Few apricot varieties are reliably hardy in Iowa. Moongold and Sungold are hardy and self-unfruitful. Plant at least one of each for proper pollination. Most varieties are self-unfruitful. Most peach varieties are self-fruitful.
Most European pears are self-unfruitful.
Plant at least 2 different varieties for maximum fruit production. However, European and hybrid plums can be successfully grown in the state. European plums are partially to entirely self-fertile. Plant 2 or more hybrid plum varieties to insure cross-pollination and fruit set. European plums will not pollinate the hybrid plums and vice versa.