Hydrangea 'Mahogany Pita' (likely 'Pia'): Hardiness, Size, and Winter Care

Pat has two 12-inch plants labeled 'mahogany pita' hydrangea, dark red, grown considerably in a month. Asks if annual/perennial and mature height.

Identification and Hardiness (C.L.)

Likely 'Pia', a dwarf hydrangea (12-18 inches). Most blue/red/pink hydrangeas are hardy only to Zone 6 (above 0°F). Below zero, they die to ground and won't flower next summer. 'Pia' flowers best if winter temps stay above 15°F. Since location unknown, use temperature guidelines to gauge survival.