not ideal. 

What are the signs of root rot in orchids?

Your orchid plants are probably developing root rot if the flower buds are dropping from the spike for no apparent reason. The plants may not be producing new blooms, and the leaves may be soft, limp and floppy, instead of tough and firm. The exposed roots will look withered and dark brown or black, rather than firm and green or white in color. They may be soft to the touch and feel mushy if you squeeze them between your fingers. The first visible signs of root rot will be those in the roots.

What are the causes of orchid root rot?

Orchid root rot usually develops if water remains stagnant in the potting medium for a long period. This happens if you use pots with no proper drainage holes, or if you overwater your plants. The roots will likely start to rot if the potting medium does not dry out between waterings or if it is packed too tightly around the roots. Air circulation and oxygen supply become restricted if there are no air spaces in the potting medium, and the root system suffocates. 

Potting medium that is packed tightly in the pot could also lead to a decreased ability to drain water. The resultant exposure of the roots to moisture for extended periods could destroy their delicate velamen covering. The roots will then be unable to absorb nutrients and water, and may eventually die. 

Root rot can also be caused by pathogens, including bacteria, mold and fungi. These pathogens need a moist environment to thrive and multiply, and once they do, they can infect roots that have already been weakened by waterlogging. Once inside the roots, they will either promote root rot or exacerbate an existing infection. These pathogens may also attack the plant through damaged stems, which is known as crown rot. 

How to treat orchid root rot

You can treat orchid root rot by removing the plant from its pot and inspecting the roots. Gently pull the plant out of the pot and brush off any growing medium stuck between the roots. Rinse and clean the roots gently in lukewarm water.  

Look for any dark brown or black roots and check for mushy tissue. Cut off the dead roots one at a time with a pair of sterilized gardening scissors or shears. For extra safety, sterilize the scissors after each cut to prevent the spread of pathogens. 

To make a sterilizing solution, mix one part bleach with nine parts water to make a 10% bleach solution. Spray the cutting tools after each cut and allow the tools to dry so the solution does not get onto your plants. After the infected roots have been removed, repot the orchid in a new pot with fresh potting medium. If you prefer to reuse the old pot, soak it first in sterilizing solution for an hour and allow it to dry before planting the orchid. 

How to prevent orchid root rot

To prevent root rot in orchids, use well-draining pots for your plants. These pots should have holes or slits cut in the sides. The holes allow good airflow and circulation as well as proper drainage. Water the plants only when the potting medium is dry and see to it that the pots never sit in water for long periods. 

Keep your orchids in a well ventilated environment, since air movement is essential for these plants. Open the windows or turn on the fan to promote good air circulation. You could also take the plants outside during warm weather, but make sure that you place them in a protected spot with no direct sunlight. 

Do not mix different-sized potting medium components. Smaller components will fill the gaps between the bigger materials, and this will reduce the number and size of air spaces inside the pots and between the roots. Loosely place the potting medium in the pots and around the roots when repotting the plants, to provide ample space for drainage and circulation. 

Repot the orchids at least every one to two years. Terrestrial orchids should be repotted at least every three years. While doing this, you can inspect the roots that you would not otherwise see. 

Repotting also allows you to refresh the potting medium. Organic potting media eventually mature and decompose over time, and this creates a dense environment more akin to potting soil.  

Conclusion 

Orchids are popular flowering plants that are widely propagated around the world. These perennial epiphytic herbs can be susceptible to root rot because of overwatering, poor drainage, and pathogens like bacteria, mold and fungi. You can save your affected plant by removing it from the pot, cutting off the infected roots, and repotting the plants in new pots with fresh potting medium.

Image: istockphoto.com / alexytrener