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Boron Deficiency

Boron Deficiency

Disorderalso: Brown heart, Internal black spot, Corky core, Cracked stem

A nutritional disorder, not a disease, in which a plant runs short of boron and shows it as dead growing points and dark, corky, cracked tissue inside its fleshy roots and stems. Boron is needed only in tiny amounts, but the margin is narrow, and beets, turnips, and cole crops like cauliflower, broccoli, and celery are the classic crops to show a shortage first.

🔎 How to spot it

On beets, look for necrotic crosshatching inside the leaf stalks, young center leaves that brown and die into a rosette of small dead leaves at the crown, and dark internal and external black spots of dead tissue in the root. The growing point often dies and the plant throws multiple crowns, and the stalks crack and turn corky. In cole crops it shows as brown, water-soaked tissue (brown heart) and hollow, cracked stems.

🥀 Damage it causes

A boron-short plant stops growing at the tip and lays down dead, corky brown or black tissue inside the root, which both ruins eating quality and cracks the root open so soft-rot organisms can enter and turn the canker mushy. Severe deficiency kills the growing point outright and deforms the crop. The dead corky tissue is permanent and cannot be undone once it forms.

🔬 What causes it

Boron is required in very small amounts and is easily short. It leaches quickly out of sandy, light soils, becomes locked up and unavailable when the soil pH is high from over-liming, and moves poorly to the roots in dry soil, so a drought can trigger symptoms even when boron is present. The amount of available boron, not just the total in the soil, is what matters.

🛡️ Prevent it

Test the soil before adding any boron, because the gap between too little and toxic is the narrowest of any nutrient. Keep the pH in range and do not over-lime, build soil with organic matter, and water evenly so boron keeps moving to the roots. Add a measured boron source only when a soil test calls for it, and never broadcast extra as insurance.

🧯 If it is already here

Correct a confirmed deficiency with a carefully measured boron source: a dilute foliar spray of about one pound of actual boron per acre, scaled down for a garden and applied twice in midseason, greens the plant up and corrects symptoms, or work a measured amount of borax into the soil per the soil test. Tissue that is already corky and dead will not heal, so the goal is to protect new growth and the next crop.

💡 Good to know

Boron has the narrowest safe range of any nutrient: the dose that fixes a deficiency is close to the dose that poisons the soil for sensitive crops like beans, so always measure and never guess. Beets, turnips, cauliflower, broccoli, and celery are the indicator crops -- if they show brown heart or corky cracked roots, the rest of the garden is probably low in boron too.

🌱 Plants it affects

83 plants in the library can be affected by this problem

Arugula🥕Atomic Red Carrot🥕Black Spanish RadishBok Choy🥕Bolero CarrotBraeburn AppleBroccoli RabeBrussels SproutsBull's Blood BeetBurdockCalabrese BroccoliCeleriac🥬Champion CollardsChantenay CarrotCheddar CauliflowerCherry Belle RadishChinese BroccoliChioggia BeetClimbing Prairie RoseCortland AppleCosmic Crisp AppleCosmic Purple CarrotCylindra BeetDaikon RadishDanvers CarrotDe Cicco BroccoliDetroit Dark Red BeetDragon CarrotDwarf Blue Curled Vates Kale🥬Dwarf Siberian Kale🌸Easter Egg Radish🥕French Breakfast RadishFuji AppleGala AppleGolden BeetGraham Thomas English RoseGranny Smith AppleGreen CabbageHakurei TurnipHansa Rugosa RoseHoneycrisp AppleHorseradishIceberg Floribunda RoseImperator CarrotJanuary King CabbageKnock Out RoseKohlrabiLacinato KaleMcIntosh AppleMister Lincoln Hybrid Tea RoseMizuna🥕Mokum CarrotNantes CarrotNapa CabbageNew Dawn Climbing Rose🥕Paris Market CarrotParsnipPeace Hybrid Tea RosePink Lady Apple🥦Purple Cape CauliflowerPurple Sprouting BroccoliPurple Top TurnipQueen Elizabeth Grandiflora RoseRed CabbageRed Delicious AppleRed Russian KaleRedbor KaleRomanesco CauliflowerRutabagaSalsifySavoy CabbageSea Kale🥦Snowball CauliflowerSugar AppleSunchokeSweet Chariot Miniature RoseSweetheart CabbageTall Utah CeleryTatsoiWatercress🥕Watermelon RadishWhite Mustard🥕White Satin Carrot

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.