While all outdoor perennial plants--those that live three or more growing seasons--live year round, many are deciduous, losing their foliage and going dormant over the winter. Reduced to their "skeletons," they don't look alive to many, so when people talk about plants that live during all the seasons, they usually mean evergreens. Evergreens include both needled plants and broad-leaved plants. These can provide flowers, fruit, color and screening through the bare winter season, regardless of your planting zone.
Rhododendron is a large genus, usually evergreen, with plants that can live in many climates. Azaleas are rhododendrons. The Lapland rhododendron can live in USDA hardiness zone 1, which has winter temperatures below 50 degrees Fahrenheit. (Zones change by 10-degree increments.) Besides producing flowers in spring and summer, the rhododendron has an interesting reaction to cold, drooping and curling its leaves as if turning inward.
Junipers, which come in different shapes, sizes and colors, can be used as a screens, including during winter. Junipers tend to be shrubby, for instance, the common juniper is only 5 to 10 feet high. Other junipers are trees, though, like the eastern red cedar that grows up to 50 feet high and 20 feet wide. Varieties of junipers can live in zone 3 all the way down to the warm lands of Florida.
Mountain laurels can live in the northern climes of zone 4 down to the milder weather of zone 9. They are broadleaf evergreens that grow 3 to 5 feet with dark green leaves that are maroon by the time the spring melts the snow off them. They like soil on the acidic side (below pH 7). Some varieties produce flowers in spring.
Hollies, which grow in zones 5 to 9, can be used as specimen plants, which are meant to draw attention to themselves, as foundation plants and as hedges and screens. The berries appear in fall and winter, feeding wildlife while providing color. Some hollies grow up to 40 feet; those for hedges, about 4 feet. Berries are not always red. Hollies can fruit in yellow, orange and even black.
Wax myrtle, which is also spelled as one word, is also called Southern bayberry or candleberry because the leaves have an aroma used to give scent to candles.The trees, which grow from zone 4 to 10, produce clusters of small fruit used as food by wildlife through the winter. Some birds can even eat the wax on the leaves.
Camellias only grow in southern zones, where they bloom during the winter. The flowers bloom up to 4 inches wide in white, pink, yellow and red. The leaves are glossy and thick, growing on shrubs or small trees. Camellias are very pest prone, but growers love their beautiful flowers.