Are you worried that your plants are over-fertilized? Here are the common signs of over-fertilization and how to save your plants if that happens.
We all want our potted plants or vegetables in the garden to proliferate and produce plenty of fruits or flowers, so we often use fertilizers to speed up the process. Although the correct usage of the right fertilizer should not harm the plants, fertilizers are often used improperly or excessively.
Just as common mistakes like overwatering or underwatering, over-fertilization is one of the most frequently occurring problems in plants care. This condition often happens either due to the wrong quantity of fertilizer or due to the frequency of its application.
There are already countless brands and varieties of fertilizers, and more seem to emerge overnight. We can find liquid fertilizers, granules, spikes, water-soluble powders, etc. We can further classify these based on their action into slow-release or fast-release fertilizers, organic or inorganic, foliar, soil amendments, and so on.
The variety of these products is overwhelming, and you can easily get carried away when you have to choose a fertilizer for your beloved plants. Hence, many want to try them all and eventually end up choking their plants with these products.
Over-fertilization is a common problem both in potted and outside plants. Yet, it occurs more often in potted plants due to the limited amount of soil.
Signs Of Over-Fertilized Plants
When a plant is over-fertilized, several signs will occur. Unfortunately, many of them can easily be confused with other plant problems, such as over-watering, under-watering, lack of light, or other common problems.
1) White Layer Forming On Soil’s Surface
Fertilizers are mostly a mixture of salts. The majority of the elements are water-soluble; hence they spread quickly in the soil once you apply the fertilizers.
In most cases, when we use fertilizers correctly, we will not see any visible signs on the ground. However, when we use them excessively and the soil dries, the concentrated salts will often create a white crust on the soil’s surface. This can also be observed as a white line at the soil’s level on clay pots or on the bottom of the container, around the water drainage holes. In large concentrations, these salts can even accumulate on the roots of plants, leading in time to the plant’s suffocation.
The presence of a white layer on the soil’s surface could be one of the most obvious signs that you use fertilizer too often or in too large amounts.
However, over-fertilization is not the only possible cause for these white deposits. Pretty frequently, they are also produced by the be minerals from water. While tap water is usually filtered and the amounts of minerals in its concentration are reduced to lower values unto reaching the consumer, water from wells frequently contains high levels of dissolved minerals like calcium and magnesium. This is typically identified as “hard water.”
While calcium and magnesium are considered plants’ essential nutrients and are beneficial in moderate amounts (ideally between 100 to 150 mg/L), in high quantities, just like in the case of over-fertilization, they can become harmful.
In conclusion, hard water will also lead to the formation of white layers at the soil’s surface or on pots, similar to the ones caused by excessive fertilization.
2) Excessive Foliage Growth With Little Flower Or Fruit Production
Another effect of over-fertilization or the wrong choice of fertilizer for a particular plant type can lead to the excessive growth of its foliage followed by the poor production of flowers or fruits.
Contrary to popular beliefs, excessive growth of a plant’s foliage is not necessarily a sign of thriving.
Due to the large amounts of nutrients, the plant grows forcibly and very quickly at first. However, it does not have time to develop a strong root system to support the plant’s needs. Weak roots won’t manage to absorb enough water and nutrients to support fruit-bearing and flower production.
In general, using an unsuitable fertilizer for a specific type of plant may be responsible for this condition.
A widespread mistake is to choose the fertilizer without taking into account its N-P-K ratio. These values should be displayed on the package of each product and represents the concentration of the three essential nutrients for plant growth: nitrogen (N), phosphorus (P), and potassium (K).
A fertilizer that contains a higher concentration of a particular element may be good for some plants but may not produce the desired effects on others. For instance, an unbalanced fertilizer with a high nitrogen (N) concentration may produce excellent results for getting greener lawns. Still, it may not be the best choice for promoting blooming in flowers, as these need phosphorous (P) rich fertilizers.
Different types of plants have different requirements regarding the need for certain nutrients. These needs may even change depending on the stage of development of the plant.
If you always use the same fertilizer that has a certain element in abundance but a very low concentration of the others, it can also lead to over-fertilization.
Although excessive foliage growth with little flower or fruit production is a symptom that can be associated with other plant problems as well, such as the lack of pollination or absence of light, it is frequently a sign of over-fertilization.
3) Leaf Yellowing Or Browning
The yellowing of leaves on plants is not necessarily a sign of too much fertilizer. As shown in another article, there are many reasons for the yellowing of leaves in plants, ranging from natural causes to fungal diseases.
However, when the leaves of a plant that was apparently healthy until recently suddenly turn yellow, you should not rule out the possibility that it may have been over-fertilized, especially if this condition is accompanied by other symptoms described in this article, such as the formation of a white layer on the soil surface or the growth of the foliage with a low yield of flowers or fruits.
Among others, yellowing or wilting of the leaves at the base of the plants can be one of the early signs to indicate the improper use of fertilizers.
4) Slow Or Stunted Growth
Although in some cases of over-fertilization, the plant responds through an excessive growth of its foliage, in others, over-fertilization slows down the development of the plant or even stops it entirely.
Applied too frequently or in the wrong dosage, the fertilizer will lead to the accumulation of too many mineral salts in the soil, and as their concentration increases, it will be more and more difficult for the plant to absorb the amount of water needed. This will automatically slow down its growth or even kill the plant.
Many factors lead to leaf fall on plants during the season when they should still be in vegetation. Among the most common are diseases, various pests, improper irrigation, but also too frequent feeding with fertilizer.
When caused by over-fertilization, defoliation is usually the stage following the yellowing or browning of the leaves. The foliage first changes color and then starts to fall off gradually.
When a plant loses the majority or all its leaves, it may be a sign of root damage, and, likely, you will not be able to save the plant.
How Does Over-Fertilization Affect Plants?
Many do not pay enough attention to how much fertilizer they use because they think plants will take only the quantity of nutrients they need from the soil. Although it seems logical, things do not work this way.
Most fertilizers are made of elements that are salts from a chemical standpoint. Once these get in the soil and dissolve, the salt concentration increases, leading to adverse effects for plants when the levels rise excessively (source).
Among the harmful effects of over-fertilization, we can find changes in soil’s pH, deprivation of the plant of sufficient water due to high soil salinity, root damage, slow plant growth, and so on.
Basically, in excessive amounts, fertilizers will become toxic for plants.
How To Save Over-Fertilized Plants
Over-fertilization can cause severe damage to a plant and can even lead to its death. Still, if the problem is detected in time, you can save most plants.
The effects of over-fertilization are easier to reverse in potted plants than those grown in the garden. However, the advantage of those grown directly in the outside soil is that they require a much larger amount of fertilizer before they are affected by excessive fertilization.
When you realize that a plant is stressed due to too much fertilizer, obviously, the first thing you need to do is to stop adding even more fertilizer. Remove any fertilizer spikes from the soil or any granules that haven’t been yet dissolved by water.
As mentioned earlier, overfertilization leads to excessive accumulation of mineral salts in the soil. Hence, to save a potted plant, one option would be to replant it in another container with fresh soil. However, replanting is not always the best solution because this process itself causes a lot of stress to the plant. Being already weakened, there is a good chance that it won’t recover after a transplant. Also, there may even be salt deposits on the plant’s roots, which will be transferred to the new container.
Another less stressful approach when it comes to attempting to save over-fertilized potted plants is through a process called “leaching.”
Leaching involves rinsing the soil with enough water to clean all the salt deposits formed in the soil and around the plant’s roots.
Therefore, you must first make sure that the drainage holes on the bottom of the pot are not blocked and allow water to drain freely.
Fill a bowl with water and leave it at room temperature for a while. If the water is a little warm, it will favor the dissolution of salt deposits in the soil. However, you don’t want it to be too hot to hurt the plant.
You should avoid any hard water source, as it contains minerals that will, in turn, be stored in the soil. Your goal is to wash away the existing salts, not to add new ones.
Place the pot’s bottom into the sink, bathtub, or in a large vessel. If you have the possibility, it’s probably better to perform this operation outside, so you don’t make a mess.
Pour the water slowly into the plant’s container and lift it to facilitate the drainage. Use a volume of water at least 3-4 times the size of the pot.
The water will drain faster or slower from the containers depending on the soil type, so you will need to be patient.
You can repeat the process as many times as needed. As long as it drains from the pot, the water will not harm the plant.
After leaching, usually, the plant will need some recovery time before regaining its functions and expect new growth or blooms. It is recommended not to apply fertilizer again for a period of at least 30 days because the plant already has enough reserves.
When it comes to saving a plant established directly in the garden, things get more complicated as they don’t have a container to wash away the excess minerals from.
The only way is to stop feeding them fertilizer and just give these plants plenty of water.
How To Avoid Over-Fertilization?
There isn’t a general rule of thumb regarding how often you should fertilize plants or the amount of fertilizer you should apply. Not all fertilizers are created equal, and not all plants have the exact fertilization requirements.
The best way to avoid over-fertilization and make sure you apply the fertilizer properly is to read the label of the chosen product and follow precisely the usage instructions recommended by the manufacturer. Choosing the right fertilizer for a particular plant type is also essential as different plant species have distinct fertilization requirements.
Plants are often classified as heavy feeders or light feeders (source).
The plants that fall into the heavy-feeders category will need more frequent fertilization, while the light-feeders don’t require as many nutrients so that they will need less fertilizer.
Examples of heavy-feeders:
Examples of light-feeders:
Additionally, there is also a third classification of soil-building plants. These include species like beans, peas, clover, and lucerne. Not only that these plants can thrive in nutrient-poor soils, but they also enhance the soil’s quality for the next crop.
It is also essential to choose the right fertilizer for each type of plant. Each fertilizer has an N-P-K ratio on the label. This represents the proportions of the three essential nutrients needed for each plant growth:
- N (Nitrogen)
- P (Phosphorus)
- K (Potassium).
While many plants may grow well with balanced multi-purpose fertilizers, some may have higher requirements of particular nutrients.
For instance, some plants need a higher concentration of nitrogen (plants like tomatoes, cucumbers, peppers, squash, etc.), while others may need extra potassium (lawn grass, roses, soybean, strawberry, etc.). That’s why there are many plant-specific fertilizers, like orchid fertilizer, lawn fertilizer, fertilizers for flowering plants, and so on.
Read this article if you want to learn more about the NPK ratio of fertilizers and how to choose the right product based on this ratio.
Another aspect to consider is that some plants will need more fertilization during flowering or fruit production. Thus, the frequency of fertilizer application may also vary depending on the period of plant development.
Briefly, to avoid excessive fertilization, it is necessary first to know the type of plant and its fertilization requirements. Based on this information, you can then choose the best fertilizer for your plants.