How to overwinter dahlia 'bishop of llandaff'

Dahlia 'Bishop of Llandaff' is hardy to roughly USDA zone 8 — winter lows around -12°C. That means it survives outside in mild areas, but wants shelter in a hard winter. Dahlia 'Bishop of Llandaff' can stay outside over winter in most areas, but appreciates some protection in a cold snap. Mulch generously over the root zone, move containers against a sheltered wall (pots freeze far harder than open ground), and have horticultural fleece ready for the worst nights. The roots are what you are protecting — top growth can be sacrificed and regrown.

Mulch and move pots into shelter in late autumn, before the first hard frosts.

Water rarely, and only in dry spells — winter wet is a bigger risk than winter cold. Make sure containers drain freely.

Leaving dahlia 'bishop of llandaff' in a pot standing in a saucer of water. Waterlogged compost freezes solid around the roots and kills plants that would have survived the cold perfectly well.