Boron deficiency
Brown, grey or glassy tissue inside the root of a swede, turnip or beetroot, or brown cracks across the ribs of celery, on a plant whose leaves may look almost normal. It is the deficiency that hides: nothing on the outside says which of a dozen things is wrong, and the diagnosis is made by cutting one root open. Common on light, limed or drought-stressed soils, where boron either washes out or becomes unavailable.
What brings it on
Light sandy soils, soils recently limed above about pH 7, and dry summers — boron is both easily leached and less available as pH rises, so over-liming a brassica bed to deter clubroot can induce it. Growth is checked before the internal browning appears, which is why the sign is found at harvest.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Boron deficiency
- Agriculture and Horticulture Development Board — AHDB: Boron in field vegetables
Checked 2026-08-13
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Keep organic matter up and moisture even, and do not lime beyond what the crop needs. On ground with a history of brown heart, a boron application before sowing is effective — and is the one nutrient where the margin between enough and toxic is narrow enough that the rate on the packet matters more than usual.
Sourced guidanceDepends on conditionsmoderate confidence
Applies when: Only where a soil test or a repeated history of internal browning supports it. Boron is toxic to plants at modest excess.
- Agriculture and Horticulture Development Board — AHDB: Boron — application rates
Checked 2026-08-13
Dealing with it once it is there
- Nothing recovers a root that is already brown inside. The finding changes next season's soil management rather than this season's crop, and roots with limited browning are still edible once the affected tissue is cut away.
source
GrowingHQ editorial positionhigh confidence
Stated so the differential does not imply a mid-season rescue for a sign that only appears at harvest.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13
What it affects
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.