Ask Mr. Smarty Plants

Although there could be reasons a female plant would not produce berries (e.g., no male trees near enough to provide pollen or some environmental cause such as a late freeze or heavy rains), there is a good chance that you have a male tree since you had no fruit. However, you need to see the flowers to tell for sure. The male flowers have functional stamens producing pollen. The female flowers have stamens that produce no pollen. Even though they are dioecious plants, they aren't always completely so. The female flowers generally have nonfunctioning stamens, but sometimes you will find perfect flowers—those with both a functioning pistil and also with stamens producing pollen.

You can see drawings of male and female flowers of possumhaw and yaupon on the USDA Plants Database. Note that the female flower has an enlarged ovary and stamens that are slender with no pollen. The male flowers have stamens that are fully developed with pollen. You can look at the blossoms in the spring (March, April, May) when both trees bloom to determine whether your tree is male or female.