You may have heard before that sterilizing soil is an excellent way to kill all the harmful bacteria, weed seeds, insects, viruses, and soil-borne pathogens that can hide in your dirt, waiting to pounce and feed on your poor, unsuspecting house plants.
On the other hand, you might have heard that it’s not a good idea and will kill or harm the beneficial nutrients and microorganisms that live in the soil that plants need to thrive.
So, what’s the best method?
Is sterilizing soil in your microwave a genius hack, or is it just an internet myth that will only leach all the life-giving nutrients out of your soil?
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Should You Sterilize Soil in the Microwave?
It’s completely safe to sterilize soil in the microwave. Put moist soil in a plastic bag or covered container with vents for steam. Microwave on high or until the internal temperature reaches up to a minimum of 180 degrees Fahrenheit. Then, it will be adequately sterilized and ready for planting.
Why Sterilizing Soil in the Microwave’s so Controversial
The question of whether to sterilize soil in the microwave has been hotly debated among gardeners and scientists for a long time.
After all, soil from the ground can contain weed seeds, pests, and diseases.
That’s why many people agree that sterilizing the soil is a good idea because it cleanses the dirt and prevents those harmful things like insects or diseases from gaining access to your plants.
In addition, it ensures that your plants will have clean, safe soil to grow in that will provide optimal conditions.
While it’s always possible to go to the store and buy a sterile potting mix, not everybody has the funds for that.
So instead, you can use your microwave at home to quickly and safely sterilize dirt right from the ground in your yard and then safely use it for planting.
How to Sterilize Soil in the Microwave
To begin, you’re going to need some topsoil from your yard. If you only have a small or medium amount of dirt to sterilize, this method will work perfectly for you.
You’re also going to need a microwave-safe container or a Ziploc sealable plastic bag.
Before you put the soil in the microwave, it’s essential to poke some vent holes in the top of the container or leave a corner of the bag unsealed.
If you don’t, steam will build up and eventually explode, which definitely will make a giant mess in your microwave.
Another critical step is making sure that the soil’s moist. Add enough clean, fresh water so that the dirt will be wet enough to steam in the microwave.
Microwave on High for 90 Second Intervals
For every two or three pounds of soil, you should microwave on high for about 90 seconds.
When it’s done, stick a heat-safe thermometer in the center. It needs to reach 180-200 degrees Fahrenheit to be appropriately sterilized.
You might want to take your microwave out to the garage or have some good ventilation for this task, as it can make an unpleasant smell while it’s sterilizing.
Once it’s reached the appropriate temperature, you’re going to take the bag out of the microwave and leave it closed.
Cover up the vents to prevent the rest of the steam from escaping if you’re not ready to plant right away.
Wait until the soil has cooled off entirely before using it. It’s now sterilized and ready to grow your houseplants or veggies.
Why Do People Sterilize Soil
The decision to sterilize soil has most people divided. Some gardeners and plant enthusiasts swear by the technique, saying it provides a healthy soil base for a plant to thrive in.
Others think it’s a terrible idea and that it kills all the beneficial bacteria and nutrients in the soil that are so integral to the plant’s healthy growth.
While some people may not be proponents of this technique, microwaving soil to sterilize it is a perfectly safe and acceptable method.
In fact, there are many different soil sterilization methods other than microwaving, like using the oven or even the sun.
However, if you’re trying to repot a mature, healthily-growing plant, you may not need to sterilize the soil.
Soil Sterilization is Ideal for Growing Seeds and Young Plants
Sterilization of the soil is ideal for planting small, young, weak, or unhealthy plants, as they can be more susceptible to things like diseases or bacteria because they’re not strong enough to fight it off.
However, sterilization is also kind of like using a broad-spectrum insecticide.
Unfortunately, it can kill the good microorganisms that help the plant transport essential nutrients for efficient absorption and growth.
But, the good benefits of sterilizing soil outweigh the bad, particularly when you’re planting seeds, seedlings, or juvenile plants.
In fact, sterilized soil is perfect for propagating houseplants, which will take root easily in the clean soil and should grow to be healthy and strong.
This Sterilization Technique Provides Benefits
People also sterilize soil in the microwave because it has some great benefits. For one, it’s a cost-effective way 0f getting clean and safe dirt.
It’s also non-toxic, less harmful to the environment than other chemical methods, and helps control the spread of bad bacteria, diseases, or germs.
Also, by killing off the weed seeds ahead of time, you avoid the tedious task of constantly weeding every time new shoots come up.
When to Sterilize Soil
The time to use sterilized soil is right before planting. That way, the plants have safe and clean dirt to thrive in while they grow.
While you might be tempted to repot a mature, healthy plant with sterilized soil, try to avoid this. Its root ball is already well within unsterilized soil, which inevitably causes cross-contamination.
That’s why sterilization is perfect for germinating seeds or transplanting seedlings or young plants.
Remember, immature plants are very vulnerable to damage from insects and pathogens from the soil.
They can also suffer from weed seeds that germinate and then hog all the nutrients in the soil.
This type of sterilization is also effective at killing off nematodes, a common garden pest that can cause an incredible amount of damage in a very short time.
It also helps get rid of bacteria or harmful microorganisms that could cause yellow, curling leaves, nutrient deficiency, and in general, an unhealthy plant.
When it comes to sterilizing soil in the microwave, it’s a perfectly safe technique that can help you get clean, safe soil for your plants to grow in.
However, it’s not ideal for mature or already healthy adult plants that already have a built-up resistance to things in the soil like pathogens or diseases.
For germinating seeds or seedlings, sterilized soil is not only a good idea; it’s necessary to give your young plants a healthy environment in which to thrive and flourish.
You can easily sterilize soil in the microwave using a vented microwave-safe container and some wet soil. Cook it on high for 90-second intervals, and let it cool to room temperature before using it.
So, the verdict is that sterilizing soil in the microwave is a genius hack that’s perfect for saving money on expensive potting soils and keeping your young seedlings big, green, and healthy.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.