A truly hardy red coreopsis has been the Holy Grail of breeding for some time. The red color of ‘Mercury Rising’ comes from Coreopsis rosea, a perennial hardy through Nova Scotia. ‘Mercury Rising’ has been grown in central Massachusetts in zone 5 for three years and has thrived in sub-zero temperatures.  Slightly taller than CC. rosea, ‘Mercury Rising’grows 18-inches tall and spreads 30- to 36-inches wide. It's being offered by Sunny Border Nurseries.