It may be that they were not all planted the same or perhaps some suffered more root problems prior to, during or after planting. Roses need soil firmed around their roots and watered in well at planting. Then they need moist but not soggy soil. The first summer is a critical one as the new plants are trying to get a root system established. If the entire bush died almost at the same time the problem is likely in the roots.
Roses in the hot sultry Texas heat can be a challenge but are very doable! The keys to great and productive roses here in Texas are:
1-Select varieties adapted to the heat.
2-Select a site with plenty of sunlight (6 hours minimum)
3-Build a slightly raised planting bed incorporating plenty of composted bark into the soil.
4-Keep the plants well watered but not soggy in the hot summer months.
5-Fertilize every 4 weeks from spring to early fall.
6-Protect foliage of susceptible varieties from powdery mildew, black spot, mites and aphids with appropriate sprays as needed.
7-Prune in February and again in late August to promote new growth for the fall blooming period.
I hope this helps. Try planting again in November as that is the best and easiest time to establish roses. Late winter is the next best time.
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