“If a portion of a redwood is rotting, the redwood will send roots into its own form and draw nutrients out of itself as it falls apart.” — Richard Preston

Root rot is one of the most discouraging events in a gardener’s journey. It happens to all of us, and when I inherited a 100-year-old garden, I learned many lessons the hard way, including how to prevent and treat root rot in my plants. This is my full guide on root rot and how to keep your plants healthy. This guide is for everyone, even beginner gardeners. Please leave any comments or questions, and I will be happy to help.

What Causes Root Rot

Water Molds

Oomycetes are pathogens that attack roots by releasing spores (zoospores), which swim toward the host plant and create infections. They will absorb its nutrients, which breaks down the plant’s tissue. Pythium and Phytophthora are considered water molds that cause a majority of these infections. Many water molds are saprotrophic, which means they live on dead or decaying organic matter. This is a critical reason you should be careful to keep your tools clean and your soil in good health.

Fungi

Rhizoctonia Soloni and Fusarium are common causes of fungal root rot. These fungi colonize root tissue, causing nutrient and water blockage. Again, waterlogged soil is a common cofactor. Lack of oxygen in waterlogged soil reduces 02 and creates a weakened plant, which makes it easier for infectious pathogens to attack the plant. Certain fungi produce toxins that break down the root tissues themselves. Yellowing foliage, known as chlorosis, and roots that appear discolored (black or brown) and mushy are obvious signs of infection.

Overwatering

Overwatering creates conditions for pathogens to take advantage of the plant. Just like humans, plants need oxygen to survive. Plants breathe through pores on their roots and leaves. In this context, roots have small hairs used to absorb oxygen. In soil, you need air pockets to allow this respiration to take place. If the pockets are full of water, the roots will ‘drown’.

Bacteria

Often, entering through wounds in the plant, bacteria such as Erwinia and Xanthomonas decompose roots. They also thrive in anaerobic environments, which is why keeping your plant from becoming waterlogged is critical.

How to Prevent Root Rot

Sterile Potting Mix

One of the best ways to start with peace of mind is to get a sterile potting mix. Another option is to sterilize your soil yourself. It needs to reach an internal temperature of 180 degrees but do not surpass 200 degrees. This can be done in an oven and may seem extreme, but it will kill the causative agents that could attack your plant.

Watering Intuitively

Generally, you should not stick to a strict watering schedule. Instead, wait for the top 1-2 inches of soil to dry out before watering. You do want to ensure all of the plants’ roots receive water so they do not dry out, which can also cause dry rot. The bottom line is to ensure you allow for optimal drainage. By sticking your finger in the soil, you can see if any soil sticks to your finger; if so, that likely means the soil is still wet and does not currently need another watering.

Choose the Right Pot

You need to find a pot with drainage holes. This is the first step in creating a happy environment for your plant’s roots. Terracotta pots are also useful for enhancing air circulation and soil drying. I have also discovered ventilated pots, which have small holes to allow air into the root system. I have a problem with choosing overly large pots, hoping my plants will ‘grow into them’. However, this is the perfect disaster as too much excess soil will hold on to water and increase the possibility of root rot.

Bottom Watering

My favorite form of watering is watering from the bottom of a plant. The best practice for watering plants is to primarily bottom water and allow for drainage; don’t let your plant sit in stagnant basin water. Top watering should be done less frequently (monthly) to flush accumulated fertilizer salts. I love my self-watering planter pot for my tomatoes. As of now, as long as I keep my plants outside in the sun, this setup works perfectly, and I have never had faster plant growth. And so far, no root rot! Be aware that just like human illnesses, these plant infections are transmissible, so be sure not to share water between the plants when possible to reduce transmission.

How to Treat Active Root Rot

Remove the Plant from the Infected Area

Remove the plant if you can, from the infected area or pot. Take a look at the roots and see if you can smell the rot, or see any black or brown (discolored) roots. Often, the outer cortex of the plant’s roots is affected, causing them to have a squishy feel. If you can confirm root rot has set in its time to wash & prune.

Using room temperature water, wash off the roots to prepare for the pruning. Use a sterilized pruning shears to cut above the affected area to ensure all the rot is removed. Now after your plant has been pruned you can create your fungicide mixture and set your plant inside as per the directions of your brand.

Finally, you can repot your plant. I recommend discarding the old soil as its possible spores are still inside the soil and will come back for your plant. You can sterilize your soil, but for me, I have more peace of mind starting with fresh soil and repotting. If you want to reuse the pot, you can wash it with hydrogen peroxide, which is also how I sterilize my pruning shears. This will give you a fresh start and hopefully save your plant. At this point, you can apply the fungicide again to the new soil and help prevent future rot.

Fungicides

Use a systemic fungicide to treat the root rot, these spread into the plant when absorbed by the roots and will treat the infection throughout the whole plant. You can find long-lasting ones that keep working for weeks. You can use a soil drench to apply a fungicide to ensure the application reaches the roots of the plant. There are different fungicides for different types of foliage. You can even look into more natural options, including neem oil, sulfur, and baking soda.

Aeration amendments

Since anoxic (oxygen-deprived) conditions are the main environmental catalyst for root rot, you can use aeration amendments to improve the soil structure. You want to increase the oxygen and drainage with materials like perlite (volcanic glass), pumice (porous rock), or wood chips. You can find potting soil made specifically to combat root rot that includes mixes of these elements.

Microbes

Beneficial microbes are ‘good bacteria’ that colonize root surfaces and feed on pathogenic fungi. They also release their own antibiotics. You can find these for sale on their own (which is so interesting to me) and also in root cleaners and soil amendments.

Pots and Products

There are air-pots that are designed to enhance oxygen flow to the plant’s roots. They come in many shapes and sizes and can keep the soil from going bad as quickly. There are also fabric grow bags, which are made from non-woven fabric. These pots allow the roots to grow through them, which prevents root circling and improves root health. I like using aeration sticks (essentially ventilation stakes), which go into the soil and allow oxygen into deeper root areas. If you don’t want to buy these, you can also just use chopsticks to create holes in the soil.

I hope you learned what you needed from this article to help your garden become a stronger and more beautiful version of itself. Please do further research in the particular species of plant you own to give it the best chance for a healthy new start. I hope you have an amazing day, go and enjoy the outdoors!