Fruit Trees (General)

Fruit tree fertilization requires a fundamentally different mindset than annual crop or garden fertilization because trees are long-lived organisms that draw on stored nutrient reserves, respond slowly to inputs, and can be seriously damaged by well-intentioned over-feeding. The single most important diagnostic tool is measuring annual terminal shoot growth — not soil tests, not leaf color, not fruit production. The UConn Soil Testing Lab and virtually every state extension service agrees: apple trees should produce 8-12 inches of new growth per year, pears about 8-15 inches, stone fruit (peach, cherry, plum) 12-18 inches, and mature trees that have reached desired size should be fertilized at 50-75% reduced rates to avoid excessive vegetative growth. If growth exceeds these targets, reduce or skip fertilization entirely. Nitrogen is the nutrient that fruit trees respond to most dramatically, and it is also the nutrient most likely to cause problems when over-applied — excessive vegetative growth (water sprouts), reduced fruit color and sugar content, delayed fruit maturity, increased susceptibility to fire blight (pears) and winter injury, and decreased flower bud formation for next year's crop. The timing of nitrogen application matters enormously: apply in late winter to early spring before bud break so nutrients are available during the critical bloom-to-fruit-set period when trees transition from using stored reserves to active soil uptake. Never apply nitrogen after mid-June in northern climates as late-season growth will not harden off before winter. Boron deficiency is common in New England fruit orchards and requires periodic supplementation with Borax at precise rates (excessive boron is toxic). Zinc deficiency, common in alkaline soils, requires dormant foliar spray rather than soil application for effective correction.