development. Usually 5 to 6 years are required for grafted trees to come in to production, although some cultivars such as ‘PA-Golden (#1)’ may produce crops 4 to 5 years after planting (Pomper et al. 2003).

Seedling trees examined in this study had been planted for 8 years prior to the start of data collection. Vegetative vigor varied among populations in this study and a number of trees still did not produce fruit in 2002. Trees which were larger in terms of TCSA, and therefore have a higher biomass, were found to produce a greater number of clusters and have a higher total yield by weight. TCSA did not affect the percentage of flowers that formed clusters. Trees with a greater TCSA did produce more flowers than smaller trees. TCSA also increased at a greater rate between 2003 and 2004 (65% increase) than between 2002 and 2003 (39% increase), likely because very few fruit were produced on trees in 2003, leaving most of the trees resources to go into vegetative growth rather than fruit production. Although precocity data for these populations was not examined, earlier unpublished data collected by Pomper noted that trees in the New York population, that was also the largest in TCSA also flowered and produced fruit in 2001, earlier than trees in the other populations.

The tropical Annonaceae relatives of the pawpaw, cherimoya (Annona cherimola), sweetsop or sugar apple (A. squamosa), soursop (A. muricata), and atemoya (A. squamosa × A. cherimola), also have low yields due to low rates of natural pollination (George et al., 1992; Pena et al., 1999; Peterson, 1991). In commercial plantings, these tropical pawpaw relatives are hand pollinated to increase yields (Pena et al., 1999; Peterson, 1991). Pawpaw trees often produce large numbers of flowers but may set few fruit. This is true of many tree fruits, with typical fruit set of apple ranging from 2-8%, and an average of 15-20% fruit set in peach (Chaplin and Westwood, 1980). Pawpaws in the wild have also been reported to have very low fruit set, with less than 1.5% fruit set reported by Willson and Schmeske (1980) in native Illinois pawpaw patches, and 3.4% fruit set recorded by Lagrange and Tramer (1985). This study found that trees that produced a higher number of flowers also produced more fruit. Percentage fruit set in pawpaw ranged from 5-15% in this study, which is comparable to other tree fruits. However, fruit set was not found to be significantly different between populations except in 2003, when the Maryland population had the highest fruit set. Flies and beetles are