Excess and deficiency of boron can cause severe issues for your plants. If you want to keep your plants healthy, then you should know where the fine line between too little and too much boron is. – Gro Indoor
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Everything you need to know about boron and its importance for plants

by 09 Apr 2023

Everything you need to know about boron and its importance for plants

Like many others essential components, boron is also a micronutrient essential for the healthy growth and development of plants. But plants do not need it in excessive quantities and require only a small amount. The role of boron in plant growth is still under research, and there is a lot that we still need to learn about it.

Boron, in both soil and hydroponic grow systems, is taken up from the root system. In the case of foliar spray application, it is absorbed through the leaves. As a grower, you should immediately take steps to supplement plants with additional boron if you notice a boron deficiency.

How to Use Boron in Plants?

Boron is vital for plant growth, and a boron deficiency can cause some severe growth-related problems in plants. When a plant lacks other nutrients, the most prominent sign of a deficiency is leaf yellowing; however, this is not the case if plants have a boron deficiency. At the same time, symptoms of boron toxicity are similar to that of other nutrients.

Boron and calcium work hand in hand to ensure proper cell wall synthesis in plants. It also helps in creating new plant cells through cell division. Apart from this, it also helps plants with their reproduction process aiding in seed and fruit development as well as pollination.

This isn’t it. Boron’s applications are way more than what we have already talked about. Other important functions of boron include metabolizing nitrogen, transporting carbs and sugar, and forming various proteins. It also regulates hormones and transports potassium to the plant’s stomata. While the last function seems unnecessary, the reality is pretty different potassium helps plants maintain water in the cells. If the cells do not have adequate water levels, they lead to the plants weakening and ultimately dying.

We are not done yet. Boron is also responsible for transporting sugars, and a lack of boron means fewer exudates and sugars in the plant's roots. Lack of sugar means difficulty in colonization for mycorrhizal fungi this is something that isn’t given much importance, but it is very important for your plant’s healthy growth and development.

What are Good Sources of Boron?

If you notice that your plants are facing a boron deficiency, then one of the most preferred methods of dealing with it is using a micronutrient fertilizer. If soil is lacking in boron, it likely lacks other nutrients too.

If you feel that it is only the boron lacking, a boron supplement is what you need. But you need to be extremely cautious as overapplying a boron supplement is extremely common. Other solutions include using borax and boric acid.

You can make a foliar spray using ½ tablespoon of boric acid per gallon of water. But be very careful when applying it as extra boron can end up being harmful to your plants. If you are someone who is growing crops like cabbages, pears, apples, or broccoli, a good annual prophylactic measure is to use a light boron spray.

Boron deficiency in plants

Plants generally do not suffer from boron deficiencies alone. If your plant is suffering from a boron deficiency, it is highly likely that the plant is also suffering from a calcium deficiency. If you want to avoid these deficiencies, you should water your plants adequately.

Boron also increases root uptake of phosphorous and potassium, which are two essential macronutrients. While your plants will grow in case of a boron deficiency, they won’t be as strong as they should be. They will die quickly and lose their flowering ability.

Want to learn how you can identify a boron deficiency? Let us help you.

How to Identify Boron Deficiency?

Upper young leaves will show the most obvious symptoms of a boron deficiency. You will notice the leaves yellowing and their tips becoming brown and then black before eventually dying off. On the other hand, the stems will show signs such as becoming brittle, and cracks will start appearing. Sometimes you will also notice hollow spots in the stem.

Different Crops and their Symptoms of Boron Deficiency

  • When they interact with calcium, Apple plants appear as a water core, and you will find internal parts of the fruit frozen.
  • The beetroot plant will become rough, and you will notice cankered patches on the plant's roots. You will also find a prominent brown rot that will appear internally.
  • Cabbage plants will have distorted leaves, and you will commonly find hollow areas in the stem.
  • Cauliflower plants will have roughened ribs, stems, and leafstalks. You will also notice poor curd development and brown patches.
  • Celery’s inner tissues will turn reddish-brown, and you will notice cracks on the upper surface.
  • Strawberries will show stunted growth, the foliage will become small, and the tips will become yellow and puckered. The fruits of the plant will also be small and pale.
  • Palm trees will have decreased productivity, and there will be brown spots on the fronds.

How to Fix Boron Deficiency?

The most important thing to keep in mind is maintaining adequate pH levels in both soil and hydroponic growing systems. A pH imbalance leads to blocking the plant’s nutrient uptake. If you want your plants to stay healthy and free of boron deficiency, it is important to ensure the pH level remains between 5.5 and 6.5. This pH range will allow the plant’s root system to take up the nutrients present in the soil quickly.

If pH levels are not in this range, regardless of the availability of micro and macronutrients, the plant will not be able to use them.

Other methods for fixing boron deficiency

You can also use nutrient supplements with kelp to fix boron deficiency. These supplements will give the plants a boron boost and give them a healthy dose of magnesium and calcium. Many growers also prefer using borax or boric acid.

They use boric acid-based foliar sprays, which are usable for soilless growing, soil, and hydroponic growing. Excess boron can prove to be highly toxic for your plants. If you want optimal results, keep concentration below 20 ppm.

Boron Toxicity Problem in Plants

The symptoms and signs of boron toxicity are the same as those of other nutrients. If you notice tip chlorosis, your plants are likely facing boron deficiency. However, this problem is more likely to occur with other nutritional deficiencies than boron.

With boron toxicity, the impact is relatively immediate. The toxicity quickly leads to the defoliation of plants and the death of the leaf. You will face toxicity issues either when you overapply compost to the soil or during the dry season.

If your plants suffer from a deficiency, you will find it extremely difficult to avoid toxicity. Why? Simply put, it is challenging to gauge between too little and too much. If you want to prevent toxicity, one way to do it is to keep the growing medium’s pH, the water’s pH, and the nutrient levels. If the growing medium’s pH is less than 5.5-6 or if boron has been excessively applied with the fertilizer, the likelihood of boron toxicity increases significantly.

It is highly unlikely that your plants will be affected by boron toxicity naturally. If you notice signs of toxicity, the best way to go about things is to conduct a soil test and find the real culprit and then flush out any extra boron. After this, use a calcium-based fertilizer so that the plants become unable to use boron at all. Do not forget to have the water tested before irrigation, and make sure the water doesn't have extra boron.


Always use a boron-free fertilizer if you are looking to fight other nutrient deficiencies. If you want to take preventative measures proactively, just get hold of a complete nutrient package and follow a feeding schedule, and you will probably never come across this issue. You can give our nutrient deficiency series a read to learn more about nutrients and deficiencies related to these nutrients.

Oct 2nd 2022
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