Technical Abstract: Nickel was discovered to be deficient in pecan orchards, causing replant problems and symptoms known as "mouse ear". It was discovered that timely foliar sprays of nickel corrected or prevented mouse-ear and replant problems. Subsequent observations of other crops indicate that nickel is a limiting factor in many crop situations. Examples include River Birch, plum, peach, walnut, almond, apple, citrus, grapes, containerized woody ornamentals, and in certain tissue culture associated situations. Observations also indicate that Ni is a limiting factor in disease resistance of a variety of crops. Findings indicate that lack of understanding in nickel nutrition could be a major factor limiting profitability in a host of horticultural crops. Circumstantial evidence indicates that there are many modalities of unknown cause (or causes previously attributed to other biotic or abiotic factors) that are in reality tied to insufficient nickel.