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Trees

What’s THAT Evergreen? Can I grow it?

December 16, 2022

 

Evergreens in the landscape

‘Tis the season that evergreens are on display. Not only as wreaths, swags, and holiday trees, but in our landscapes. As autumn leaves fade and fall, the evergreens that remain gain our attention and appreciation. Although evergreen conifers can be great assets to our gardens, some are more suitable than others.

Evergreen conifers
There are many types of evergreen conifers you’ll see in local landscapes. These include members of the pine family (Pinaceae):

White pine bud or candle in spring_Lal Beral_CC BY-NC 2.0_Flickr
White pine needles with bud or candle
      • cedars (Cedrus),
      • firs/spruce (Abies, Picea),
      • hemlocks (Tsuga),
      • and pines (Pinus)

the cypress family (Cupressaceae):

      • arborvitae (Thuja),
      • Chamaecyparis,
      • Cryptomeria,
      • Cunninghamia,
      • Hesperocyparis,
      • junipers (Juniperus),
      • and hybrids such as Leyland cypress (x Hesperotropsis leylandii)

and the yew family (Taxaceae):

  • Cephalotaxus,
  • Taxus,
  • and Torreya.

Identifying evergreens
If you admire a particular evergreen in the forest, a neighbor’s yard, or even a live holiday tree, the first thing to do is identify it. With evergreen conifers the “leaves” provide important clues:

  • Members of the Pine and Yew families have needles—Yew family needles tend to be broader than pine family needles.
  • Most members of the Cypress family have either awl-shaped leaves or scales.
Arborvitae needle scales
Chamaecyparis needles
Yew needles
White pine needles and cones

Cones and bark offer other important clues to confirm conifer ID. See, below, for helpful sources.

Choosing evergreens for your landscape
Once you’ve identified interesting evergreens, decide where and how they will fit into your existing plantings.
General considerations. Evergreens provide shade and cover all year round, which can be a good thing, but before planting think about:

  • mature size—both height and width
  • impact on views
  • shape—how will the shrub or tree change in shape over its lifetime and how much effort will it take to maintain it?
  • avoiding a monoculture—planting several of the same plants—because if disease or pests attack even one, the planting may fail.
Hemlock Woolly Adelgids

Insects, diseases, and other problems. Not all evergreens that can survive in our area are good choices —including some natives—even if they will fit your homesite.

  • Some popular Cypress family choices— arborvitae, Japanese cedar (Cryptomeria japonica), and Leyland cypress—have many known problems (read more at: https://pdic.ces.ncsu.edu/decision-guide-for-cypress-problems/). Leyland cypress is considered so problematic it is not recommended for planting anywhere in North Carolina!
  • In the Pine family, hemlocks need protection from hemlock woolly adelgids, and firs and spruce are subject to other insect and environmental problems, as are some pines (see details, below).
  • Yews, too, have insect, disease, and siting issues to consider (links below).

What about choosing a live holiday tree? Many trees are sold live in containers or wrapped in burlap for planting outdoors after indoor display for the holidays. North Carolina Forestry specialists note that of the most common holiday trees sold live, only a few are adapted to mountain environments:

  • white pine (Pinus strobus),
  • Fraser fir (Abies fraseri),
  • blue/Colorado spruce (Picea pungens),
  • Norway spruce (Picea abies), 
  • and white spruce (Picea glauca).

Note that other live trees sold for the holidays—Arizona cypress (Hesperocyparis arizonica), and Virginia pine (Picea glauca)—are better suited to transplanting in Coastal and Piedmont regions of the state.

Fraser fir and Blue/Colorado spruce

Unfortunately, even the mountain-adapted species have limited success planted in home landscapes. Fraser fir is often afflicted with balsam woolly adelgid. White pine and spruce trees do best in cooler sites, protected from winds. White pine does well in altitudes up to 3,000 feet; spruce species seem to do better at higher elevations; our only native spruce species, red spruce (Picea rubens), naturally occurs only above 4,500 feet!

Which native evergreens are good choices? Some native evergreen trees that do well in the mountains and are valuable to wildlife are:

  • eastern red cedar (Juniperus virginiana), which provides cover for wildlife, fleshy fruit to eat, and is a host for butterfly larvae,
  • shortleaf pine (Pinus echinate), which provides cover, seeds to eat, and is a host for butterfly larvae,
  • white pine, which provides cover and seed,
  • and loblolly pine (Pinus taeda), which provides cover and seed, and is a host for butterfly larvae.

Article written by Debbie Green, Extension Master GardenerSM Volunteer

For more information:

Identification:

Leaves:

https://www.trianglegardener.com/tips-to-identifying-conifers-in-the-landscape/

https://smallfarms.cornell.edu/2019/02/arent-they-all-just-pines-how-to-id-conifer-trees/

https://herbarium.ncsu.edu/tnc/vis_gymno.htm

Cones and bark: https://dnr.maryland.gov/wildlife/Documents/Basic_conifer_key.pdf

Evergreen conifer problems:

Overview: https://content.ces.ncsu.edu/insect-and-related-pests-of-shrubs/pests-of-conifers

Cypress family: https://pdic.ces.ncsu.edu/decision-guide-for-cypress-problems/

Pine family:

Pines: https://content.ces.ncsu.edu/pine-pest-management-calendar

Hemlocks: https://savehemlocksnc.org/info-for-landowners/landowner-treatment/

Blue/Colorado spruce: https://henderson.ces.ncsu.edu/2020/07/colorado-blue-spruce-issues/

Yew family:

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/visual-guides/yew-problems

https://www.uky.edu/Ag/Entomology/treepestguide/taxus.html

Live holiday trees: https://content.ces.ncsu.edu/selection-and-care-of-living-christmas-trees

Landscaping with native plants: https://content.ces.ncsu.edu/landscaping-for-wildlife-with-native-plants

 

 

 

 

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Categories Trees Tags conifers, evergreen, garden planning, Identify, landscape planning, native plants

Pest Facts: Hemlock Woolly Adelgid (HWA)

October 28, 2019

Just visit a Western North Carolina forest to see how much destruction this non-native invasive insect pest has caused—and is still causing—on the native Carolina hemlocks (Tsuga caroliniana) and Eastern hemlocks (Tsuga canadensis)! After our recent rains, this is a good time to treat your hemlocks if you see a white cottony substance on your hemlocks.

Hemlock Woolly Adelgid

History

  • HWAs were discovered in Shenandoah National Park in northern Virginia in 1988, likely when crawlers clung to the legs and feathers of migrating birds, such as the black-throated green warbler and solitary vireo that visit or nest in hemlock trees.
  • HWAs were discovered on hemlocks in North and South Carolina in late 2001 and early 2002.

HWA (Adelges tsugae) Life Cycle:

  • HWAs hatch from eggs and then go through a crawler stage—almost invisible to the naked eye. These crawlers cannot fly on their own but can drift in the air from tree to tree, and cling to the legs and feathers of migrating birds.
  • After settling on host trees, the HWAs insert a bundle of mouthparts at the base of a needle and spend the rest of their lives—a few months—sucking nutrients out of the tree.
  • The name “woolly” comes from the fact that adult HWAs are covered with a protective white fluff once they settle.
  • The HWA goes through two generations a year (one in March and one in October in Western North Carolina) and each female—even without being fertilized by a male—can lay between 100 to 300 eggs.
  • This reproductive process is called “parthenogenesis”—the offspring are genetically identical clones of their mother.

Controls

Chemical: Registered pesticides containing imidacloprid or dinotefuran are the most effective chemical treatments for control of HWAs. These are applied as a soil injection or trunk spray. These insecticides are water soluble and move into the tree’s vascular system along with water. Dinotefuran has a faster uptake, but imidacloprid has a longer residual protection. Control of HWAs using imidacloprid can last for 4-5 years. Dinotefuran may require retreatment within 2 years.

Biological:

The species that has so far shown the most promise as a biological control agent is Laricobius nigrinus, a predator beetle native to the Pacific Northwest. L. nigrinus is active from October to March; both adults and larvae will consume all stages of HWAs: eggs, nymphs and adults.

After exhaustive evaluation in quarantine labs, it was cleared by the USDA for use as an HWA biocontrol in the eastern United States in 2000 and has been released in NC since 2003.

Original Article by Glenn Palmer, Extension Master GardenerSM Volunteer, Revised by Bob Wardwell, Extension Master GardenerSM Volunteer

Hemlock Restoration Initiative https://savehemlocksnc.org/

National Park Service Great Smoky Mountains Hemlock Woolly Adelgid

https://www.nps.gov/grsm/learn/nature/hemlock-woolly-adelgid.htm

University of Massachusetts HWA Fact Sheet https://ag.umass.edu/landscape/fact-sheets/hemlock-woolly-adelgid

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Categories Invasive Insects, Pest Management, Trees Tags Biological Control, Hemlock Woolly Adelgid, insects, pest control, trees

What Are Those Purple Flowering Trees—Native Redbud or Invasive Paulownia?

March 9, 2018

Are you seeing signs of spring? After the bold yellow forsythia blooms, purple-flowering trees will soon brighten our yards and hillsides. What are those lovely trees? In March and April in Western North Carolina, these are most likely the native eastern redbud (Cercis canadensis). By late April or May, you’ll see larger purple flowers on the invasive Princess tree (Paulownia tomentosa). 

Eastern redbud_Cercis canadensis 'Silver Cloud'_UGA College of Ag_CC BY-NC 2.0_Flickr
Eastern redbud tree (Cercis canadensis)

About Redbuds
The eastern redbud is a small deciduous tree—15 to 30 feet tall and 15 to 25 feet wide—native to North America, ranging as far north as Canada, south as Florida, and west to Texas.

The pink to reddish-purple flowers emerge in early spring on old branches and trunks, before the leaves. After blooming, the heart-shaped leaves emerge and mature to a dark green, turning yellow to yellowish orange by fall. The trees produce clusters of green seed pods that look similar to snow peas, but brown when mature.

In the wild, eastern redbud occurs as an understory tree, preferring moist, well-drained soil, but adaptable to a range of soil conditions, and hardy from USDA zones 4 to 9.  The trees will tolerate full sun and both alkaline and acidic soils. In WNC, the trees are usually more numerous on south-facing slopes with more sunlight. They are fire-tolerant and will sprout back from the roots after a fire.

Eastern redbud_flowers_reclaimednj_CC BY-NC 2.0_Flickr
Eastern redbud flowers
Heart-shaped leaves; Eastern redbud (Cercis canedensis)_heart-shaped leaves_Kerry Wixted_CC BY-NC 2.0_Flickr
Eastern redbud heart-shaped leaves
Eastern redbud (Cercis canedensis)_seed pods_NatureServe_CC BY-NC 2.0_Flickr
Eastern redbud seed pods

Uses
Redbud nectar attracts butterflies and hummingbirds. Pollen feeds honeybees. Birds and squirrels may feed on the seeds. Redbuds are in the pea family—their edible flowers taste like peas, making them a colorful and tasty addition to a spring salad—but only if the trees are untreated with pesticides. Some Native Americans and folk healers use the bark and roots to produce teas and tinctures to treat various ailments. 

Diseases and Pests
These beautiful trees are usually free of serious disease and pests, but are relatively short-lived, typically declining from disease after twenty years. The most common culprit is the fungal disease, Botryosphaeria canker, which can encircle the branches, effectively cutting off the water supply to the leaves, leading to branch drop. Keep plants as healthy as possible by watering regularly during dry periods and pruning out diseased branches with disinfected tools. Verticillium wilt, another serious fungal disease, blocks the tree’s vascular system from taking up water and nutrients. Leaf anthracnose and other leaf spot diseases may affect the tree’s appearance but not its overall health.

Insects that feed on redbuds include treehoppers, caterpillars, scales, and leafhoppers. For serious infestations, contact your local Extension office for treatment options.

Cultivars
Eastern redbuds are lovely native trees that are valued in our landscapes. Several redbud varieties are available. Check out some of these selections to see what strikes your fancy.

‘Alba’ (white flowers)
‘Appalachian Red’ (hot pink flowers)
‘Covey’ (dwarf weeping habit)
‘Flame’ (double flowers, seedless)
‘Forest Pansy’ (purple foliage, pink flowers)
‘Ruby Falls’ (purple foliage, weeping habit)
‘Silver Cloud’ (variegated green and white foliage)
‘Hearts of Gold’ (golden foliage)

Avoid the Paulownia!
The Paulownia or Princess tree also blooms in spring with panicles of purple flowers. Paulownia was introduced in the mid-1800s as an ornamental landscape plant. It is now considered an ecological hazard, especially to Linville Gorge and along I-40 near the Tennessee state border. Princess trees are invasive everywhere in our area and are not recommended as landscape plants. Eliminate volunteers before they establish.

Paulownia tomentosa_Princess tree_in flower_James Gaither_CC BY-NC-ND 2.0_Flickr
Paulownia tomentosa tree in flower
Paulownia tomentosa_Princess tree_huge leaves_James Gaither_CC BY-NC-ND 2.0_Flickr
Paulownia tomentosa tree, huge leaves

Article written by Barbara Hayes, Extension Master GardenerSM Volunteer.

More information
Eastern redbud plant description
by NC State Extension

Eastern Redbud Plant Fact Sheet
by U.S. Department of Agriculture

Paulownia or Princess tree plant description
by NC State Extension

What Are the Purple-Flowered Trees? Paulownia and Oriental Wisteria
by Alison Arnold, Extension Agent, NCSU

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Categories Trees Tags Eastern redbud tree, Paulownia tomentosa, Paulownia tree, princess tree

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