Discovering root rot is never an enjoyable experience. Even if you find it early enough to save your plant, you still must go through the tasks of unpotting and repotting it. Yet, can you make it easier on yourself and reuse the soil once the diseased parts of the plant are removed?
You can reuse soil that has root rot after thorough sterilization. Still, depending on the type of root rot, many recommend discarding tainted soil, as sterilization isn’t always effective against some fungi. If fungi remain in the soil, plants will likely get infected again.
In this post, we’ll explain why it’s typically best not to reuse soil that has root rot. We’ll also provide three easy, chemical-free ways of sterilizing soil for reuse.
Reasons Not to Reuse Soil That Has Root Rot
Root rot is a common and deadly plant disease that most often results from poorly drained, waterlogged soil. Also known in some gardening circles as soil fungus, it can develop in any plant, indoors or outdoors, though potted plants tend to be the most susceptible.
Fungi or Molds Can Live and Spread Through Soil
Many plant and gardening care guides explain that if you identify root rot on a plant soon enough, you can save the plant. Yet, one crucial step in rescuing a plant from root rot is to replace the tainted soil with fresh soil.
Knowing this, it stands to reason that you should probably discard soil used for plants infected with root rot. Notably, many green thumbs agree with this line of logic.
Common sense isn’t the only defender of this conclusion, as agricultural and horticultural experts also agree. It’s well known in these communities that various fungi or molds are the most common cause of root rot, and the spores of those fungi can continue to live in the soil forever. They can then spread and infect the roots of other plants.
Phytophthora Root Rot Is Difficult to Combat
Phytophthora root rot is a common strain that develops in plants. Translated from Greek, Phytophthora means “plant destroyer.”
Any species of this fungi genus attacks without warning, causing rapid destruction and killing plants quickly. Once these mold spores are in the soil, they can lie dormant for a long time.
Thus, if you reuse soil from a plant infected with root rot, mold spores are still present, ready, and waiting for the right conditions to jump back into action. Should you accidentally overwater at any time, the fungi will be “reactivated” and begin to destroy your plant’s roots.
What’s worse is that the experts studying Phytophthora root rot now believe that these fungi cannot be counteracted as previously thought. The issue may require alternative solutions than those for similar plant diseases and will otherwise continue to be a problem, regardless of our efforts. In other words, the plant destroyer is here to stay.
For these reasons, it’s best to err on the side of caution and discard soil that has root rot and replace it with fresh soil.
Sterilize Soil Before Reusing It
While it isn’t generally recommended, it’s possible to sterilize soil to eliminate root rot-causing molds. However, whether or not this is effective depends on the type of root rot your plant developed and how much of the soil is infested.
For instance, if you discovered non-phytophthora root rot on a plant potted in a large container (and the roots weren’t cramped up along the sides), you may have a good chance of successfully sterilizing and reusing the soil.
On the other hand, if the plant was in a smaller pot with very little soil or had a phytophthora root rot, any efforts to sterilize will likely be in vain.
Keep in mind that any sterilization process will inevitably kill off some good bacteria and organisms along with the bad, leaving behind soil that is disease-free yet also lacking in nutrients. So, while the soil is no longer harmful to your plants, it’s not exactly beneficial, either.
To truly make your previously diseased soil reusable, you should create a 50/50 mix of old, sterilized soil and new fresh soil for your plants.
Note: Avoid reusing sterilized soil with peat moss or any non-aerating substrate, as this raises the risk of root rot returning.
Avoid Using Fungicides
The best sterilization methods for getting rid of the fungi that cause root rot are boiling water, steam, or solarization.
Some guides and gardeners may suggest using natural or chemical fungicides to spray or otherwise apply onto your soil to kill the harmful bacteria. However, more often than not, these solutions only result in different problems, such as pH imbalances, and are best avoided.
Unfortunately, large amounts of infected soil (for instance, a garden in your yard) may require you to purchase a commercial fungicidal drench to help lower the number of spores and return the soil to usable condition.
Easy Ways to Naturally Sterilize Soil That Has Root Rot
Typically, the easiest way to sterilize smaller amounts of soil used for indoor potting containers involves using boiling water or a steamer. Larger outdoor areas of contaminated soil are more easily sterilized using solarization.
Before you begin any sterilization method, ensure you’ve removed all traces of the diseased roots and infected plant material from the soil. Also, take some time to till the soil, stirring it and breaking up any large clumps.
Caution: Those with sensitive health conditions, such as asthma, may wish to avoid handling soil with root rot, as the fungal spores may cause respiratory symptoms.
1. Boiling Water
Boiling water is one of the fastest soil sterilization methods. Simply boil water and then pour it over the infected soil.
You can drain the water through the new pot you’re going to plant in or soak the soil in a large pot or mixing bowl. Allow plenty of time for the soil to cool before using it for planting.
To effectively kill pathogens in the soil, the water must be at least 140 °F (60 °C). You may wish to use a thermometer to verify that you have reached this temperature.
For an example of how this is done, check out this quick YouTube video:
2. Steam
Steam is just as effective and easy a method for sterilizing soil as boiling water. In fact, soil steaming is a technique commonly used in farming.
You can use steaming methods and equipment from your kitchen to sterilize your soil, or you can use a steamer. If you use a steamer, be sure to fill it up with enough water to steam continuously for 15 minutes, so you can thoroughly sterilize a whole pot of soil in a single sitting.
3. Solarization
Like the other methods, solarization is an easy and effective way to sterilize the soil, yet it takes much longer.
After cleaning and tilling your soil, follow these steps for sterilization:
- Add enough water to get all of the soil wet. You’ll want to reach 1-2 feet (0.3-0.6 m) depth for outdoor gardens.
- Use a transparent plastic sheet or tarp to cover the wet soil. To ensure the plastic stays in place, tape sheets onto large pots or use rocks to hold down tarps over garden beds.
- Once the soil is covered, just walk away! Don’t worry about checking on it immediately; it can take 1-2 months for the sun to kill off bacteria in the soil.
Keep in mind that if you sterilize the soil for large outdoor areas, it’s best to give the land a chance to rest and recuperate before you replant. In extreme cases, you may want to wait as long as one year before putting new life into the soil.
Final Thoughts
Soil with root rot can be reused if properly sterilized, but it’s not often worth the trouble. If you were fortunate enough to find root rot in time to save your plant, then perhaps it’s best not to push your luck. The preferred course of action is to put the plant into fresh soil and avoid the risk of the plant catching the disease again.
