How to overwinter petunia 'supertunia royal velvet'

Petunia 'Supertunia Royal Velvet' is hardy to roughly USDA zone 10 — winter lows around -1°C. That means it will not survive frost and needs to come inside. Petunia 'Supertunia Royal Velvet' is frost-tender, so overwintering means bringing it inside and letting it rest rather than pushing it to grow. Move it indoors well before the first frost, give it the brightest spot you have (light levels indoors drop sharply in winter), and keep it away from both cold window glass and hot radiators — the swing between the two does more damage than the cold itself.

Bring indoors when nights start dropping below about 10°C, ahead of the first frost.

Cut watering right back — petunia 'supertunia royal velvet' uses far less while growth slows, and cold, wet compost is the usual cause of winter root rot. Stop feeding until spring.

Watering on the same schedule as summer. In winter that keeps the roots sodden while the plant is barely drinking, and petunia 'supertunia royal velvet' rots from the base.