What Grows There :: Hugh Conlon, Horticulturalist, Garden Advisor, and Photographer

Pest Alert: Deep Freeze Negatively Impacts Hemlock Adelgid Populations in the Smokies

Posted by Hugh on January 12th, 2018

Hemlock adelgid

GOOD NEWS! The recent cold snap is having a negative impact on the invasive hemlock wooly adelgids in the Smokies. Since 2002 this insect has killed millions of hemlock trees in the U.S. Biologists in the Great Smoky Mountains report that the recent spell of frigid temperatures has killed off overwintering hemlock adelgids.

Over 15 years ago, the hemlock woolly adelgid (HWA) invaded the Great Smoky Mountains National Park. This tiny Asian insect has killed millions of hemlock trees in the Eastern U.S. The pest gets its name from the white woolly coating that covers and protects the nymphs while they feast on hemlock trees.

Wooly adelgids complete a lot of their life cycle over the winter months. The severe dips in temperatures this winter are negatively effecting populations in the Northern areas of the U.S. and Canada. Insect mortality occurs when temps go down to 4 – 5°F.

The hemlock-killing bugs had been rebound the last couple of winters. A similar deep freeze back in 2014 also penetrated the insects’ woolly protection. “The big ‘polar vortex’ blast in 2014 and 2015 really helped us out with the adelgid. We had those prolonged weeks where the temperature was below zero in the higher elevations and killed a lot of them,” says NPS forester Jesse Webster.

Last year’s drought saw big population increases in HWA. “We really can benefit from some hard freezes in dry weather. Snow and ice can insulate insects. When they are directly exposed to the extremely cold air, that’s when their mortality rates are really high” says Webster.

Credit: this information originated from a news report from WBIR-TV in Knoxville, TN and has been edited.

Key Landscaping Tips

Posted by Hugh on January 11th, 2018

Hybrid rhododendron

Soil preparation

To develop a successful landscape plan, first do a walk-a-round before you start digging and planting. Record your landscape’s sun patterns, soil types, wind and water movement. This information will help you select the kinds of plants that will prosper under existing conditions.

Sun exposure shifts daily and seasonally. Observe the garden at different times to gain a better understanding of light exposures. Particularly note areas that receive full day sun or full shade. What percentage of existing trees and shrubs are deciduous and evergreen. Under deciduous shade, the fall and winter landscape may bathe in sunlight. In areas with partial sun exposure, identify where sunlight strikes an area at what time(s) of day as well as seasonally.

Soils may vary from one area of a landscape to another. Dig test holes in a variety of locations to determine the texture and color of soils. Is the landscape composed of sandy or loamy soils? Does it contain lots of clay? Soil type and drainage go hand-in-hand and impact the types of plants that should prosper in your landscape. Sandy soils drain very quickly, while clay soils are slow to drain. Many plants are also limited by soil pH, so it is a good idea to have the soil analyzed.

Water and Soil Drainage. In addition to soil type, topography and physical structures influence soil moisture. Low spots and areas surrounding downspouts tend to be wet, while the area beneath an overhang is commonly dry. Walk the garden after a rain to see where water collects and make note of seasonal rainfall patterns in your area. Do your region frequently experience seasonal drought; is your summer climate hot and humid? Are your winters generally snow covered or will ice storms damage tree branches?

Wind. Exposure to wind may vary considerably across a landscape. Some areas are likely exposed to strong winds while others may be protected by buildings, structures, or tall shrubs. For example, broadleaf evergreens such as camellias, rhododendrons, daphnes, and pieris are sensitive to drying winter winds. Understanding wind patterns will aid in positioning new plants at planting time.

Wildlife. What birds and animals are indigenous to your neighborhood? Do critters cause damage to plants? Consider deer, rabbits, raccoons, squirrels, moles, voles (field mice) which may relish your landscape and garden plants.

Common Street and Landscape Trees

Posted by Hugh on January 10th, 2018

Street tree planting of Ginkgo

Across the U.S. and Canada, city planners, landscape architects, and property owners now enjoy a wide selection of landscape trees to plant on city streets, along roadsides, and in yards and gardens. Over the past half century new and improved varieties (cultivars) are disease and pest resistant and exhibit better branching and architecture. We now know to avoid species with messy fruits or that produce excessive leaf litter. Most important is to select according to the tree size (mature height and branch spread).

Plant scientists and city arborists continue to evaluate tree selections that perform best in their areas. Below is a list of more than 50 common species that are currently planted across the U.S. THIS LIST IS NOT COMPLETE. Planting some tree species such as ash (Fraxinus), black walnut (Juglans), and callery pear (Pyrus) are on the decline because of pest and disease problems or weak branching.

Before planting a tree, reach out to local experts at nurseries and full-service garden centers or call the county/city Extension office. State universities, botanical gardens, and arboretums may also provide tree lists. Take a few minutes to look up for utility lines and telephone utility companies to locate buried lines.

List of Landscape Trees:

Japanese maple (Acer palmatum)

Norway maple (Acer platanoides)

Red maple (Acer rubrum)

Silver maple (Acer saccharinum)

Sugar maple (Acer saccharum)

Ohio Buckeye (Aesculus glabra)

Serviceberry (Amelanchier spp.)

Birch (Betula nigra)

Paper birch (Betula papyrifera)

Horsechestnut (Aesculus hippocastanum)

Northern catalpa (Catalpa speciosa)

American hornbeam (Carpinus carolinana)

Carpinus betulus ‘Fastigiata’

European hornbeam (Carpinus betulus)

Hackberry (Celtis occidentalis)

Eastern redbud (Cercis canadensis)

Yellowwood (Cladrastis kentukea)

Washington hawthorn (Crataegus phaenopyrum)

Green hawthorn (Crataegus viridis)

White ash (Fraxinus americana)

Green ash (Fraxinus pensylvanica)

Ginkgo (Ginkgo biloba)

Honeylocust (Gleditsia triacanthos)

Kentucky coffeetree (Gymnocladus dioicus)

Black walnut (Juglans nigra)

Red cedar (Juniperus virginiana)

Goldenrain tree (Koelreuteria paniculata)

Crape myrtles (Lagerstroemia x spp.)

Sweetgum (Liquidambar styraciflua)

Tulip poplar (Liriodendron tulipifera)

Southern magnolia (Magnolia grandiflora)

Southern magnolia

Crabapple (Malus spp.)

Blackgum, tupelo (Nyssa sylvatica)

Callery pear (Pyrus x calleryana)

Ironwood (Ostrya virginiana)

London plane, Sycamore (Platanus x acerfolia)

American sycamore, planetree (Platanus occidentalis)

White poplar (Populus alba)

Cottonwood (Populus deltoides)

Flowering cherries (Prunus spp.)

White oak (Quercus alba)

Bur oak (Quercus macrocarpa)

Pin oak (Quercus palustris)

Willow oak (Quercus phellos)

Northern red oak (Quercus rubra)

Black locust (Robinia pseudoacacia)

Japanese Scholar, pagoda tree (Styphnolobium japonicum)

Mountain ash (Sorbus spp.)

Japanese tree lilac (Syringa reticulata)

Bald cypress (Taxodium distichum)

Eastern arborvitae (Thuja occidentalis)

American linden (Tilia americana)

Little leaf linden (Tilia cordata)

American elm (Ulmus americana)

Lacebark elm (Ulmus parvifolia)

Japanese zelkova (Zelkova serrata)

Crypts (Cryptanthus) Are The Easiest Bromeliads To Grow

Posted by Hugh on January 7th, 2018

‘Elaine’ Cryptanthus at 2016 Philadelphia Flower Show

C. fosterianus-‘Liza-Vinzant’

Crypts (Cryptanthus spp.), members of the bromeliad family, are an ideal low care choice for house plant collectors. Currently, there are over 1200 varieties of Cryptanthus species and hybrids available today. Compare to other bromeliads, which grow in trees or rock outcropping, crypts grow in soil or rock ground. Plants prefer an airy, porous, moist soilless media favored by most tropical plants, including African violets, orchids, and ferns.

Most kinds of crypts grow in low-light conditions found in most homes. They benefit from daily misting, particularly during the winter month. Some can tolerate direct sunlight but need more frequent watering. Best foliage color is in bright diffused light source. Excessive direct sunlight may bleach out leaves or cause burn spots. Contrarily weak foliage and lose of color typical for the variety suggests that the plant needs more light. Fluorescent Gro-lights and new LED lights bring out their textured leaf color(s).

Like bromeliads, crypts make excellent office plants, in a temperature range between 60 to 85°F and tolerate temperature lows just above freezing. They will tolerate summer temperatures above 100 °F. if soil moisture and humidity are adequate. Many varieties thrive outdoors in shady areas of the garden in USDA zones 8-11. Fertilize crypts with a dilute solution perhaps ¼ to ½ package directions such as Miracle-Gro™ or Peters™. Crypts are relatively disease and pest free.

Crypts are reliable bloomers. Different species and cultivars bloom at different times of the year. Flowers are generally white although some have pink to lavender flowers.New plants are produce from offsets (pups) which form on stolons (runners) originating from the plant base. Offsets begin to develop when the mother plant initiates blooming or shortly thereafter. Many crypts make ideal hanging basket plant with the pups hanging off the pot edges.

Tree Cultivars That Do Not Produce Seeds Or Fruits

Posted by Hugh on January 4th, 2018

Aesculus x ‘Baumannii’

‘Ace of Hearts’ redbud – no seed pods

Perhaps you don’t like picking up messy fruits and seeds from your lawn in the fall and winter. Choose landscape trees that have seedless cultivars. A true seedless variety is an easy choice to avoid fruit cleanup.

Below are a few non-fruiting or seedless cultivars available at nurseries. Not all plants listed are recommended for all home landscapes. For example, avoid planting any species of ash (Fraxinus spp.) because of the threat of Emerald Ash Borer (EAB) infestaations. So do your homework before purchasing.

A few of my personal favorites include: ‘Autumn Blaze’ hybrid maple, ‘Espresso’ Kentucky coffeetree, any male ginkgo, ‘Slender Silhouette’ sweetgum, and ‘Ace of Hearts’ and ‘Don Egolf’ redbuds.

Boxelder (Acer negundo) – male cultivars ‘Baron’

Red Maple (Acer rubrum) ‘Flame’, ‘Northwood’

Silver maple (A. saccharinum) ‘Beebe Cutleaf Weeping’, ‘Silver Queen’, ‘Skinneri’

Hybrid maples (Acer x freemanii) ‘Celzam’, ‘Autumn Blaze’, ‘Jeffersred’ (nearly seedless)

Red horse chestnut (Aesculus x carnea) – Ruby, ‘Briotti’ (almost fruitless)

‘Baumann’ Horse chestnut (Aesculus hippocastanum ‘Baumannii’)

Redbud (Cercis canadensis) ‘Ace of Hearts’, ‘Flame’ (double flowered)

Chinese redbud (Cercis chinensis ‘Don Egolf’) – no seed

American persimmon (Diospyros virginiana) – male clones

American ash (Fraxinus americana) ‘Skyline’, ‘Autumn Purple’, others.

Green Ash (F. pennsylvanica), ‘Marshall Seedless’, ‘Summit’, others.

Kentucky coffeetree (Gymnocladus diocus ‘Espresso’)

Ginkgo (Ginkgo biloba), use male cultivars such as ‘Halka’, ‘Autumn Gold’, ‘Princeton Sentry’

Honeylocust (Gleditsia triacanthos f. inermis) ‘Fairview’, ‘Green Glory’, ‘Imperial’, ‘Moraine’, ‘Shademaster’, ‘Skyline’, ‘Sunburst’

Hollies (Ilex spp.) -male clones

Sweetgum (Liquidambar styraciflua) ‘Rotundiloba’, Happidaze™, ‘Slender Silhouette’

Crabapple (Malus spp.), ‘Spring Snow’ (fruitless, but fire blight and apple scab susceptible)

‘Chapparal’ Weeping Mulberry (Morus alba) ‘Chaparral’

Kwanzan cherry (Prunus serrulata ‘Kwanzan’)

Black locust (Robinia pseudoaccia ‘Frisia’)

Sassafras (Sassafras albidum)

Steps To Making Gardening Easier

Posted by Hugh on December 30th, 2017

Hydrangea arborescens ‘Incrediball’

Gomphrena

Take an inventory of your gardening time, talley up of costs, and develop a plan how to make your garden space more beautiful with less work and cost to you.

Plant Smarter Simplify! For example, in my zone 6 garden, bigleaf hydrangeas disappoint tow out of three years and they’re water hogs in the summer. Smooth (AG) hydrangeas (like ‘Incrediball’ hydrangea pictured), and Panicle hydrangeas are so much less demanding and require far less water.

Choose annuals and perennials that are pest and disease resistant, consume less water, and are self-cleaning like gomphrena (pictured), scaevola or celosia.

Some plants are poisonous to humans and pets. Rhododendrons and Oleanders are toxic to dogs and cats. Also, rethink using pesticides on lawns where pets and children play.

Use more native plants, but also include many low maintenance non-natives that are well behaved. Garden to attract more pollinators, particularly bees, butterflies and birds.

Mulch smartly to reduce watering and weeding.

Plant “waves of ground covers” such as ferns, fairy wings (epimediums), and hostas to discourage weeds and provide a tapestry of foliage and flowers.

Plant shrubs and ornamental trees that require much less maintenance. Perhaps, it is a small long blooming shrub that can enliven an area that currently takes 4-5 perennials at twice the labor.

Downsize your growing area. Plant a rain garden or prairie border. Plant more perennials than annuals.

Emphasize safety.

Don’t strain your back or knees.

Prune less by selecting slower growing compact plants.

Grow more in raised beds that are at a comfortable working height.

Choose better quality ergonomic tools.

Summary: Rethink how you garden… Redesign your outdoor living area…More seasonal color…Less maintenance…Enjoy your garden.

Deck The Halls With These Ten Festive Plants

Posted by Hugh on December 24th, 2017

Display at Biltmore Estates in Asheville, NC

Celebrate the holiday with these live plants, some of which you receive as gifts. These houseplants can stand alone or complement the festive holiday decor:

Poinsettia. No other houseplant captures the Christmas spirit more than poinsettias.
Thanksgiving/Christmas Cacti (Schlumbergera bridesii or S. truncata) – these easy to care for dependable flowering cacti (they’re really succulents) come in red, pink or white colored blooms.

Amaryllis is a bulbous plant that blooms in winter season or program to flower in any season. Large flowers available in vibrant reds, orange tones, pinks, snowy white, or bicolors.
Amaryllis + daffodils

Norfolk Island Pine. Mini-Christmas trees have become a holiday staple at garden centers. Indoors, they may grow up to 12 feet in height. They can spend summers outdoors under the shade of a shade tree.

Kalanchoes are true succulents, so do not overwater and allow excellent soil drainage. They bear lovely foliage and long lasting flowers that come in red, orange, pink, purple, yellow, white and just recently bi-colored varieties.
Cyclamen- their lovely mottled, heart-shaped leaves and red, pink, or white flowers will beautify spaces in your home or in protected outdoor areas where nightly temperatures do not drop below 37 °F.
Bromeliads – one of the easiest house plants to grow. They don’t ask for much light. Mist the air around them several days per week. Flowers are very showy and young plants (pups) form that become the “grandchildren” of your plant.
Tillandsias – which are bromeliad relatives are frequently sold as “Air Plants” because plants don’t have roots and are not potbound. All plant(s) ask for is a daily misting or weekly one hour soaking in the sink or bucket of water.
Sedums – available in pots or planted in changeable frames suitable for wall hanging either for room interiors or outdoors (hardy types).
Paperwhites – miniature white daffodil blooms are highly fragrant. Simply give plenty them of water, and you’ will be rewarded with 4 weeks of beautiful winter white blooms

During the spring-summer seasons feed most plants (not tillandsias) monthly with a weak solution of Miracle -Gro or an equivalent product. Otherwise, water plants weekly.

Five Evergreens For Small Garden Spaces

Posted by Hugh on December 21st, 2017

Thuja occid ‘DeGroot Spire’

‘Green Arrow’ Alaskan cedar

The following five evergreen shrubs are smaller versions of the larger growing species. They make a better fit in smaller urban gardens.

Gyokuryu Japanese cedar (Cryptomeria japonica ‘Gyokuryu’) is a fast-growing, broadly conical selection with coarse bluish-green evergreen foliage. The needles are highly ornamental and remain bluish-green through most of the winter in zone 6 and points south. Neither the flowers nor the fruit are of little significance. The peeling reddish bark is an added plus. After 10 years of growth, a mature specimen will measure 12 feet (4 m) tall and 8 feet (2.5 m) wide, an annual growth rate of 12 to 15 inches

De Groot Spire arborvitae (Thuja occidentalis ‘DeGroot Spire’) – is the smaller version of Emerald arborvitae™. It is a dwarf, slow-growing cultivar with an upright, pyramidal habit and twisted, scale-like, medium green foliage. De Groot Spire can reach 15-20 feet tall and 4-5 feet wide in 15-20 years.

Dawn redwood (Metasequoia glyptostroboides) -two selections:

‘Northlight’ (‘Schirrmann’s Nordlicht’) is a dwarf shrub form of dawn redwood. It forms a rounded crown of closely spaced stems. Foliage is variegated with irregular cream-white markings.
‘Little Giant’ | Little Giant Dwarf Dawn Redwood- small erect tree to 15 feet, a mini of its lovely parent, with light chocolate brown bark and feather-light deciduous needles, can grow up to 10 inches annually.

Alaskan cedar (Chamaecyparus nootkatensis) – two cultivars to choose:

‘Van den Akker´is a Northwest native that is an extremely narrow upright. It may reach over 20 feet tall while remaining only about 1 – 1/2 feet wide. It has strongly pendulous (weeping) branches are covered with scale-like blue green foliage.
‘Green Arrow’ exhibits an extremely narrow growth habit. Lateral branches hang close to the trunk. This vertical evergreen is perfect for small gardens or tight spaces.

Bald cypress ‘Peevee Minuret’ (Taxodium distichum) is an exceptional dwarf selection of our large native bald cypress. Branching of this pyramidal tree form is upright like its larger kin. Feathery, dark green, deciduous foliage (needles) turn a rust color in fall before falling. Papery, chestnut-red bark is an added winter feature. Peevee Minuret grows 5-6 feet tall in 10 years.

Poinsettias – Best Of Show**

Posted by Hugh on December 16th, 2017

Poinsettias In Greenhouse

‘Red Elf’ poinsettia (photo from NC State University, Raleigh)

This holiday season poinsettia breeders continue to give plant buyers lovely colors, patterns and shapes. Recently, at Mitchell’s Nursery & Greenhouse in King, North Carolina, Judy Mitchell got the word out about their annual Poinsettia Open House. Close to 400 people attended their openhouse and evaluated the 10,000 poinsettias, choosing which of the 79 varieties were their favorites.

Here are the results:

Top 5 Reds

Red Elf^#
Freedom Red
Jubilee Red
Christmas Feel Merlot
Majoris Red

Top 5 Whites:

White Poinsettia Tree at Biltmore Estates, Asheville, NC

1.Polar Bear

2.Premium Polar*

3.Whitestar*

4.Snowcap

5. Mars White

*Tied for 2nd

Top Pink:

Maren
Venus Hot Pink
Luv U Pink
Luv U Pink Hot
Freedom Pink

Top 5 Novelties

Ice Punch
Red Glitter
Tapestry
Ruby Frost
Orange Spice

^#Red Elf is designed for the small pot market. Plants flower early season with medium red bracts that are upright facing.

**Source: BUZZ e-newsletter, Ellen Wells editor, oublished by BallHort

Protect New Trees From Winter Sunscald

Posted by Hugh on December 13th, 2017

Newly planted tree + mulching

Tree wrapping (Photo from A.M. Leonard, Inc)

Across the northern U.S. and Canada, cold temperatures can damage many plants. Wide fluctuations in temperature can be particularly detrimental to newly planted landscape and fruit trees from late fall to early spring. Street trees are particularly susceptible.

Sun scald is described by elongated, sunken, dried, or cracked areas of dead bark, usually on the south or southwest side of the tree. On cold winter days, the sun can heat up bark to the point where cambial activity is stimulated. At dusk or when the sun is blocked by a cloud, hill, or building, bark temperature drops rapidly, killing the active tissue

Young trees, newly planted trees, and thin-barked trees (cherry, ornamental plum, crabapple, honey locust, linden, maple, and mountain ash (Sorbus) are most susceptible to sun scald. Winter pruned trees that have had their lower shade branches removed, or have been transplanted from a shady to a sunny location are also susceptible to sun scald. Older trees are rarely injured by sun scald because their outer bark is thicker.

Sun scald can be prevented by wrapping the trunk with a commercial tree wrap or any other light-colored material. The wrap should reflect the sun and insulate the bark so temps do not wildly fluctuate. Spiral white plastic bands, available at many full service garden centers, also protect against deer and rabbit browsing (nibbling) on the bark. Wrapping 3-4 sheets of newspaper around the trunk also works. Over the first two years best management practice is to remove all wrappings in the spring and reinstall in the fall. Do not leave the wrap on longer than necessary because it could trap moisture and become a haven for pests.

Newly planted thin-barked species should be wrapped for their first two winters, but some may need covering for up to five winters, sometimes more.