Root rot is a common problem and can be devastating for gardeners as plants affected by this soil-borne disease can die. Here’s a simple guide to identifying and treating the problem, as well as tips to avoid it. This issue is usually caused by poor drainage combined with overwatering or prolonged wet conditions. It can affect plants both in garden beds and pots, indoors and out.


A Peace Lily or Spathiphyllum in a white ceramic pot against a tiled wall. The plant is drooping with brown, crispy flowers. It is likely suffering from root rot.

Got a plant that looks like this, even though the soil is damp? You might be dealing with root rot.


How to identify root rot

Root rot describes the effect of the disease as plant roots literally rot. The disease is also known as dieback. As root rot is happening out of sight, gardeners need to be aware of above-ground symptoms before the disease has progressed too far to treat. One obvious above-ground symptom is leaves that wilt when the soil or potting mix isn’t dry and the plant doesn’t need water. Stems or trunks may also show signs of splitting or weeping, while growth may also dieback. The soil around the plant may have fungal growth associated with the root rot fungus. As the disease progresses, the plant may lose its roots, become loose in the soil and show signs of dieback (dead leaves and twigs).

The main root rot agents are pythium, armillaria and phytophthora, which are types of fungus. The disease-forming fungal spores are often carried through the soil by the flow of moisture and can also be introduced into new areas of gardens by moving soil around – even on tools and boots.


Left: A close-up of a plant's splitting stem. Right: A close-up of a plant's disintegrating root system. Both are symptoms of root rot.

Splitting stems above ground can be a telltale sign of root rot, while under the surface, roots may be disintegrating, leaving the plant loose in the soil.


How to treat root rot

There are products to treat root rot. Searles Root Rot Systemic Fungicide, which is based on phosphorus acid, is a very useful product to treat root rot. It is applied by watering over the affected plant. It is also used as a preventative when applied to susceptible plants (such as daphne) before the disease takes hold, or used after heavy rain events when root rot may occur. Also treat nearby plants if one plant has root rot.

Where root rot has begun to affect above-ground parts of a plant such as the trunk, the use of Root Rot Systemic Fungicide can also be combined with applications of lime sulphur to the diseased area. Scrape back any rotted material and paint the area with a lime sulphur paste. This method can help treat root rot in fruit trees such as citrus.

For potted plants, especially indoor plants which have been overwatered, repot the plant in fresh premium potting mix, thoroughly removing all the old mix and any diseased roots. When purchasing a potting mix, always look for the red ticks indicating it meets the Australian Standard for premium potting mixes. Apply Root Rot Systemic Fungicide to the re-potted plant following label instructions. Get watering right by only watering when the potting mix has begun to dry out, and never allow plants to stand in water (make sure pots have good drainage holes and empty saucers and cover pots after watering).

Large trees that are affected by root rot such as armillaria may need the attention of a qualified tree surgeon. Treatments may include removing affected trees, root barriers and soil treatment with Trichoderma or fumigation.


Left: A person placing a rubber plant in a black nursery pot and saucer inside an ochre ceramic pot. Right: A close-up of roots that have grown through a pot's drainage holes, which could lead to root rot if not remedied.

To reduce the chances of potted plants developing root rot, keep them in plastic nursery pots and ensure the drainage holes aren't blocked by roots or potting mix clumps.


How to prevent root rot

Root rot is much easier to prevent by good gardening habits than to cure. The best ways to prevent root rot is to supply well-drained growing conditions. In heavy soils (such as poorly drained clay soils), plant susceptible plants (such as many native plants, succulents, daphne, lavender, citrus and some vegetables) into raised beds with free-draining soil. In pots, use good quality potting mix and plant into containers with drainage holes in their base. Elevate pots by standing them on pot feet or bricks to assist with drainage. Regularly check that drainage holes in containers are clear of blockages (such as plant roots) and that water is draining after watering.

Avoid overwatering, especially for potted and indoor plants. Water when the potting mix feels dry to the touch and ensure excess water has drained from the pot. Empty saucers and decorative pots if they hold water.

Plants can be highly susceptible to root rot when heavy rain follows periods of drought. Be aware of garden conditions and be prepared to apply Root Rot Systemic Fungicide as a preventative treatment. If necessary, transplant susceptible plants into containers while soil drainage is improved.