If a fruit variety requires a pollenizer, you must plant a second, different variety, usually of the same fruit type - and the two varieties' bloom periods must overlap.

Note that some varieties described as self-fruitful can set bigger crops if planted with a pollenizer, e.g. self-fruitful apricots often benefit from cross-pollination. Also, self-fruitfulness can vary with climate. Bartlett pear, for example, is self-fruitful in the western U.S., but not in eastern states.

Many apple varieties are sufficiently self-fruitful for home planting, especially in western U.S. climates, but require cross-pollination for consistent, maximum crops in commercial plantings.

Obviously, there is a great advantage in self-fruitful varieties for plantings where only one tree of each fruit type is wanted.