Good arum lily winter care comes down to one choice. In mild areas you mulch the crown and leave the plant in the ground. In cold areas you lift the rhizomes and store them somewhere frost-free until spring. The white Crowborough type shrugs off most winters, so your climate decides the job for you, not the calendar. Get that one call right and the rest is easy.
Last autumn I piled a thick blanket of bark and leaf mould over the white Crowborough crown in my own back corner. The spot stays damp and shady, so digging it up felt wrong. I tucked the mulch down around the buried rhizome and left it alone for the season. The following mild spring I checked that corner and found fat green spears pushing up through the cover. They came up right on time, none the worse for the cold. I had not lifted a thing all winter.
That scene shows the whole point of overwintering arum lily plants in the right place. The white species is tough by nature. It carries an RHS H4 hardiness rating. That means it handles roughly -10 to -5°C (14 to 23°F) without much trouble. Sitting in the ground with a real cold snap behind it, the rhizome stayed safe under that mulch. You can rely on the same trick if your winters stay mild.
Hardiness is what splits your two routes apart. The white arum lily takes USDA zones 8 to 10 in the ground. It stays put down to zone 8 with no fuss from you at all. Zone 7 is the edge of its range, where it pulls through only with real protection. Coloured hybrids are a different story for you. They bruise at the first hard frost and need lifting almost everywhere you grow them.
So pick your route by your own climate. Where the plant is hardy, mulch the crown deeply once the foliage fades. Use 5 to 8 cm (2 to 3 inches) of bark or leaf mould and then walk away. Where winters bite hard, wait for the foliage to die back first. Then lift and dry the rhizomes before the frost sets in. A few weeks of drying under cover keeps them firm enough to store well.
When you lift arum lily rhizomes, brush off the loose soil with your hands. Let them dry for a week or two in an airy shed or garage. Then pack them in a box of dry sand or shredded paper for the winter. Keep that box in a cold, dry, frost-free spot around 5 to 10°C (41 to 50°F) until spring. A garage shelf or a cool cupboard works fine for you, as long as it never freezes inside.
Check the stored rhizomes once a month through the cold season too. Toss any that turn soft, mushy, or grow grey mould, since one bad rhizome can spoil the rest of the box. The firm, healthy ones feel like a raw potato in your hand. Keep the box out of bright light and away from any radiator, because warmth wakes them up too soon.
A few small moves make a real difference to your plants. In borderline zone 7, try a deep mulch first and lift only if a brutal winter is forecast. Empty the saucers under any containers you keep outside. That way dormant rhizomes never sit in cold standing water, which rots them faster than frost ever does. Then uncover your crowns in spring once new growth restarts. Replant any stored rhizomes after the last frost passes, and your arum lily picks up right where it left off.
Read the full article: Arum Lily: Complete Care and Safety Guide
