Ask Mr. Smarty Plants

First, we need to check on some things to see if that gives us any idea on what is troubling your Rhus virens (Evergreen sumac). We always check first to see if the plant in question is native to the area where it is growing. This USDA Plant Profile map does, indeed, show that it grows natively in Bexar County. This plant must be popular in San Antonio, because we have a fairly recent previous question on Evergreen sumac, also from San Antonio.

When we followed the plant link to our webpage on that plant, under Distribution, we found this:

"Native Habitat: Rocky hillsides, gullies & bluffs. On rocky bluffs, slopes and banks, on dry hillsides in the Edwards Plateau and Trans-Pecos."

Here are the Growing Conditions listed on that page:

Water Use: Low
Light Requirement: Sun , Part Shade
Soil Moisture: Dry
Drought Tolerance: High
Cold Tolerant: yes
Soil Description: Rocky soils. Sandy, Sandy Loam, Medium Loam Clay Loam Clay, Caliche type, Limestone-based Igneous

So, it sounds like it is in the right place, and it was planted it in Winter, as all woody trees and shrubs should be. More research. Since you spoke of wilting leaves and new stems, we thought we should investigate Verticillium Wilt in Sumacs. We found two articles on the disease but one was from the University of British Columbia Botanical Gardens and one was in French; we didn't think either of those were going to pertain to Central Texas. We did, however, find a University of Illinois Extension article on Verticillium Wilt. It does include sumac as one of the plants susceptible to the disease.

Another article with some good information is from the University of Wisconsin Diagnostics of Vertilium Wilt. And (this is the last one, promise) University of Minnesota Verticillium Wilt of Trees and Shrubs. Read all these articles and check the actual symptoms in your sumacs against descriptions and pictures.

What occurs to us and probably to you, too, is that these references are all from northern states. Maybe we're overlooking something by not talking about a major problem with clay soils, which is drainage. From Dave's Garden, a forum, here is a comment on Evergreen Sumac, also from San Antonio:

"It can be killed by overwatering so the soil in which it is planted needs to be well drained."

If you amended your clay soil with compost or even some decomposed granite or sand when you planted the sumacs, drainage should not be a problem, but it is always something you should be aware of. Water will tend to stand in clay soil, shutting off oxygen and sometimes causing root rot.

Especially on the Verticillium Wilt, we suggest you contact the Texas AgriLife Cooperative Extension Office for Bexar County.  You should not consider planting the same plant in the same place if Verticillium Wilt is causing the problem, because that disease will reside in the soil, affecting only those plants susceptible to it.