Cherimoya (Annona cherimola) makes an outstanding small landscape tree for gardeners in frost-free areas. While the flowers may not be considered beautiful, they have a pleasant fragrance, and the foliage is attractive and green for most of the year. Cherimoya flowers are pollinated by hand because there are no natural insect pollinators in North America. The tree grows best in U.S. Department of Agriculture plant hardiness zone 10. It will also grow in zone 11, but it won't flower or produce fruit unless it receives 50 to 100 hours of temperatures below 45 degrees F in winter.