Container gardens are a popular and convenient way to landscape around the house and deck, but potted plants need protection in order to survive a cold winter. Prepare your plants for winter by watering thoroughly until the first hard frost. Do not fertilize or prune container plants after mid-summer; doing so can encourage new growth that will be vulnerable to freeze damage. Choose plants that are hardy to at least two zones above your planting zone, and be aware that plants kept in the largest possible container will have the best chance of overwintering successfully.
Broadleaf evergreens such as boxwood and rhododendrons offer welcome green color during the winter and are hardy enough to overwinter as far north as zone 5. Ivy topiaries, especially those grown into interesting shapes, provide color and shape to the winter garden. Holly can be container-grown, and the bright red berries attract birds through the early months of winter.
Bark and Berries
Some plants have interesting bark that creates winter appeal. Red twig dogwood can be grown in a large container, and its reddish winter stems stand out against snow. Horizontal rockspray, pyracantha and bayberry produce long-lasting, deeply colored berries that are attractive to birds.
Lavender can survive the winter in a large container if it is heavily mulched and kept out of drying winter winds. The fragrant flower heads fade to a grayish green and persist all winter. Heather--a small, shrubby bush--maintains its shape and color well into winter as well.
Ornamental grasses die back in winter, but their dramatic foliage provides a strong vertical accent in the winter garden. Japanese silver grass, Japanese forest grass, blue oat grass and blue lyme grass are all hardy to zone 6 when grown in containers.
Hardy, spring-blooming bulbs like tulips and daffodils can survive in a container if they are well-protected. Place the pots in a protected area and mulch them well with straw. Summer bulbs like canna and caladiums will not survive sub-freezing temperatures.