Can Compost Tea Burn Plants? Here's Everything You Need to Know

Compost tea is an excellent way to provide plants with nutrients and beneficial microbes to improve soil health and help your plants thrive, but does it cause damage to plants, and specifically, can it burn plants? No, it does not, and here’s everything you need to know.

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Can Compost Tea Burn Plants?

Compost tea that is made with high-quality compost (also referred to as tea-grade compost) will not burn your plants. Compost tea is a gentle “fertilizer” that contains small amounts of soluble nutrients, trace minerals, and high amounts of microbial diversity, all of which come from the compost and other inputs used to make the tea.

The microbes in the soil unlock nutrients that are in the soil and then make them available to the plants for them to uptake. This is a natural cycle of the soil that we can support by using microbial-rich soil amendments such as compost tea.

With high-quality teas, you can feed your plants much more often than conventional fertilizer without having to worry about burning them.

Are There Times When Compost Tea Will Burn Plants?

While it is very rare that compost tea can potentially burn or damage plants, it’s important to remember that if the compost tea is not properly aerated during the brewing process, it can contain harmful microbes such as E. coli and salmonella, which will damage plants.

Additionally, if the compost tea is made from compost that did not reach high enough temperatures during composting, it may contain harmful microbes that can negatively impact plants when the compost tea is applied, therefore, it is essential to use proper brewing techniques and the right types of compost for compost tea. This can happen, but usually, there is a low chance!

How to Tell if Compost Tea Burns

Before applying compost tea, there are a few ways to tell if it's likely to burn your plants:

1. Look at the Color of the Compost Tea

The compost tea should be of a dark brown color, indicating that the compost has been fully extracted of microbes and minerals. If the compost tea has a lighter color, this is a sign of less brewing time. Inactive and unbalanced microbes are not harmful.

2. If the Tea Contains Pathogens

There are a number of ways to tell if compost tea contains pathogens:

• If you experience a foul smell coming from the compost tea, for example, it smells like rotten eggs, this could indicate that it potentially contains pathogens and that it has gone anaerobic. Properly aerated compost tea should not smell bad.
• If the compost tea was made from compost that did not reach high enough temperatures may mean it contains harmful bacteria.
• Compost tea made from animal waste or fresh manure is more likely to contain foodborne pathogens, and this is because animal feces can harbor bacteria that cause illness. Typically, compost made from plant materials does not contain the same risk.

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How to Fix Plants Burned by Compost Tea

Although it’s a very rare occurrence, but If you have accidentally burned your plants with compost tea, there are a few key steps that you should follow:

• Immediately stop applying the compost tea and switch to using plain water.
• Prune off any damaged or dead leaves and foliage to allow the plant to focus its energy on new growth.
• Pay close attention to the plant and ensure it is in optimal growing conditions, such as the right volume of water, sunlight, etc., so it recovers.

What Are the Best Practices for Using Compost Tea on Outdoor Plants?

When you are looking at using compost tea, it's about making sure that you pay particular attention to the following practices:

• Use high-quality, properly aerated compost tea, and avoid compost tea made with too many additional nutrients, as this can result in an overgrowth of harmful microbes.
• Ensure the compost is fully mature and has reached high enough temperatures so it can kill the pathogens.
• Apply at the right frequency and concentration, but if you are making it with the correct measurements, you do not have to dilute compost tea.
• Time the applications properly. The best times to apply compost tea tend to be when the plants and soil are moist, as this helps the microbes to stay active, which tends to be in the evening. While many people recommend spraying in the morning, this is actually not the best because the sun burns the tea off the plants before it can be absorbed by the plant. Likewise, you should avoid applying it in the heat of the day for the same reason.

• Monitor plants closely after the application and watch for any signs of stress or burning on the plants. If there are any issues, adjust the concentration or the frequency.
• Do not use it as a spray, but instead, applying it as a soil drench is more effective because it directly introduces the microbes and nutrients into the soil. Plants absorb nutrients on their surfaces as well as microbial communities living on them meaning that compost tea can provide nutrients and microbes to the roots and the rhizosphere (which is the soil around the roots).
  When applying soil drenches, place the tea around the base of the plant out to the drip line, and for foliar applications, spray until the leaves are thoroughly covered, and be sure to do it during overcast days. Foliar applications are beneficial as many microbial communities live on the plant surfaces and the stomata of the leaves allow nutrients to pass through.

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Compost tea is not able to burn plants because, by its very nature, it is a diluted extract of compost which contains a diverse population of beneficial microbes and nutrients in a gentle organic form, making it easy for plants to absorb without causing burning.

Compost tea made from high-quality properly cured compost is far less likely to contain high levels of nutrients that could potentially burn plants.

While compost tea is not necessarily able to burn plants because of its gentle nature, it's essential to ensure that you have high-quality compost tea and avoid traditional fertilizer because it is chemical-based while compost tea is carbon-based and is feeding the soil for years to come!

The best way to do this is by purchasing compost tea from suppliers that focus on delivering the very best compost tea solutions for plants or making your own!