Ask Mr. Smarty Plants

Neither the names Juniperus coahuilensis, redberry juniper,  nor Juniperus texensis appear in our Native Plant Database. However, further search online in the USDA Plant Database did provide the fact that it is, indeed, native to North America. Our Native Plant Database is an ongoing work in progress, and this will probably get added someday. However, in further search, we found several scholarly articles on Juniperus coahuilensis, including this one from treesofnorthamerica.net. The major problem in getting precise facts about this tree is that it grows in areas where it apparently interbreeds with other closely related junipers.

Digging a little further, we searched on Juniperus texensis, and learned that is a synonym for Juniperus pinchotii (Pinchot's juniper), which is in our Native Plant Database. By following that link to our page on Pinchot's Juniper, which read, we learned that is also referred to as "redberry juniper" as is the J. coahuilensis. 

From the Gymnosperm Database, we found the only reference to age, on Juniperus pinchotii (Pinchot's juniper).

"Oldest

Ages to 175 years have been reported from isolated buttes in Garza County, Texas (Ellis and Schuster 1968, Mullins and Mitchell 1996)."

Unhappily, the answer to your question about average age is-we don't know and can't find out. We can say, from our research, that other members of the Juniperus family do live longer, up to 300 years, but very little research on tree age, especially in the remote areas in which these trees grow, means there just isn't any data to even use in making averages. Looking at the one figure we have, 175 years being the oldest, we would guess whichever of these junipers is the tree you are asking about would have an average age of about 100 years. This is purely a Mr. Smarty Plants guess, no quoting us in scholarly papers or using it to answer an exam question.