Rosa gymnocarpa
Perennial.Flowers: 
April-July
April-JulySepals deciduous in fruit. Hypanthium not glandular, at most 2 mm wide. Prickles generally straight, not much thicker at base.
Photos
April-JulySepals deciduous in fruit. Hypanthium not glandular, at most 2 mm wide. Prickles generally straight, not much thicker at base.