Japanese aucuba is cold tollerant once established and doesnt need winterization after the first year.
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The Japanese aucuba is an evergreen shrub that is very tolerant of cold temperatures. Mature plants do not need protection from winter temperatures in zone 5 or warmer climates. Young Japanese aucuba may need some protection their first winter. Outdoor growing of Japanese aucuba is not recommended in climates colder than zone 5.
Cover the young Japanese aucuba plant completely with dry leaves or straw. Leave some air space and take care not to damage the leaves or branches.
Place a bushel basket or other basket over the leaves or straw. The basket helps hold the leaves in place and keeps some moisture off the mulch to maintain its insulating properties.
In the early spring, after the risk of deep freezing temperatures have passed, remove the basket and leaves. The Japanese aucuba will likely do fine if uncovered a few weeks before the last frost. If you are uncomfortable having it out unprotected for the last frost, leave the basket and leaves on until after your area's last frost.
Rake the leaves and, if desired, use them as mulch elsewhere in your garden or compost them for future use.