Root rot is a serious plant ailment that can quickly lead to plant death. Affecting both houseplants and garden plants, understanding, identifying, treating, and preventing root rot is essential for plant health.
What is Root Rot and Why It Happens
Root rot occurs when a plant’s roots decay from lack of oxygen in the soil, often worsened by fungal or bacterial pathogens. Healthy roots need oxygen for respiration and growth. Waterlogged soil cuts off oxygen, creating an anaerobic environment where roots die.
Overwatering is the primary cause, as consistently wet soil deprives roots of oxygen. Poor drainage, such as heavy soil or pots without holes, also contributes. Potting mixes that retain too much moisture can worsen the issue. In these wet, oxygen-deprived conditions, harmful organisms like Pythium, Phytophthora, Fusarium, and Rhizoctonia thrive, attacking compromised roots and accelerating decay.
Recognizing Root Rot Symptoms
Identifying root rot involves observing the plant’s visible parts and its roots directly. Above-ground symptoms often appear after root decay is advanced. The plant may wilt, even in moist soil, because damaged roots cannot absorb water. Leaves frequently turn yellow, especially lower ones, followed by browning and premature drop.
Other signs include stunted growth, a general decline, or a musty smell from the soil. For a definitive diagnosis, gently remove the plant and inspect the roots. Healthy roots are firm, white, or tan. Rotted roots appear dark brown or black, feel soft and mushy, and may easily fall apart.
Treating Root Rot
Treating root rot requires prompt action to improve the plant’s chance of recovery. Carefully remove the plant from its pot, gently loosening and removing old soil from the root ball. Rinse roots under lukewarm water to wash away contaminated soil and view damage. Prune away all soft, mushy, or discolored roots using sterilized scissors, cutting back to healthy tissue.
If reusing the pot, disinfect it with a 1:9 bleach-to-water solution to eliminate pathogens. Repot the plant into a new or disinfected pot using fresh, well-draining potting mix. After repotting, water lightly to settle the soil. Allow the top few inches of soil to dry before the next watering to prevent recurrence. Place the recovering plant in indirect light and stable temperatures to minimize stress.
Preventing Root Rot
Proactive measures prevent root rot and maintain plant health. Proper watering is important: always check soil moisture by inserting your finger one to two inches into the potting mix. Water only when the soil feels dry, and thoroughly until excess water drains from the pot bottom. Ensure no standing water remains in the saucer, as this causes waterlogging.
Excellent drainage is another important preventative step. All pots must have drainage holes. Use a well-draining potting mix, often with perlite or bark, to prevent compaction and promote aeration. Selecting the right pot size is beneficial, as an overly large pot holds excessive moisture. Good air circulation helps the soil surface dry efficiently. Finally, avoid over-fertilizing; excess salts can damage roots, making them more susceptible to decay.