We often talk about root rots as if it is just the result of too much water around the roots of plants. However, if is of course, the result of a disease which is usually a fungus and which is encouraged by high levels of moisture in the root zone.

There are several microscopic organisms that cause root rot. Almost without exception, they require constant moisture to thrive and sustain themselves. Some plants are adapted to living in wet soils and are usually resistant to these diseases. They have developed mechanisms to resist the invasion of the fungus. Many other plants that need a well drained soil may be highly susceptible to root rot diseases.

A few of the more common types of root rot that may be encountered in the home landscape would include:

Root rots are generally promoted by high soil moisture content and warm soils so the real problem is often poor drainage. Root rot is very unusual in well-drained soils such as sand and is very common in those high in clay content. Over-watering, unusually heavy rain seasons and hard pan soils may all contribute to the development of root rot.

When the roots rot away, it inhibits the plant's ability to take in water so, the key symptom is wilting of the leaves and twigs above ground. Infected roots turn reddish-brown or black, become brittle and die.

  1. Proper Drainage - Plants that are especially susceptible to this root rot must be planted in sites that have good drainage. Sometimes amending the soil with porous material or planting in raised beds may avoid the problem.

  2. Planting Depth - Be sure to set plants in the soil at the same depth at which they were growing in the container or at their previous site. Planting too deep and burying the base of stem may stress plants and encourage the development of the rot in poorly drained sites.

  3. Resistant Plants - If a site has been plagued by root rot in the past, plant only species not susceptible to Phytophthora. Even within a genus or species, there may be cultivars that are more or less susceptible to the problem. The fungus stays around in the soil so new, susceptible plants are very likely to acquire the disease too.

Generally the most effective control of this root rot disease is to follow the preventative measures listed above. As a last resort, there are some soil drenching treatments that may be attempted. This is usually more effective in the nursery where the plants are all in separate containers with a small volume of soilless media. In the home landscape, these treatments are usually not very effective.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

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