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Boron (B) Nutrient Deficiencies

Boron is an essential micronutrient necessary for plant growth but is required in very small quantities. Boron's role in the plant is not fully understood.

Boron (B) Nutrient Deficiencies

Boron is an essential micronutrient necessary for optimal plant growth and development, but is required in very small quantities. Boron's role in the plant is not fully understood.

Boron is taken up through a plant’s root system from its growing medium, in both soil and hydroponic growing systems, and through its leaves in foliar applications, and when a boron deficiency is detected, it becomes necessary to supplement with additional boron.

Why Is Boron Important?

Nearly all of a plant’s boron is found in its cell walls, and its most important role is aiding in cell wall formation, functioning and strength. Because of this, a boron deficiency will cause overall reduced plant development and result in nonproductive plants. Boron deficiencies are very rare and are often accompanied by a calcium deficiency. The occur most often when plants are under watered.

Potassium and phosphorus nutrition is enhanced by boron. Because of boron’s significant role in maintaining proper functioning and strength of plant cell walls, boron has a positive impact on root uptake of potassium and phosphorus, two vital macronutrients for our plants.

Identifying Boron Deficiency In Plants

Boron deficiency will still allow the plant to grow to a reasonable size, but in a weaker state, with death at growing points, and flowers and fruits will fail to develop. Leaf symptoms of boron deficiency will appear in the upper, young leaves. Slight yellowing may occur, and the tips of leaves will turn brown to black and die off.

The stems may also be affected by becoming brittle, displaying cracks along the surface of the stem, or becoming hollow.


  • Young leaves will experience tip burn
  • Young leaves will curl and wrinkle
  • Growing tips die
  • Root tips will swell and stop growing


Examples Of Boron Deficiency



Crop Specific Symptoms

  • Apples—interacting with calcium, may display as "water core", internal areas appearing frozen
  • Beetroot—rough, cankered patches on roots, internal brown rot.
  • Cabbage—distorted leaves, hollow areas in stems.
  • Cauliflower—poor development of curds, and brown patches. Stems, leafstalks and midribs roughened.
  • Celery—leaf stalks develop cracks on the upper surface, inner tissue is reddish brown.
  • Celeriac—causes brown heart rot
  • Pears—new shoots die back in spring, fruits develop hard brown flecks in the skin.
  • Strawberries—Stunted growth, foliage small, yellow and puckered at tips. Fruits are small and pale.
  • Rutabagas / Turnips—brown or gray concentric rings develop inside the roots.
  • Palm Trees—brown spots on fronds & lower productivity.


How To Correct Boron Deficiency

One of the first things to take a look at is pH balance, in both soil and hydroponic growing systems. A pH imbalance will block nutrient uptake through the plant’s roots. It is important to regularly check the pH, and to be sure to keep the pH within the appropriate range for soil or hydroponics. The optimal pH range for most plants is between 5.5 and 6.5. In this range, the nutrients present in the soil or water are soluble, and are easily taken up through the plant’s root system. When the pH level is outside of this range, even when appropriate levels of micro and macro nutrients are present, they are not able to reach the plant.



Another great approach to correcting a boron deficiency, is through supplementation. A nutrient supplement that contains kelp will give plants a much need boost of boron, along with the added benefit of calcium and magnesium.

Another method a lot of gardeners and growers like to apply is with the use of borax or boric acid. This simple supplementation method can be used in soils, soilless growing, hydroponic systems, and as a foliar spray.

Caution: The leaves of many types of plants are damaged by the application of boron so it is best to apply it to the soil or hydroponic solution. 

Household borax should be applied at a rate of ½ tsp. of borax with 1 gallon water. If you suspect a boron deficiency problem with your plants, a dose of borax will do the job.

Boron can quickly become toxic if applied in excess. Keep concentrations below 20 ppm under normal growing conditions for optimal results. Boron is sometimes a component of insecticide so it is best to avoid excessive amounts of boric acid-based products.

Now that you know the benefits of monitoring the boron content in your soil and hydroponic growing systems, and what to do when you spot a deficiency, you can be sure to have the necessary tools on hand to keep your plants at their best.



Want to learn more about nutrient deficiencies?

Read our entire nutrient deficiency series as well as learning about micro vs macronutrients.