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Boron shortage: flowers without fruit, cracked stems, hollow hearts

Deficiency and toxicity are a thin sheet of paper apart.

Nutrient shortage
Speed
  1. A watering eases some drought drop; misshapen flowers and hollow hearts that stay are more boron.
  2. Toxicity also scorches margins and kills the growing point — it looks like shortage, so never double the rate.
  3. Never double boron; don’t pour boron onto dry soil; don’t broadcast without a test.
  4. Foliar boron (after boron is confirmed): Labelled lower rate, twice, from before bloom to first flower. A small patch first. Soil-applied commonly 0.5–1 kg per mu, follow a soil test. Never double the rate. Toxicity and shortage look alike
  5. Name what you see before you feed.
  6. If leaves, roots and the surface disagree, stop.
  7. Boron runs flowering.
  8. Deficiency and toxicity are a thin window.

What you see in the field

Bloom without fruit, dropped buds, hollow or split stems, growing point stalled.First the leaf position: new or old, even yellow or between the veins. If that does not match, do not fertilise yet. Pull one plant and read whether the roots are white, brown or foul.

A sketch. Do not fertilise from the picture alone.

Tap to enlarge. The caption says what to photograph. Missing field photos are marked as to-be-added.

Why it looks like this

The field looks like this because the root cannot take water or nutrients the usual way. Fix the soil condition first — drainage, salt, acidity, compaction or a salt of fertiliser — then a thin feed. Rates live in the range on this page; confirm with a local station and the label.

Easy to mix up

  • Looks like “Flower drop in a dry bloom”

    A watering eases some drought drop; misshapen flowers and hollow hearts that stay are more boron.

  • Looks like “Boron toxicity”

    Toxicity also scorches margins and kills the growing point — it looks like shortage, so never double the rate.

Do this / don’t do that

  1. 1Compare the worst plants with a neighbour ridge. Photograph whole plant, close-up and soil surface before you add fertiliser.
  2. 2Match roots, leaves and the soil surface to this guide. If they do not line up, do not copy a bag count.
  3. 3Use the rate range on this page only as a range. Confirm with a local station and the product label.

Don’t do this first

  • Never double boron; don’t pour boron onto dry soil; don’t broadcast without a test.

Rate range

Foliar boron (after boron is confirmed)

Labelled lower rate, twice, from before bloom to first flower. A small patch first. Soil-applied commonly 0.5–1 kg per mu, follow a soil test

Never double the rate. Toxicity and shortage look alike.

These are ranges. Confirm with your local extension station and the product label.

Available boron

The narrow door between shortage and toxicity

Low: hollow. High: scorched margins.

Flowers

The mark that boron did not move

Flowers that set nothing, hollow stems.

When you see Bloom without fruit, test. Take soil from the bad patch and from a greener neighbour, separately.

Lesson video

2026-03-20 · Li Zeyu · For learning. Serious damage: local agronomist or a soil test.

For learning only. Fertiliser and pesticide decisions need a local agronomist and a soil test.

Not sure? Photograph the field to identify the problem