Boron (B) is one of the micronutrients or trace elements, needed by plants in small or trace, but essential, amounts. It is important in plant cell formation and both vegetative and reproductive growth. A deficiency in the soil leads to poor and stunted growth and reduced fertility.
Other symptoms appear in plants, depending on the plant in question. These include:
- Apple: ‘water core’ in the fruit
- Beetroot: rough, cankered areas on the skin and internal brown rot
- Cabbage: distorted leaves and hollow stems
- Cauliflower; poorly developed curds with brown patches
- Celery: brown cracks in leaf stalks, coloured reddish brown inside
- Celeriac: brown heart rot
- Lettuce: stunted growth and leaf tip dieback
- Pear: new shoot dieback, fruit skin develops hard brown flecks and brown patches underneath
- Strawberry: small, yellow leaves and small, pale fruit
- Swede and turnip: brown concentric rings inside roots, leading to rotting
Although shortages of boron in the soil are not common, boron deficiency may be caused when there are insufficient suitable boron-containing materials in the growing medium (soil or compost). It is more likely to occur when boron is present, but is unavailable for plant roots to absorb – “locked” in the soil or compost. This is common in alkaline growing media, where the pH is above 7. It can also be caused when plants are growing in dry soil or compost, which prevents the roots taking up the boron.
Use a simple soil pH testing kit to make sure your soil is acidic – especially when growing lime-hating and ericaceous plants and those plants listed above.