Root rot in house plants

What is root rot?

Root rot is a common problem that affects many house plants and is caused by a fungal infection that affects the plant's roots. It’s not a disease but rather a disorder that occurs when the roots of a plant become waterlogged and can no longer take in air, leading to the decay and death of the root tissues. Root rot is usually caused by overwatering. It inhibits the plant's ability to take up nutrients and water, leading to poor growth. If left untreated, it can ultimately result in the death of the plant.

Root rot treatment

In this video guide, house plant rescuer Sarah Gerrard-Jones suggests how to spot root rot symptoms and how to fix root rot.

What does root rot look like?

Identifying root rot in house plants is crucial for timely intervention to prevent further damage. Some common signs of root rot include:

• Yellowing or wilting leaves: when the roots are affected by rot, they cannot absorb water and nutrients effectively, leading to the plant showing signs of stress, such as yellowing or wilting leaves
• Brown or black roots: healthy roots should be white or light tan in colour. If you notice that the roots of your house plant have turned brown or black, it could be an indication of root rot
• Foul smell: rotting roots emit a foul smell due to the decay of the root tissues. If you notice an unpleasant odour coming from the compost or the plant's roots, it may be a sign of root rot
• Mushy or slimy roots: healthy roots should be firm and have a fibrous texture. If the roots of your plant feel mushy or slimy to the touch, it may be an indication of root rot
• Stunted growth: root rot can lead to stunted growth. If you notice that your plant is not growing as vigorously as it should, despite providing adequate care, it may be due to root rot

House plants affected by root rot

Some house plants are more susceptible to root rot than others due to their specific care requirements and environmental conditions. Plants that need moist or humid environments, such as ferns, peace lilies, and pothos, are less prone to root rot if overwatered or if the compost does not drain properly, while cacti and succulents, which need a free-draining compost, can get root rot more easily. Additionally, plants that are kept in pots without drainage holes or are planted in poorly draining compost can also be at risk of developing root rot.

How to get rid of root rot

Once established, root rot is difficult to treat. The best you can do is to take the plant out of its pot, remove the parts of the plant that are affected (including the roots) and repot into fresh compost. If the rot is visible on most of the plant's roots and foliage, it's unlikely that you will be able to save the plant. However, if there are some healthy roots left, you may be able to bring it back to health using the following steps:

• Remove the plant from the pot and gently shake off excess compost from the roots
• Trim away the affected roots using clean and sterilised pruning shears. Cut the roots above the damaged area and discard the dead roots
• Allow the plant to dry out for a few hours or overnight to allow the roots to recover and to prevent further decay
• Repot the plant in fresh, free-draining compost, and make sure the pot has drainage holes to prevent water from sitting in the bottom
• When repotting, avoid compacting the compost for stability, as this can push oxygen towards the surface when watered, creating favourable conditions for rot to develop. If the plant needs support, use a cane instead

How to prevent root rot

The easiest way to prevent root rot is to avoid overwatering. Water the plant only when the top 3cm of compost feels dry, and allow the water to drain from the pot before returning it to its saucer, so it doesn't have to sit with wet roots for long.

Other way to prevent root rot include:

• Avoiding using heavy, moisture-retaining composts, especially with plants such as cacti and succulents
• Ensuring proper drainage by using pots with drainage holes and using free-draining compost mixtures that allow excess water to flow freely. Adding perlite and horticultural grit can also aid drainage
• Using terracotta pots, which are porus and dry the compost out more quickly
• Promoting good airflow: adequate airflow around plants that like particularly arid conditions such as cacti helps them to draw up and use water properly. Avoid overcrowding these kinds of plants and ensure that they have enough space to breathe