Extension Master GardenerSM Volunteers of Buncombe County

Landscaping

Plant Hardiness Zones: Why Are They Important?

“How low can you go?” is not only a term used in limbo dancing! Understanding the winter low temperature extremes in your gardening location is one of the most important pieces of information you need when selecting plants or seeds from nurseries or plant catalogs and is crucial to the survival of your plants.

 What are plant hardiness zones?

The United States Department of Agriculture’s (USDA) Agricultural Research Service (ARS), in cooperation with the PRISM Climate Group at Oregon State University, has developed an interactive mapping system that divides the United States into plant hardiness zones.

  • The most recent (2012) version of the map has 13 zones and includes all 50 states and Puerto Rico.
  • The numbered zone designations in this map represent the average annual extreme minimum temperatures at given locations.
  • The lower the zone number, the colder the zone.
  • Each zone is a 10º F band that the USDA further divides into 5º F zones “a” and “b” based on an average of the single coldest temperature recorded each winter during the 30 years from 1976-2005.

 Note: the zones do not reflect the coldest it has ever been or ever will be at a specific location, but the average lowest winter temperature for the location over the specified time period.

USDA Hardiness Map-Stuart Rankin-BY-NC-ND-2.0
Plant Hardiness Zone Map

 Why you should pay attention to plant hardiness zones.

Most plant labels and seed packets for perennial plants will include the zone hardiness information. Make sure you check the zone before you make a purchase to ensure that you are not choosing plants that will not survive the cold! This is particularly important when choosing expensive trees and shrubs! You may get lucky and have a prized plant live for a few years if we have mild winters, or longer if you have a favorable microclimate in your yard, but you’ll do better to make landscape choices from plants that thrive in your zone.

Hardiness Zone picture-B-Wardwell
Plant Label showing Hardiness Zones

 What is YOUR plant hardiness zone?

North Carolina plant hardiness zones range from 5b to 8b.

  • Zone 5: Minimum temperatures: Zone 5b -15 to -10º Examples of North Carolina locations in 5b: Mount Mitchell, Grandfather Mountain, Beech Mountain.
  • Zone 6: Minimum temperatures: Zone 6a -10 to -5º F, Zone 6b -5 to 0º Examples of North Carolina cities in 6a: Boone, Linville, Hot Springs; 6b: Cherokee, Maggie Valley, Little Switzerland.
  • Zone 7: Minimum temperatures: Zone 7a 0 to 5 F, Zone 7b 5 to 10º Examples of North Carolina cities: 7a: Asheville, Swannanoa, Lake Lure; 7b: Marion, Morganton, Charlotte.
  • Zone 8: Minimum temperatures: Zone 8a 10 15 F, Zone 8b 15-20º Examples of North Carolina cities in 8a: Fayetteville, Greenville, Wilmington; 8b: Nags Head, Duck, Corolla.

 BUT Buncombe County includes areas from 5b to 7a!

To find your specific hardiness zone use the USDA interactive map:   https://planthardiness.ars.usda.gov/PHZMWeb/InteractiveMap.aspx

Enter your zip code, and then zoom in to find your own address. The color-coded zone map will tell you if you are 5b, 6a, 6b, or 7a and the lowest average winter temperatures you can expect.

Article by Bob Wardwell, Extension Master GardenerSM Volunteer.

 Read more:

https://planthardiness.ars.usda.gov/PHZMWeb/About.aspx

 

Groundcovers Part V: Made for the Shade

Rudyard Kipling was right when he said, “Gardens are not made by singing ‘Oh, How Beautiful’ and sitting in the shade.” But there are times when gardens are in the shade: spaces at the forest’s edge, under trees, or in dappled light. These locations are ideal for the many shade-loving groundcovers.

Stepping stones through moss garden_tanakawho_CC BY NC 2.0_Flickr
Moss garden
  • Moss: Moss in the garden is either a problem or an opportunity! Non-flowering and lacking a root structure, moss gets its nutrients from air and water rather than soil and spreads by spores, not seeds. If it is thriving, it means that the soil is acidic, lacking fertility, shaded, moist, and/or compacted. You can spend time and money trying to change the soil conditions to grow other plants, which may or may not work. A more economical and equally satisfying option is to take a page from the ancient Japanese gardening tradition of landscaping with moss.
    Pros. Beautiful in rock gardens and along pathways, moss provides year-round color, with varieties ranging from blue-green to emerald green to yellow-green. Its velvety texture is particularly striking around tree roots and between stepping stones. Moss absorbs water quickly, helping to reduce stormwater run-off and erosion.
    Cons. Moss can be a slow grower, challenging a gardener’s patience, and picky about its environment—different species demand different conditions. A common misconception is that moss only grows in the shade, so check with your trusted garden center or native plant purveyor to find species that do best in your garden conditions.
  • Foam flower (Tiarella): This cousin of coral bells (Heuchera), another shade garden favorite, features “foamy” pink or white spring blossoms. Tiarella prefers well drained, “humusy” soil. Dappled sunlight brings out the best in its stunning foliage, but it also performs well in full shade. The Missouri Botanical Garden recommends planting Tiarella in shaded rock gardens, woodland gardens, border fronts, wild gardens, naturalistic plantings, or moist areas along stream banks.
  • Dwarf crested iris (Iris cristata): This petite (3 to 6 inches) North Carolina native iris spreads quickly, producing a spectacular drift of color in early spring. It is an excellent addition to rock gardens, perennial borders, or woodland gardens. White, pale blue, lilac, or lavender flowers with gold falls appear on very short stems. Following bloom, the foliage provides a strong, green groundcover for the remainder of the year. Hummingbirds and bumblebees like it—deer don’t!
  • Barrenwort, fairy wings, Bishop’s hat (Epimedium): There are many lovely varieties of Epimedium, all of them well-suited to shade. These small perennials (6 to 8 inches) feature red-tinged, heart-shaped leaves and, in the spring, delicate blossoms on wiry stems. Epimedium thrives in organically rich, moist, well-drained soil.
  • Wild ginger (Hexastylis ): North Carolina is the epicenter of Hexastylis, boasting 10 species, sometimes called “little brown jug.” Hexastylis arifolia, with its beautiful evergreen heart-shaped leaves and small brown jug-shaped flower, is a wonderful shade groundcover in woodland gardens. It prefers rich, moist soil where it grows slowly in isolated clusters of six to eight inches.

Putting it all together
Shade-loving groundcovers are fitting partners for other shade plants, such as ferns, hostas, Japanese anemone, trillium, and hellebores, and shrubs—including evergreen Japanese plum yew, for example, which works beautifully in partial shade. Together they create a serene beauty that few gardeners (or admirers) can resist. 

Groundcovers aplenty for shade, sun, and in between
When it comes to groundcovers, we have a multitude of choices well-adapted to sun, part sun, or shade. Check back through this five-part series on groundcovers to get more ideas.

There are aesthetic as well as practical reasons to invest in groundcovers. These often-humble plants bring texture and beauty to our gardens. Perhaps Alison Arnold, Buncombe County’s Extension Agent for Agriculture and Consumer Horticulture, said it best when she described them as “the fine linens of landscaping.”

Article written by Janet Moore, Extension Master GardenerSM Volunteer.

Read more
Common Mosses of the Northeast and Appalachians
Book by McKnight, Rohrer, Ward, and Perdrizet (Princeton University Press, 2013)

The Magical World of Moss Gardening
Book by Annie Martin (Timber Press, August 2015)

Managing Moss in the Landscape
by Paige Burns, NCSU Extension Agent, Richmond County, NC

Foam flower (Tiarella cordifolia)
by Missouri Botanical Garden

Plant Files by NC State Extension
Iris cristata (Dwarf crested iris) 
Epimedium x versicolor ‘Sulphureum’ (Bicolor barrenwort)
Epimedium sempervirens (Bishop’s hat)
Epimedium x youngianum ‘Niveum’ (White epimedium)

Hexastylis arifolia (Wild ginger or little brown jug)
by North Carolina Native Plant Society, Native Plant Gallery

Groundcovers Part IV: Shining a Spotlight on the Sun Lovers

“Plants that creep, crawl and spread over the earth like a warm quilt are called groundcovers. They are the fine linens of the landscape. Insulating in winter and sealing in the earth’s cool moisture in summer, these living blankets have an important place in the garden.”
Alison Arnold, Extension Agent, Agriculture-Consumer Horticulture
Mountain Xpress, April 28, 2004

Violet_Viola labradorica in flower_Sara_CC BY-NC 2.0_Flickr
Violet

Landscaping hot, dry places can be a challenge. When it comes to groundcovers, however, gardeners have a rich variety of options that not only protect against erosion, but also provide color and texture. Once you’ve tested the soil pH and done a sun study, it’s time to make your choices. These are plants that thrive in well-drained soil—sun-loving groundcovers don’t like, “wet feet.” They are especially well-suited to banks and slopes, borders, pathways, and rock gardens. Here are some winners that are low maintenance—and many are deer-resistant.

  • Violet (Viola labradorica): This long-blooming North American native does surprisingly well in the south, especially in mountain gardens. Its purplish-green leaves and delicate lavender flowers are a welcome sight in spring and summer for butterflies and bees. This low-grower (4 to 8 inches) prefers moist, well-drained soil and succeeds in full sun to partial shade. With no serious insect or disease problems, this is a groundcover you plant and forget. Just make sure that you are buying the native Viola labradorica and not the non-native Viola riviniana!
  • Dwarf mondo grass (Ophiopogon japonicus): Easily mistaken for Liriope, this dwarf grass-like plant is a finer-textured groundcover choice that makes a stunning feature along borders and pathways and between stepping stones. Just 2 to 4 inches tall, dwarf varieties have tiny flowers that are white or light lilac. It is both drought-tolerant and deer-resistant.
  • Creeping thyme (Thymus serpyllum): Where does the thyme go? If it is creeping thyme, plant it in dry, warm, sunny spots. This makes a perfect groundcover for rock gardens, the edges of garden beds, between stepping stones, and cascading down rock walls where soil is dry, light-textured, and bathed in sunlight. This aromatic groundcover creates dense, sprawling green mats that can withstand “tromping,” making it an excellent choice for high traffic areas. It is evergreen, deer-resistant, and produces lilac to purple flowers in the summer months.
  • Creeping St. John’s wort or Aaron’s beard (Hypericum calycinum): Creeping St. John’s wort is also an excellent groundcover, especially on slopes. Drought tolerant once established, this 12- to 18-inch plant spreads easily to 2 feet, so when planting be sure to allow plenty of room. St. John’s wort prefers fertile, loamy, well-drained acidic soil. Because it blooms on new growth, St. John’s wort benefits from old wood pruning in the fall but otherwise is maintenance free. The cultivar ‘Brigadoon’ sports chartreuse-yellow foliage and provides a pop of color that only intensifies in the summer when it is covered in yellow blossoms. Cooperative Extension Agent Minda Daughtry says “Brigadoon is one of my ‘set it and forget it’ low maintenance plants that makes me smile for the most glow with the least grappling. If you’re fond of gold plants, you’ll find this golden nugget a treasure.”
  • Prostrate Japanese plum yew (Cephalotaxus harringtonia ‘Prostrata’): This stunning deer-resistant evergreen satisfies the long-held desire of Southern gardeners for a yew that will thrive in hot, humid weather. Japanese plum yew is a slow grower, but don’t let that deter you from adding it to your garden. It thrives in a wide variety of soils but is happiest when it is moist and well-drained. At maturity this prostrate version reaches 2 to 3 feet in height and 3 feet in diameter. Allow plenty of room; it likes to spread! The Japanese plum yew has dark green linear flat-leafed needles like its Taxus namesake and sports striking lime-green new growth in the spring.

 Article written by Janet Moore, Extension Master GardenerSM Volunteer.

Read more
Plant Files by NC State Extension
Violet (Viola labrodorica)
Dwarf mondo grass (Ophiopogon japonicus)
Creeping thyme (Thymus serpyllum)
St. John’s wort or Aaron’s beard (Hypericum calycinum)
Prostrate Japanese plum yew (Cephalotaxus harringtonia ‘Prostrata’)

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Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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