Posts tagged ‘winter garden’

Preparing Your Trees for Winter

Japanese coral bark maple

Japanese coral bark maple (Acer ) in the Mary Livingston Ripley Garden, next to the Smithsonian Arts & Industries Building.

As we gaze around at the beautiful autumn colors that our trees are showing us, we’re trying not to think about the arrival of the cold and snowy weather of winter.  However, arrive it will, and now is the time to prepare your trees for those coming winter months.  Although all trees are potentially susceptible to winter injury, young and/or thin-barked, and broadleaf evergreen trees require the most preparation.

Excessively cold temperatures, wind, and quick temperature changes can cause drying, browning, and death of evergreen foliage.  This problem is most prevalent on broadleaf evergreens such as rhododendrons, laurels, boxwoods, and hollies.  To help prevent this damage, construct a barrier of heavy burlap, like a fence, to block drying winds from their prevailing direction.  If the entirety of the plant is exposed, loosely wrap it in burlap.  In either case, be sure to leave the top of the plant exposed so light and air penetration can still occur.  In addition, it is important to keep watering your trees up until the time of the first hard frost.  A 4-6 inch layer of mulch over the root zone will also help the soil retain warmth and moisture.  (Remember not to pile the mulch up against the trunk of the tree.)

Kean Hall Garden wrapped in burlap for winter.

The boxwoods in the Kean Hall Garden in Livingston, New Jersey wrapped up in burlap for the winter, 1955. Smithsonian Institution, Archives of American Gardens, Garden Club of American Collection.

Another issue of concern, which is also caused by rapidly fluctuating temperatures, is sunscald.  This occurs when the sun has warmed the trunk of the tree, and then that trunk is rapidly cooled upon sudden shading from a cloud, etc.  This condition results in elongated, dried and cracked areas of dead bark.  This can be prevented by wrapping the trunk with commercial tree wrap (available at most home and garden centers) or other light-colored material.  This will reflect sunlight and keep the bark at a more consistent temperature.  The wrap should be placed on the tree in the fall and removed in the spring, after the last frost.

Broadleaf evergreen foliage damage and frost cracks are influenced by many factors, including plant species, location, drainage, natural protection, and how well established a plant is in the landscape.  There is no specific temperature at which damage occurs, but if the forecast calls for temperatures below the average seasonal low (29-33°F for Washington, D.C.), it is best to utilize the protection methods outlined above.

Tree branches can be prone to breakage from heaving snow and ice loads and by strong winds.  Weakly attached, overextended and broken limbs should be pruned.  Trees with an upright form, such as juniper, arborvitae, and clump birch, can be wrapped in burlap, or held together by wrapping the branches collectively with twine or rope.  Any wrapping material should be removed in the spring.

When natural food sources grow scarce in the winter, rodents may feed on the young bark and cambial tissue of trees.  Plastic tree guards or a cylinder of ¼” wire mesh placed around the trunks of young trees will help prevent this damage.  Be sure to remove these guards once the spring has come so the tree does not wind up growing into them.

Trees possess an extraordinary ability to withstand severe winter weather, with some being more hearty than others.  However, with proper care and attention, your trees should come through the winter ready to show off their new flowers and foliage for spring.

-Greg Huse, Smithsonian Gardens Arborist & Tree Collection Manager

November 19, 2014 at 7:27 am Leave a comment

Winter Interest in the Garden

Just because it is winter does not mean that our gardeners or gardens get a rest.  Smithsonian Gardens welcomes visitors year-round.  These visitors include many tourists but also wildlife, as our gardens serve as an important urban habitat for birds, insects, and mammals.

Within our gardens you will find many plants that add winter interest beyond our impressive annual displays of pansies, violas, and kale.  Important garden features in this bleaker season include berries, grasses, seedheads, stems, bark, evergreens, and even some flowers.

Fruit and berries are a great way to brighten up a winter landscape and many serve as an important food source for birds.

Winter berries

Berries you will find in our gardens include (clockwise from upper left) Red Chokeberry (Aronia arbutifolia); American Holly (Ilex opaca); Firethorn (Pyracantha ‘Mohave’); Southern Bayberry (Morella cerifera); Beautyberry (Callicarpa dichotoma); Carmine Crabapple (Malus x atrosanguinea); and Winterberry (Ilex verticillata)

When selecting plants for winter berries note whether they are deciduous or evergreen.  The pointed rich green leaves of the American Holly above create a great contrast to the bright red berries while the Winterberry (Ilex ‘Sparkleberry’) below looks better with a solid backdrop like an evergreen to best stand out.

Winter berries

Winterberry (Ilex ‘Sparkleberry’)

Grasses and sedges add texture to our gardens in winter and some add great color as well.  Many of the grasses also provide seeds for birds in winter and nesting materials come spring.

Winter grasses

Some of the grasses and sedges you will find on our gardens include (clockwise from upper left) Leather leaf sedge (Carex buchananii ‘Red Rooster’); Switch Grass (Panicum virgatum ‘Cloud Nine’) [close-up and full plant]; Orange New Zealand Sedge (Carex testacea); and Pink Muhlygrass (Muhlenbergia capillaris) [pictured in November and January]

Seedheads create interest with varying shapes and textures and make a dynamic feature in winter as they mature and disperse.

Seeheads

Seedheads and pods that draw attention in our gardens include (clockwise from upper left) False Indigo (Baptisia australis); Purple Coneflower (Echinacea purpurea); Okra (Abelmoschus esculentus); Common Milkweed (Asclepias syriaca); Goldenrod (Solidago spp.); Whitehair Leather Flower (Clematis albicoma); and Upland Ironweed (Vernonia glauca)

Remember these seedheads are the result of earlier flowers from plants that have multiple seasons of interest.  Some of these seeds are now food sources for birds,  but their flowers were nectar sources, or some had foliage that fed caterpillars, in earlier seasons.  Take the Wild Senna (Senna marilandica) below, for example. It is a wonder native plant with nectar-providing pea-like flowers and is a host plant for sulfur butterflies in the summer.

Wild Senna (Senna marilandica)

Wild Senna (Senna marilandica)

Differing barks and branches also play a significant role in enhancing our gardens in winter.  Peeling barks of birches, brightly-stemmed twig dogwoods, and the towering dry stems of perennials can all become dominant features in the winter.

Bark and Branches

Some of our most striking stems in the gardens are seen with (clockwise from upper left) Paper Birch (Betula papyrifera ‘Renci’); River Birch (Betula nigra ‘Heritage’); Hollow Joe Pye Weed (Eutrochium fistulosum); Tatarian Dogwood (Cornus alba ‘Bud’s Yellow’); Coral Bark Japanese Maple (Acer palmatum ‘Sangokaku’); Crape Myrtle (Lagerstroemia ssp.); Red Twig Dogwood (Cornus sericea ‘Baileyi’); and Paperbark Maple (Acer griseum)

Evergreens are a key element to add structure in gardens during the winter.  There are a variety of evergreens available with a myriad of shapes, textures, and even colors.  Evergreens can be needled conifers but also broadleaf trees and shrubs and even some perennials hold their foliage in the winter months.  They also provide important cover and shelter for many species in winter.

Evergreen Perennials

A small sampling of our many needled evergreens include (clockwise from upper left) Eastern Redcedar (Juniperus virginiana ‘Burkii’); Umbrella Pine (Sciadopitys verticillata); Irish Yew (Taxus baccata ‘Fastigiata’); Japanese Cedar (Cryptomeria japonica); and Scotch Pine (Pinus Sylvestris ‘Burghfield’)

Broadleaf Evergreens

Some of the more dominate broadleaf evergreens in our gardens are (clockwise from upper left) Southern Magnolia (Magnolia grandiflora); Lantanaphyllum Viburnum (Viburnum x rhytidophylloides); Sweetbay magnolia (Magnolia virginiana); English Cherry Laurel (Prunus laurocerasus ‘Otto Luyken’); Common Boxwood (Buxus sempervirens); and Oregon Grape (Berberis aquifolium)

Lastly we can’t forget about winter flowers.  There is not much that blooms at this time but those flowers that do truly give us reason to celebrate.  They are also important nectar source for late and earl- season pollinators.

Winter Flowers

Blooms you can spot in Smithsonian Gardens in winter are (clockwise from upper left) Lenten Rose (Helleborus x hybridus); Common Witchhazel (Hamamelis virginiana); Sasanqua Camellia (Camellia sasanqua ‘Jean May’); Paperbush (Edgeworthia chrysantha); Stinking Hellebore (Helleborus foetidus); and Beale’s Mahonia (Berberis bealei)

I encourage you to take a walk through our gardens on a nice winter day and see what interesting plants you spot.

-James Gagliardi, Smithsonian Gardens horticulturist

January 7, 2014 at 7:30 am 2 comments


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