What Causes Root Rot?



Soil
Watering
Pot types
Lighting
Root health
Fertilizing
Symptoms of root rot
Root rot treatment


Root rot is a common worry for plant owners because of how detrimental it can be to the plant. One of the biggest worries we hear from our customers is that they fear they have root rot from over watering their plant.


The most common cause of root rot is a lack of oxygen in the soil from excess moisture. Over time, oxygen pockets are essentially flooded out each time the plant is watered. Without oxygen, roots are not able to breathe and they will eventually die. Once the roots begin dying, fungi take over and begin consuming the roots. Pythium, Phytophthora, Rhizoctonia, and Fusarium are the most common fungi that feed on plant roots. If not caught quick enough, the fungus can spread to the rest of the root system making the survival of the plant unlikely.


Adjusting factors such as the soil type, watering schedule, pot type and sunlight will help reduce the chances of your plant getting root rot.



Soil


Often, plants are sold in a dense potting soil that is designed to hold onto moisture for longer periods of time. The soil is designed this way because the greenhouses where plants are originally grown tend to be very warm environments with a lot of sunlight shining on the plants at all angles. The dense soil reduces the frequency the nursery workers need to water the plants. Since our homes tend to be much cooler environments with lower lighting than plant nurseries, newly purchased plants should be repotted into a coarser soil that provides more air pockets for the roots and can dry out more quickly. You can even make your own soil mixture by adding coarse materials such as perlite, pumice, coco coir or bark to a general purpose potting soil.


Here are some soils options designed for houseplants:



Watering


Over watering a plant often occurs when it is watered on a set schedule instead of first checking the soil moisture before watering again. If your plant’s soil is sopping wet to the point where moisture comes off on your hands when you check the soil, it should be left to dry more before watering again.


When the first few inches of the soil in smaller pots under 8” is dry, the plant can be watered. Larger pots over 8” hold onto a lot more moisture towards the bottom of the pot, so it is recommended that a moisture meter probe is used to determine the moisture level deeper in the pot. The moisture meter should read between ‘moist’ and ‘dry’ before watering again. If the meter reads between ‘moist’ and ‘wet’, push the next watering out further until the soil is below the ‘moist’ mark.


When watering your plant, water thoroughly until moisture runs out the drainage hole. Doing so reduces the frequency you will have to water your plant and it will allow the entire root system of the plant to get moisture. Roots that don’t get sufficient moisture can die off, negatively impacting the health of the plant.



Pot types


Ensuring there is a drainage hole in your pots is an important step in regulating the amount of water your plant receives and in reducing the chances of root rot. If your plant is in a pot without drainage, the chances of over watering your plant increases.


Choosing a pot made out of a porous material such as ceramic or clay can reduce the chances of over watering because excess moisture can be absorbed by the pot material. Plastic pots allow the soil to hold onto moisture for much longer and is best used for water loving plants such as ferns.



Lighting


Plants placed in low light environments in the home are often the most susceptible to root rot. This is because plants take up less moisture with the less sunlight they receive and the soil holds onto moisture for a longer period of time. If your plant’s soil is still very moist after a couple of weeks, you may need to place the plant in a sunnier spot or replace the soil with a better draining type.


During the fall and winter months when the days are shorter and temperatures are cooler you may need to cut back on your watering, especially in cooler regions. Sometimes plants will go dormant or slow their growth when they sense shorter day lengths and will take up less moisture. Plants set back further in the home may need to be placed closer to windows during these months to maximize the amount of light they receive. Grow lights can be purchased to supplement the sunlight or they can be used to light a plant full time if the lighting in your home is insufficient.


Here are some different types of grow lights:



Root Health


A plant’s roots will tell you what the overall health of the plant is. Without a healthy root system, a plant will not thrive. Healthy roots on a plant should be plump and either white or brown in color. The color of the roots can vary depending on the plant type, but they should never be black or mushy. Often, rotting roots and excessively damp soils will have a sulfur smell to them which is caused by an overgrowth of bacteria.


Healthy Roots

Rotten Roots

If your plant’s roots have a fuzzy, mold-like appearance to them, it could be a natural bacteria called mycorrhiza that protects the roots from soil pathogens and helps the roots go in search of water and nutrients. It is important not to apply chemical fungicides to plant roots to avoid killing the mycorrhiza.



Mycorrhiza on Roots


Fertilizing


Fertilizing your plant regularly can help reduce the chance of your plant getting root rot by strengthening its roots and above ground growth. Any balanced fertilizer such as Osmocote ‘Flower & Vegetable’ can be used on most plants to improve growth and the overall health of the plant. Some fertilizers and soils even have mycorrhiza fungi added in to enhance root health.



Symptoms of root rot


  • Wilted foliage even though the soil is moist

  • New leaves come out discolored or stunted

  • Die back of complete stems

  • Mushy stems

  • Black/brown lesions near leaf center vein

  • Stunted growth

  • Yellow leaves

  • Leaf drop



Root rot treatment


If root rot is caught early and there are still some healthy roots, there are measures that can be taken to save the plant. Luckily, roots are the fastest growing part of a plant and they can regenerate from damage or disease given the right conditions.


If your plant begins showing signs of root rot, it is best to immediately check the roots to determine their health. If it is determined that your plant has root rot, but there are still some healthy roots, follow these steps to remediate the spread of the disease:


Step 1: Cut away any mushy, black roots with scissors or pruners cleaned with bleach or rubbing alcohol.


Step 2: Clean as much of the soil off of the roots with clean water.


Step 3: Dispose of the soil the plant was potted in.


Step 4: Sterilize the pot with bleach or rubbing alcohol.


Step 5: Replant the plant into fresh soil.


Step 6: Water in the plant normally. You may need to water twice if the new soil does not immediately become absorbent.


Step 6: Fertilize with an all purpose fertilizer or one designed for your specific plant type.



If you take these care instructions to create a healthy living environment for your plant’s roots, you can reduce the chances of root rot and increase your plant’s chances of becoming a lush, hardy houseplant.



If you have any questions about root rot or think your plant may have it, we will be happy to assist you in a virtual telehealth appointment with one of our Plant Specialists. Please click on one of the options below to book an appointment.







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