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9 Signs Of Over-Fertilized Plants (+How To Fix It)

Fertilizing is essential for your plants. But if you do not follow the correct fertilization schedule for your plants, it will lead to overfertilization, damaging your plants heavily.

If you overfertilize plants, it can create more problems for your plants. Some common signs of overfertilization include salt accumulation on the soil surface, discoloration of leaves, dry plants, dropping leaves, and so on.

This article will discuss the various benefits of fertilizing plants and the warning signs that your plants show if you overfertilize them.

Indoor plant fertilizer

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Importance of fertilizers

Fertilizers are necessary for plants as they are packed with multiple nutrients that are otherwise not sufficiently available in the soil.

Fertilizers provide plants with macronutrients like Nitrogen, Potassium, and Phosphorous, and micronutrients like Iron, Magnesium, Manganese, Calcium, and many more nutrients that are required for the best growth of plants.

The main nutrients in fertilizers are:

  • Nitrogen encourages foliage growth.
  • Phosphorous increases root growth and flowering.
  • Potassium encourages the plant to absorb other nutrients.

However, it is very important that before using fertilizers in the soil, you know about the correct dosage and instructions to avoid any chances of overfertilization.

What is over-fertilization?

Despite all the benefits fertilizers bring to your plants, you can still cause great harm by overfertilizing the plant.

Overfertilization is detrimental to the health of your plants, and if not checked, it can kill your plants over time.

Under-fertilization is better than overdoing it.

Just like humans, though we need all the vital minerals and nutrients to thrive, if anything goes too high, it can make s fall sick same goes for plants.

Too much fertilizer can make your plants sick.

Overfertilization can reduce the growth of your plants, make them more vulnerable to pests and bugs, and make them dry and kill them.

We will discuss the several signs in more detail below.

The signs of overfertilization are not always very clear, and sometimes it might be similar to other problems.

So, in this article, we will discuss the most common signs, but you also need to check if there is any other problem with the plant.

Causes of overfertilization

Fertilizing indoor plant

Here are a few reasons that lead to overfertilization:

  • Poor drainage of the potting soil also leads to overfertilization.
  • Using an excessive amount of fertilizer at one time.
  • Fertilizing with soluble fertilizers repeatedly without leaching the soil.
  • Incorrect usage of slow-release fertilizer combined with soluble fertilizer.
  • Fertilizing with a slow-release fertilizer in bone-dry soil.
  • Fertilizing during the hot afternoon or very temperatures.
  • Applying fertilizers to the leaves.
  • Applying too close to the seeds or baby plants.

The right way to fertilize

Most houseplants need to be fed in the growing season with a combination of 20-20-20 or 10-10-10 NPK.

Using liquid fertilizer is easier when watering plants.

Flowering plants require you to do more fertilizer than foliage plants before the blooming while the buds are still forming.

Plants in lower-light setups require lesser fertilizers than those growing in bright light.

This is because, in low light, the growth of the plants reduces, so the chances of overfertilization increase.

Plants grow at different rates all year round.

They are most active and thus need more food in the growing season, which is spring and summer.

In winter, they are less active and need lesser nutrients to grow.

This is why most houseplants go into dormancy or their growth increases in winter because the long hours of darkness and the cold are not suitable for most houseplants.

This is why experts always recommend not fertilizing plants after fall.

With the reduction in growth, the plant needs no extra nutrients during this season.

The fertilizers are left unused in the soil resulting in accumulation and root burns.


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What are the harmful side effects of over-fertilization?

Overfertilization causes two main problems in the plant which are:

  • Excessive salt accumulation
  • Nutrient imbalance

Fertilizers have a very high number of salts and different minerals.

So excessive fertilization increases the salinity levels of the soil since salts absorb water.

Too much salt in the soil and the water before it can reach and get absorbed by the roots.

Too much salt sucks up the moisture from the roots leaving them weak and dry, and that process is known as reverse osmosis.

This dehydration of the roots makes the plant get the required amount of moisture, resulting in underwatering and plants developing brown tips and edges.

The primary danger that overfertilization causes are burning the roots.

When the salinity levels increase too much in the soil, the water from the roots begins to flow out, which causes them to burn as water helps to keep them cool.

This makes them begin to dry up, and the plant starts drying.

The roots are mostly affected as they are underground, and the fertilizers reach them more than other parts of the plants.

Signs of over-fertilized plants

When the plants suffer from over-fertilization, it shows several signs of distress.

Some signs are easy to identify, while others can be tricky.

1. The white crust of fertilizers on the surface of the soil

Chinese evergreen soil fungus

One of the most obvious signs of overfertilization is salt accumulation on the salt surface.

The plant is not using the leftover fertilizers, and they begin to accumulate on the surface.

You see them more commonly in potted plants as they look like white crystalline and are coarse to touch, similar to table salts.

2. Yellowing leaves

Monstera yellow leaves

Though yellowing can be a common sign of multiple problems, is overwatering, underwatering, too much or too little light, or plant aging, it can also symbolize overfertilization.

The yellowing mostly starts at the edge of the leaves, and as the situation worsens, it moves inwards and coves the entire leaf.

If you see a similar situation, examine the plant carefully. 

3. Browning of the leaf tips and margins

pothos brown

When the plant has been over-fertilized, the edges or tops begin to turn brown sometimes.

This is because the roots are unable to absorb water and hence are turning brown due to dehydration.

4. Limp, dry brown or black roots

snake plant root bound

This problem symbolizes a root “burning” sign that we spoke about earlier. 

Rotten roots caused by overwatering also become black, but the roots get mushy and smelly.

However, the burnt roots look black, brown, and dehydrated looking.

As they extract water from the roots, they fall dry and limp and turn dead, brown, or black.

5. Leaves dropping

Croton dropping leaves

Defoliation or leaves falling can signify overfertilization.

It can also signify other problems like incorrect watering.

So you should inspect the plants to be sure of the problem that is damaging the plant.

6. Drying out leaves 

Peace Lily dropping

As the condition progresses, the leaves begin to fall off the plant after wilting.

7. Reduced growth rate

All the nutrients must be in the right proportion for the plants to grow right.

If you are not seeing any growth or the growth has suddenly decreased, it might be one of the warning signs of overfertilization.

However, a reduction in growth rate can also be due to reasons like seasonal changes, root rot, and pest infestations.

If you are sure that the plant is not suffering from any other problem, then check for overfertilization.

With water extracted from the roots, the plant suffers from dryness and becomes unable to absorb nutrients and water.

This causes a reduction in the growth speed of the plant.

8. Overgrowth but no signs of flowering

zz plant turn leggy

Overfertilization also leads to leggy growth.

You may notice that the stems are getting longer and leggy, with fewer leaves or no flower growth.

Inadequate lighting may also be another reason for leggy growth, so check the symptoms thoroughly.

9. Wilting 

Boston fern sunburn

The leaves lose water through their leaf cells as the plants begin to dry up.

The leaves gradually begin to lose their rigidity and begin to wilt.

The table below describes the three main nutrients and the signs of their excess accumulation in the soil.

Nutrient Excess
Nitrogen Excess nitrogen produces darker green color in the leaves, and the stems become more rigid. The younger leaves can become yellow as they cannot absorb the other nutrients.
Potassium Excess potassium can lead to deficiency in other nutrients like iron, manganese, zinc, etc. this shows older leaves getting yellow margins along the edges and new leaves turning pale green.
Phosphorous Excessive phosphorous will reduce the absorption of zinc and copper. The leaves begin to show purple or bluish hues, and new leaves show yellowing and become narrow in shape.


How to fix over-fertilized houseplants?

Philodendron watering

If your plants show the above warning signs, you must take the necessary actions.

Do not panic because, though overfertilization can damage your plant if left untreated, if checked, it can be cured easily.

You can follow a few steps to treat the fertilizer burns in your plants.

Begin by clearing the salt buildup by completely stopping fertilization.

It is common to get tempted by the thought of fertilizing the plants if they look unhappy, but this is why overfertilization occurs.

Manual removal

If a layer of salt accumulates on the potting soil surface, you can take a spoon to remove them carefully to prevent it from further mixing with the soil but do not scoop out more than ¼ of the soil.

Removing the affected parts of the plant

Those parts that have already been damaged with burns cannot be reversed, so it is best if they are removed from the soil.

After removing those parts, wait for a few days to see if your plant is still not recovering, then go to the next step.

Leaching

If the plant is still not cured, leach the fertilizer out of the soil with a very long watering.

Let the water drain out, and repeat the process three times.

The salt from the soil gets dissolved in the water and leaches out of the soil.

To do this, bring your potted plant to the sink or balcony and put two bricks below the pot so the water can flow directly out of the drain hole. 

Then pour water to fill the pot and wait 10 minutes to let the salt dissolve in the soil.

Then repeat the process.

This process is natural in outdoor plants as it leaches out salt with the help of rainfall, but for indoor plants, this needs to be done manually. 

After you drain the soil, stop fertilizing the soil for 1-2 months until you see the plant showing signs of recovery.

Flushing

Many people confuse leaching with flushing, but these are two different processes.

In flushing, we add chemicals to the water to dissolve the excess salt more easily and increase the salt removal rate.

Flushing is done by outdoor or larger plant owners and not much by indoor container gardening.

Repotting

snake plant repotting

This is the last and final recovery step if all the above procedures fail to show results.

Though repotting might sound like a good solution, we must remember repotting puts plants under extreme stress, which may be too much for an already stressed plant.

Hence this must be the last resort if all other techniques fail.

Repot in a fresh soil mix that is light and has good drainage.

After repotting, refrain from fertilizing the plant for 2-3 months, as the soil will already have fertilizers while preparing it. 

Tips to prevent overfertilization

Here are a few tips that will help you prevent overfertilization.

  • Ensure you give your plants the right fertilizer in the right proportion. Less is better than using more than the required ratio.
  • Do not fertilize houseplants in winter.
  • Fertilize houseplants only in the growing season when the plants are most active. During this time, they need food and nutrients to grow.
  • Leach the soil every 3-4 months to clear any fertilizer build-up. 
  • Liquid fertilizers are preferred over solid fertilizers as they get distributed more evenly in the soil, while solid fertilizers need more time.
  • Never fertilize in dry soil. Soil should always be moist when you fertilize.
  • Use well-draining soil. Sometimes, if the soil is too compact, the fertilizers do not get flushed out and stay in the soil for too long. 
  • Always read the instruction for usage before fertilizing.
  • Use a good quality pesticide to prevent pest infestations.
  • Refrain from overwatering. Use a moisture meter to ensure you only water when your plants need water.

Source: Indoor Plant CareEffects of Winter Foliar Fertilizing, and Plant Growth PromotersHELPING PLANTS PREPARE FOR WINTER.