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Wintertime at the National Arboretum

Shrubs, winter-blooming bulbs are hearty enough for the cold weather

By US National Arboretum | August 27, 2012

Winter can be long for garden lovers, but has its rewards.

Visiting the U.S. National Arboretum in Washington, DC during the off-season affords visitors scenes and garden treasures often missed during the spring and summer months.

Many shrubs have fantastic blossoms or berries that make the winter season sparkle.

Combining these shrubs with colorful, winter-blooming bulbs can sustain the avid gardener through the last droll months of winter. The following information is a guide to some of these treasured shrubs and bulbs.

Fragrance

Fragrance is one of the highlights of winter gardening. A very fragrant fall-blooming shrub at the Arboretum is sweet osmanthus (Osmanthus fragrans, USDA Hardiness Zone 7 – 10). . A short walk into the Asian Collections in November will have visitors looking around for that wonderful, fruity perfume and finding this holly-like tree. For an early whiff of spring, wintersweet (Chimonanthus praecox, Zone 7 – 9) can also be found there. Clear yellow cup-like blooms give off a distinctly sweet scent, reminiscent of jasmine in December and January. Extremely low temperatures can cause these shrubs to stop blooming early, though some buds will remain closed and begin to bloom again as soon as the temperatures rise.

March brings the blossoms of winter hazel (Corylopsis spicata, Zone 5 – 9). Long clusters of bell-shaped, incredibly fragrant yellow blooms cascade from zigzag branches to form a dense, yet see-through shrub. Visit the Friendship Garden around the Arbor House Gift Shop to see this shrub under-planted with Lenten rose (Helleborus sp., Zone 4 – 9), an evergreen, late winter-blooming perennial. Leatherleaf mahonia (Mahonia bealei, Zone 6 or 7 – 9) is also planted in the Friendship Garden and boasts gray-green, holly-like leaves and fragrant yellow blooms.

For more early flowering shrubs, visit our selection of witch hazels. Native witch hazels (Hamamelis virginiana, Zone 5 – 9) have clear, lemon-yellow blooms in fall. These can be found in Fern Valley (our native plant collection) and in the Azalea Collections. Asian species and selections of witch hazels can start blooming as early as December and continue through March, depending on the weather. February and early March are the peak bloom times for these showy, often fragrant witch hazels. Our favorites are 'Jelena' (bronzy-orange; see image at left), 'Luna' (clear yellow) and 'Arnold Promise' (bright yellow). Several new selections like 'Orange Peel', 'Barstedt Gold' and 'Angelly' were recently planted along the new Flowering Tree Walk in November.

Flowers

Throughout the Arboretum, there are other winter-blooming plants to enjoy. Though not fragrant, winter jasmine (Jasminum nudiflorum, Zone 6 – 9), is a more interesting, early alternative to forsythia, with its cascading yellow blooms and stiff deep green stems. This can be found at the south entrance of the Morrison Garden in the Azalea Collections in January. The fall-blooming camellia (Camellia sasanqua, Zone 7 – 9), gives life to early winter, while the Japanese camellia, (Camellia japonica) will reward you in late winter and early spring with a plethora of different bloom colors and shapes. Most of our camellias can be found in the Asian Collection.

Flowering trees are usually considered a harbinger of spring. However, while anticipating the cherry blossom season, visitors can see the flowering apricot (Prunus mume, Zone 7 – 9) begin to bloom in January and February (see image at right). Come March, the first magnolias and flowering cherries will begin to bloom in all their glory.

Berries and Fruit

For winter berries, explore the Holly and Magnolia Collections. Various selections of holly, (Ilex sp.; see image at left) display winter interest from fall until the magnolias bloom in spring. Hollies that are native to the United States include American holly (Ilex opaca) selections and the deciduous, winterberry holly (Ilex verticillata, Zone 5 – 9), which boasts clusters of red berries long after the foliage is gone.

Other winter berries are found in the Friendship Garden, where heavenly bamboo (Nandina domestica, Zone 6 – 9) combines dramatic clusters of red berries with exotic evergreen foliage. At the entrance to the Boxwood Collection, the red spray of winter king hawthorn trees (Crataegus viridis 'Winter King', Zone 4 – 7) make a vivid impression (see image at right).

Bulbs

Fall and winter-blooming bulbs can help fill the void from late summer until next spring’s daffodils. The pink trumpeted blooms of resurrection lily or naked lilies (Lycoris squamigera, Zone 5 – 9; see image to left) emerge in August, long after their foliage is gone. These are followed in September by the striking red blooms and stamens of spider lilies (Lycoris radiata, Zone 7 – 10). The large lavender blooms of autumn crocus (Colchicum sp., Zone 5 – 8) are also emerging in September. By late winter, dwarf bulbous iris are emerging in the Boxwood Collection and

Azalea Collections. Yellow Danford iris (Iris danfordiae, Zone 4 – 9) comes up with the crocuses and snowdrops by mid-February and purple or blue reticulate iris (Iris reticulata, Zone 4-9) follow in March. The yellow cups and whorled leaves of winter aconite (Eranthis sp., Zones 4 – 9) are also a welcome site in late winter.

The color of winter trees, shrubs and bulbs makes a winter visit to the arboretum worth the chill in the air. See the tables below for a summary of just a few shrubs and bulbs. The U.S. National Arboretum’s Hort Hot Spots and Average Blooming Dates Calendar are also great resources for locating the best plants for winter interest. After a winter visit to the Arboretum, visitors may be inspired to plant a few winter-blooming or fruiting plants to see them through the next year’s long winter season.