Fertilising flowering ornamental trees
Quick answer
If a flowering tree grows vigorously but flowers poorly, the likeliest cause is too much nitrogen, not too little of anything. Before reaching for a product, check the four things that explain most cases: is the tree old enough to flower, is there enough light, was it pruned at a time that removed flowering wood, and was it recently transplanted?
Why more feeding usually backfires
FAO records that the effects of excess nitrogen include a prolonged vegetative period and delayed maturity. A tree with abundant nitrogen keeps building leaves and postpones flowering. Feeding a poorly flowering tree with a general-purpose product therefore tends to deepen the problem.
The nutrients genuinely linked to flowering
- Phosphorus — essential for growth, cell division, seed and fruit development and early ripening; its shortage delays ripening. But phosphorus added to a soil that does not need it produces no flowers.
- Boron — a key role in pollen tube growth, affecting seed and fruit set; deficiency reduces bud, flower and seed production. Never add boron on assumption — see the warning below.
- Zinc — flowering, fruiting and maturity can all be delayed under shortage.
Method — non-nutritional causes first
- Age. Many trees do not flower in their first years. Confirm the species' expected age.
- Light. Shade is a common and reversible cause.
- Pruning history. Pruning at the wrong time removes the wood that would have flowered.
- Transplant recency. A recently moved tree builds roots before it flowers, correctly.
- Then feeding. Vigorous leafy growth with poor flowering points to excess nitrogen — the answer is less, not more.
- Then analysis, if a genuine shortage is still suspected.
In Kuwait's conditions
Heat and wind at flowering matter as much as nutrition. Al-Suhily winds run 15 March to 10 April with maxima reaching 41°C, and spring thunderstorms average 65 km/hour — conditions that strip blossom and disrupt pollination regardless of how well fed the tree is. A poor flowering season following a windy spring is not evidence of a soil problem.
Common mistakes
- Buying a high-phosphorus product for poor flowering without an analysis.
- Continuing routine nitrogen feeding while wondering why flowering is poor.
- Adding boron because flowering or fruit set disappoints.
- Pruning at a season that removes the flowering wood, then blaming nutrition.
- Expecting flowering from a tree that has not reached flowering age.
Boron — a real risk, not a precaution
Boron has a narrow margin between sufficiency and toxicity. FAO records toxicity arising where irrigation water carries more than 1–2 ppm boron, and lists an occasional excess of boron among the problems of arid soils. In this region boron should never be applied on assumption — only after an irrigation-water analysis establishes the need, with specialist sign-off.
Related glossary terms
Sources
- FAO — Fertilizer and Plant Nutrition Bulletin 16, Chapters 3 and 4.
- Kuwait Meteorological Department — Climate.
All accessed 27 August 2026. Last reviewed: 27 August 2026.