Root rot is a condition that, if left untreated, will kill plants. Because the first symptoms of root rot occur beneath the soil, gardeners are often not aware of the problem until it is advanced. When plants start showing symptoms of root rot, such as yellow leaves or stunted growth1, take action immediately to resolve the problem.
Plants in soils too dense for water to drain out efficiently, or in containers that lack sufficient drainage holes, are most susceptible to root rot. While container plants are most at risk, garden plants are not immune to root rot. Most garden root rot issues can be prevented by taking steps to improve soil drainage before planting.2 While it may seem like excessive water is the cause of root rot, the problem starts because too much water provides the perfect environment for the real cause: fungus.
Identifying Root Rot
Root rot can be identified by the presence of soft, brown roots.2 The root system of a healthy plant should be firm and white. But when soil is soggy, fungal spores multiply and the fungus starts to spread3, developing in the extremities of the roots first. As the fungus advances, healthy portions of root turn brown and mushy as the roots die. The plant is then unable to absorb the nutrients it needs, and that deficiency becomes apparent in the condition of plant foliage. Leaves begin to wilt and turn yellow or fall off, growth slows, and blooming may be delayed.1 In the most extreme cases, when conditions are ideal for the fungus to spread quickly, plants can die within 10 days.3 If these symptoms occur in a plant, loosen the soil around the base of the plant with a hand trowel or shovel and remove the plant from the soil. Gently shake the soil from the roots and inspect them for rot.
Dealing with Root Rot
Once root rot is identified, you must determine if the plant can be saved. If the entire root system has already become mushy, it is too late to save the plant. However, if some healthy, white, firm roots exist, try to bring the plant back to good health by replanting in fresh soil with good drainage.
Prepare plants for replanting by cleaning the roots gently under running water and removing all brown, mushy roots with a sharp pair of scissors. Cut the healthy root just above the damaged area. Work quickly to replant within a few hours. After all roots are pruned, sterilize the scissors with a solution of 1 part bleach to 3 parts water4 to avoid spreading fungal spores to other plants or soil.
- Select a container with several small drainage holes or one large drainage hole to ensure that excess water will escape. If you want to reuse the old container, first disinfect it by soaking it in a solution of 1 part bleach to 9 parts water for 30 minutes.3
- Fill the container with 2 parts store-bought soil, 2 parts peat moss and 1 part perlite.5 Never reuse the old, diseased soil, and resist using garden soil, which can contain a number of pathogens.
- Dig a hole in the container soil at least twice the width of the root ball to avoid crowding roots.2 Place the plant in the hole, backfill, and then water thoroughly.
Replanting in Container Plants
In extreme cases of root rot, garden soil may require replacing, but in most situations, improving soil drainage and adding amendments is sufficient to prevent future problems.2 Take the following steps to replant in a garden:
- In the garden space, identify low-lying areas that collect water or soil that slopes toward a building. If necessary, add drainage channels to direct water away from the garden space or regrade soil to ensure that water drains away from garden beds and buildings.2
- To prepare for planting, improve drainage in dense soils by increasing organic material. Add amendments, such as earthworm castings, to help make the nutrients in the soil more available to your plants. In dense soil, add Pennington Fast Acting Gypsum to help loosen compacted soil and to promote healthy root growth.
- Dig a hole twice the width of the root ball, place the plant in the hole, backfill, and then water well.
Avoiding Root Rot
Prevent the reoccurance of root rot with good gardening practices. The following rules apply to garden and container plants in all regions and all seasons:
- Do not overwater. Only water when the soil is dry 1 to 2 inches below the surface of the soil, and use containers with ample drainage holes.
- Give plants plenty of room to grow. Containers that are too small for plant roots can cause drainage issues.2 When plants get too big for their containers, move them to larger pots.
- Make sure plants get enough light. Poor lighting conditions may allow soil to stay too moist.
- Grow new plants in healthy, loose soil, and always add the necessary amendments before planting.
- Fertilize properly. Imbalances in fertilizer can cause symptoms similar to root rot.1 Use a high-quality fertilizer, such as Alaska Fish Fertilizer 5-1-1, plants to promote healthy growth. Apply fertilizer according to label instructions; never over-fertilize.
While root rot is a serious issue for gardeners, treating the problem as soon as symptoms occur greatly increases the chances of saving affected plants. Don't let fungus thrive in soggy soil; instead, provide good drainage and a healthy soil environment in which your plants can thrive.
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- "Fungal Root Rots and Chemical Fungicide Use," Penn State Extension
- Stephen Nameth, Jim Chatfield, "Root Problems in Plants in the Garden and Landscape," Ohio State University Extension Service
- Jill Pokorny, "Root Rot of Houseplants," University of Minnesota Extension, February 2000
- Alicia R. Lamborn, "Disinfecting Pruning Tools," University of Florida Extension
- Bodie Pennisi, "Gardening in Containers," University of Georgia Extension, February 2015