Ask Mr. Smarty Plants

This Mr. Smart Plants did considerable database and Internet searching and consulted with several other Mr. Smarty Plants, but none of us has been able to find any specific information about whether Taxodium distichum (Bald cypress) is self-fertile or not.  Here is what I didn learn, however:

In angiosperms (flowering plants) there are several ways to insure that plants don't self-fertilize since self-fertilization decreases genetic diversity.  (You can read an outline of a lecture from Missouri State University about "Plant Sex" with information about angiosperm barriers to self-fertilization.)  For instance, the plants may be dioecious (male flowers occurring on a different plant from the female flowers).  This mechanism occurs in some gymnoperms [e.g., Juniperus ashei (Ashe juniper) and Juniperus virginiana (Eastern red cedar)].  Another way is that the male and female reproductive parts on the same plant may mature at different times.  I wasn't able to find any reference to this being the case in Taxodium sp. or any other gymnosperm.  The most common way that angiosperms avoid self-fertilization, however, is by being self-incompatible.   When a pollen grain from a plant lands on a stigma of the same plant, biochemical signals allow the plant to recognize the pollen as its own pollen and prevent it from fertilizing the ovule by inhibiting the growth of pollen tube.  This system, however, doesn't appear to function in gymnosperms.  A 1986 paper by Michael S. Zavada and Thomas N. Taylor ("The role of self-incompatibility and sexual selection in the Gymnosperm-Angiosperm Transition: a hypothesis."  THE AMERICAN NATURALIST, Vol. 128, no. 4, October 1986) states:  "The origin of intraspecific self-incompatibility (SI) is regarded as a significant event in the evolution of flowering plants. ... There are no documented cases of SI in gymnosperms."  

So, the upshot is that I don't see any reason why you can't plant just one baldcypress and still expect to get an optimal production of seeds for wildlife.  Gymnosperms are wind pollinated and this aids in self-fertilization as well as cross-fertilization.  If there are other Taxodium distichum trees in the general vicinity, your tree might even be pollinated by the pollen brought in by the wind from those.