Root Rot

Too much of a good thing can be a bad thing. This is especially true when it comes to water in the soil.


Heavy rains (or poorly managed sprinklers) can lead to water stress just as easily as drought. Water stressed plants quickly become susceptible to pests and diseases they would normally be able to handle on their own.


Root rot is a common result of over-watering and poor drainage, especially in houseplants. Once root rot occurs, the plant is doomed. ​

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How does root rot occur?

A healthy plant breathes through its leaves and roots. When flooding or over-watering occur, the macropores and micropores within the soil become saturated with water. These tiny pockets within the soil are normally used to hold and move water and air. If they are filled with water, the air can’t get in and the roots cannot breath.


At the same time, spores of mold and fungal diseases, such as crown rot, thrive in this soggy environment, replicating exponentially and clogging vascular bundles. With the xylem and phloem blocked, the excess moisture can not be eliminated and the food from the leaves cannot reach the roots. Result: death by starvation and asphyxiation.

Photo of root rot from UCIPM

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Symptoms of root rot

One sign of root rot is the presence of fungus gnats. These tiny black flying insects love to eat decomposing organic matter. Wilting is another common symptom of root rot. Leaves may turn red, purple, or yellow. You may also notice darkened areas in the bark at ground level. If you peel the outer bark away, you may see reddish-brown streaks within the inner bark.


Preventing root rot

Since root rot will kill your plants, prevention is paramount. These tips can help:

• Never cover a graft union with mulch or soil
• Never place a tree or shrub deeper than it was before
• Select resistant varieties
• Monitor susceptible plants, such as snapdragon and lavender, closely
• Maintain good soil porosity
• Allow soil to dry out between waterings
• Make sure sprinklers are not set to spray tree trunks

Water is a precious resource and there is no sense in wasting it, especially when it threatens the health of your plants. You may be surprised at how little water plants really need. In light of the current drought, our household has reduced water consumption to only 25% of what it was 3 years ago. I was still able to produce hundreds of pounds of food while maintaining the health of my landscape. 


How do you conserve water in your garden?