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

Polar Express Sunbelt Rose Big Winner At 2016 Biltmore Gardens Rose Trial

Posted by Hugh on October 29th, 2016

Polar Express Sunbelt Floribunda (Photo: The Biltmore Company)

‘Honeymoon Arborose’ (photo: The Biltmore Company)

If you grow roses in the U.S. Mid-South region, the historic Biltmore Gardens in Asheville, NC is key source for discovering what varieties you should be growing.

Recently, a jury of world rose experts selected the winning roses in the 2016 Biltmore International Rose Trials. Since 2011, Biltmore’s historic Rose Garden has been home to the trials in which more than 150 varieties from growers and breeders worldwide have been planted and cared for by Biltmore’s horticultural team.

Polar Express Sunbelt, a fluffy white rose bred by Kordes, took the top award: the George and Edith Vanderbilt Award for Most Outstanding Rose of the Trials.

In addition to winning the Best in Show Award, Polar Express Sunbelt won the Edith Wharton Award for Best Floribunda, and the William Cecil Award for Best Growth Habit.

Additional winners this year were:

Honeymoon Arborose, bred by Kordes, won the Gilded Age Award for Best Climber and the Lord Burleigh Award for Most Disease Resistant
Double 10, bred by Ping Lim, won the Pauline Merrell Award for Best Hybrid Tea
The Lark Ascending, bred by David Austin Roses, won the Chauncey Beadle Award for Best Shrub

Each trial lasts two years and a permanent jury judges the roses four times per year. This year’s final round of competition started with 31 entries planted in 2014 from Canada, the U.S., France, Ireland, Great Britain and Germany. Competing roses are evaluated for overall health and rigor; fragrance; disease resistance; and ability to repeat bloom.

Biltmore’s Rose Garden receives Award of Garden Excellence
Biltmore’s rosarian Emily Wilson and past American Rose Society president Jolene Adams unveiled an award in honor of Biltmore’s historic Rose Garden: the World Federation of Rose Societies Award of Garden Excellence. Biltmore’s rose garden is one of only 10 gardens in the United States and 62 worldwide to receive this honor.

Conifers for Small Garden Spaces

Posted by Hugh on October 27th, 2016

Dwarf Blue Colorado spruce with other conifers

Abies koreana ‘Silberlocke’ at Atlanta Botanical Gardens

Some properties can not accommodate the enormous size of tall evergreen trees. In the world of conifers, a select number of genetically dwarf species and varieties are better fits for small spaces. Most evergreens are sun lovers and require a well-drained soil. Mulching around trees and shrubs also benefits to conserve soil moisture and keep roots cool.

Here is a collection of conifers that you should try in your landscape/garden. Mr. Duane Ridnour at Beaver Creek Nursery in Knoxville, TN and Michael Balogh, owner of Mountain Meadows Nursery in Weaverville, NC, assisted in developing this list. Any list is never complete and additional numbers of excellent dwarf conifers could be added.

‘Silberlocke’ Korean fir (Abies koreana) -best grafted on Abies firma rootstock in clay soils

Shrub selections of Deodar cedar (Cedrus deodara) -two selections: ‘Feelin’ Blue’ – spreading evergreen with bluish-green needles; ‘Divinely Blue’ -dense multi-stemmed evergreen shrub with a distinctive and refined pyramidal form. Zones 6 (with protection) – 9)

Shrub selections of Japanese cedar (Cryptomeria japonica) – ‘Gyokuri’ – 18 feet high intermediate form or ‘Elegans Nana’ (compact shrub form).

‘Sester’s Blue’ Colorado spruce (Picea pungens var. glauca) is a dense multi-stemmed evergreen shrub with a distinctive and refined pyramidal form; retains its silvery blue needle foliage color through the winter (zones 3-7).

Shrub selections of Bosnian pine (Pinus leucodermis), formerly P. heldreichi, comprises a number of excellent dwarf selections (USDA hardiness zones 4-8); thrives at home in dry limestone soils. Dwarf selections include ‘Compact Gem’, ‘Irish Bell’, and ‘Schmidtii’.

‘Bergman’ Japanese White Pine (Pinus parviflora ‘Bergman’) is a compact upright shrub or small tree with slightly twisted blue-green needles.

‘Thunderhead’ Japanese black pine (Pinus thunbergii ‘Thunderhead’) is an 8-10 feet high shrub with superior disease and insect resistance.

‘DeGroot Spire’ Eastern Arborvitae (Thuja occidentalis ‘DeGroot Spire’) grows about one-third the size of popular cultivar Emerald®.

‘Roger’s Aurea’ Western arborvitae (Thuja plicata ‘Rogers Aurea’) grows 4 to 6 feet tall and wide with bright golden foliage (zones 5-9).

‘Van den Akker’ Alaskan cedar (Xanthocyparis nootkatensis ‘Van den Akker’) is a narrow vertical form that grows less than half the height of the species.

Most conifers listed here are available for regional nurseries specializing in dwarf conifers. Many large west coast U.S. nurseries ship to independent garden centers across the country.

Eastern White Pine Losses Continue

Posted by Hugh on October 24th, 2016

Eastern White Pine (Pinus strobus)

Environmental and pathogenic problems continue to take their toll on Eastern White Pine (Pinus strobus). This valued landscape and lumber tree is native in the Eastern U.S. and Canada (USDA zones 3-8). Climate change is likely contributing to recent losses of white pines due a number of serious disease and pest problems that are reducing tree numbers.

Pests:

A decade ago, pine beetles devastated large populations of white pines in the Southeastern U.S. Injury symptoms closely mimicked drought injury. Beetles lay their eggs and larvae tunnel into the branch wood. Needles turn straw brown, often showing up at tops of trees. Summer droughts have made infestations more severe.

White Pine weevil is another serious pest. Weevil larvae feed on the sapwood and kill the top growth (leaders). A common symptom is presence of pearl white resin leakage on limbs.

Pine Sawfly larvae (caterpillars) can cause rapid defoliation of branches if left unchecked; they feed in groups on the needles.

Pine needle miner larvae feed inside needles causing them to turn yellow and dry up.

Two kinds of scale insects feed on needles: pine needle scale (white, elongated scale) and pine tortoise scale (brown colored). Horticultural light oils are very effective applied in late winter.

Diseases:

White Pine Blister Rust. In some areas of the U.S., farmers and home gardeners are prohibited by law to grow black currants, which are alternate hosts for this disease. Red currants should not be grown within 300 feet of white pines. Infected branches may be pruned off. Some varieties of white pine are resistant to this disease.

White Pine Decline describes the slow decline of pine trees. Needles turn pale green, shrivel, and ooze sap. The entire tree is usually affected and mimics a root system. Causes seem to be a combination of environmental stresses, and shows up worse in dry clay soils. Tree usually does not recover and dies within 4-6 weeks.

Additionally, white pines are susceptible to urban air pollutants including ozone and road salt. Limbs are susceptible to ice breakage.

‘Midwinter Fire’ Dogwood Brightens Up The Winter Landscape

Posted by Hugh on October 21st, 2016

Cornus sanguinea ‘Midwinter Fire’ in November

Winter Scene at Biltmore Estates in Asheville, NC

Bloodtwig dogwood (Cornus sanguinea), indigenous to Europe and Asia, is an upright branched, round-topped, spreading deciduous shrub (USDA hardiness zones 5 to 7). In the wild the species matures to 8-15 feet in height and spread.

Its common name “bloodtwig” is misleading. Winter wood on 1-2 year old branches is not red. Instead, winter stems turn a striking orange-yellow at the base with reddish twigs on the tips. Fall leaf color is golden yellow some years and a blah red in others. The 3-inch long broad-elliptic to ovate leaves in spring and summer are dark green above and grayish, covered with tiny hairs underneath.

If your goal is to introduce more vibrant color into the winter landscape, select the cultivar ‘Midwinter Fire’. This compact form grows only 5 to 6 feet tall and wide after 3-4 years. It flourishes in any soil type that is well-drained and in full to partial sun. Brightest stem color occurs on young 1-2 year old wood. Annual pruning is an absolute! and take care of this chore in early spring. Every 3-4 years rein in the entire shrub by cutting back all stems to the ground in early spring (renewal pruning). Bloodtwig dogwood tends to ramble and you will want to remove root suckers to check spread of shrub.

Flat white 2-inch wide cyme flowers are not sensational but do attract numerous butterflies and other pollinators. Up close, flowers emit a stale fragrance in May to early June. In August-September blue-black fruits (1/4 inch wide drupes) form and later attract winter feeding birds. Fall color can be average yellow some years and bright orange-yellow in other years. Summer foliage is green and remains blemish-free.

Utilize as a specimen shrub or group 3-5 together for color impact in fall and winter as a hedge or short privacy barrier. Redtwig is a great choice for attracting wildlife, particularly to rain gardens. No disease or insect problems trouble bloodtwig dogwood and deer leave it alone.

Happidaze® Sweetgum Produces No Gumballs

Posted by Hugh on October 18th, 2016

‘Happidaze’ Sweetgum on Median Strip In Johnson City, TN

Sweet gum (Liquidambar styraciflua) is a low-maintenance deciduous shade tree. The species is native from Connecticut to Florida and west to Missouri and south to Texas and Mexico (USDA hardiness zones 5 – 9). A popular landscape shade tree, it typically grows to 60 to 80 feet tall with a straight central trunk. A young tree is pyramidal in outline, but an older tree gradually forms an oval to rounded canopy.

Most sweetgum cultivars is notorious for producing “gumball” fruits which are hard, spherical, bristly fruit clusters to 1 ½ inches in diameter. Happidaze® is a fruitless cultivar. The absence of messy fruits littering lawns and walkways all fall and winter long sets Happidaze apart from most sweetgum varieties.

Lustrous, long-petioled, deep green leaves (4-7 inches across) with toothed margins emit a sweet fragrance when bruised. Fall color is a rich red maroon. Yellow-green flowers appear in spherical clusters in April-May and offer no significant landscape value. Branchlets may have distinctive corky ridges.

Sweetgum is easily grown in moist, well-drained soils. The tree prospers in full sun and falters in shade. It prefers a slightly acidic soil pH between 5.8 – 6.5; leaves frequently turn chlorotic (yellow) in high alkaline pH soils. Feed in early spring with a slow-release fertilizer such as Osmocote® or Nutrikote®. Refresh the mulch cover around the tree every spring.

Sweetgum rarely succumbs to serious insect or disease problems. Leaf spot diseases, webworms, caterpillars, borers and scales may be occasional problems. Iron chlorosis, a lack of available nutrient iron, may occur in alkaline soils.

Sweetgum is excellent shade, lawn, park or street tree. Give this large tree room to grow and it will reward you with lots of cooling summer shade and glorious fall color for many decades.

Special note: Sweetgum cultivars ‘Rotundiloba’ (medium size tree) and tall narrow ‘Slender Silhouette’ are two other seedless (no gumballs) forms.

Fascinated By Praying Mantis

Posted by Hugh on October 15th, 2016

Praying Mantis -Chinese on hood of car (photo by Dr. Frank Hale)

Praying mantis (Photo by Dr. Frank Hale, Univ. of TN Entomologist)

Carolina Praying Mantis (often written “mantid”, referring to family Mantidae) (Stagmomantis carolina) is the only species of praying mantis native to the U.S. However, about 20 species are found in the U.S. Most ubiquitous here is the European mantis (M. religiosa). Chinese Praying Mantid (Tenodera aridifolia) is the largest species by size in the U.S., measuring almost 4 inches in length. They’re easily purchased in kits for school age children who raise them as a pet or study mantids as part of a nature project.

Praying mantids are typically green or brown and can disguise themselves as a dried slender leaf or twig. Praying mantids are named for their prominent front legs, which are bent and held together at an angle that suggests the position of prayer. Mantids are formidable predators. They have triangular heads poised on a long “neck,” or elongated thorax. They can turn their heads 180 degrees to scan their surroundings with two large compound eyes and three other simple eyes located between them. No other insect can do that.

Praying mantids lie in wait to capture their quarry, be it moths, crickets, grasshoppers, flies, and other insects. An adult female sometimes eats her mate after mating. Mantids snare their prey with their front legs with rapid reflexes. Their legs are further equipped with spikes for capturing and pinning their prey.

Females regularly lay hundreds of eggs in a protective egg case (ootheca), and nymphs hatch looking much like tiny versions of their parents. People may be shocked to find several hundred hatchlings coming from egg cases attached to firewood that was brought indoors.

Larger species of mantids can catch and eat lizards, frogs, and even tiny birds like hummingbirds. Mantids don’t discriminate between good bugs and bad bugs such as beneficial bees, lacewings and moths. To turn the tables, bats feed on praying mantids.

Try Popcorn Cassia For Its Lush Tropical Look

Posted by Hugh on October 12th, 2016

Senna (Cassia)

Flowering of popcorn plant

Big and bold is this tropical annual (USDA hardiness zones 9-11), known by several names including popcorn or peanut butter cassia (Senna didymotrya), formerly Cassia didymotrya. Popcorn plant is a legume family (Fabaceae), indigenous to tropical Africa. It is also been utilized as a cover crop or green manure crop in some areas of the world. It thrives where summers are long, hot and humid in the U.S.

Popcorn cassia grows 6-12 feet tall in temperate climates by the end of summer. In zone 6 (northeast Tennessee), expect 6 -7 feet. Direct seed into the garden in early May after danger of frost has passed. Growth rate ramps up as outdoor temps rise.

Popcorn cassia blooms from late spring into early fall and is often utilized as a garden accent plant for its tall flower spikes and lush tropical foliage. Bloom buds are jet black and pop open with showy yellow flowers. Each pinnately compound leaf may grow to 18 inches long, arranged in pairs of oval 8-18 leaflets that are up to 3 inches long. Plant(s) set in large containers grow a lot smaller and flower less.

Flower spikes may stand up to one foot tall. Each flower is ½ to 2 inches wide with showy prominent stamens. Opinions about floral fragrance can be quite subjective. Some say that the flowers smell like peanut butter. Flat 3-5 inch long brown pods form after flowering. Each may contain up to 16 shiny flat bean-like seeds.

Popcorn cassia grows best in full sun and in moist, well-drained soil. By mid-summer, plant is highly drought tolerant. Otherwise, irrigate and fertilize regularly to push growth and flowering. Use a liquid fertilizer such as Miracle-Gro™ or Daniels™.

Prune to keep plant more compact, but flower numbers will be less. Plant has no significant disease or pest problems and generally is not troubled by deer.

In late winter start new plants indoors from seed collected last fall. Pre-soak seed in water for 24 hours prior to sowing to improve germination.

Glenna Schaefer, garden expert at Kingwood Center in Mansfield, Ohio, tells me that two species, Senna hebecarpa and S. marilandica, are native to Eastern North America and are quite hardy there (zone 5).

Monarch Tagging Program*

Posted by Hugh on October 9th, 2016

"Tagged" Mnarch Butterfly at NC Arboretum in Asheville, NC

“Tagged” Monarch Butterfly at NC Arboretum in Asheville, NC

*Blog is guest authored by Joy Stewart, University of Tennessee Master Gardener. She lives in Bristol, TN.

For such a small creature, weighing in at only half a gram, the Monarch butterfly has almost more remarkable facts and puzzling mysteries attached to it than one can count. No other butterfly in the world migrates like the Monarchs of North America.

Since they cannot survive cold weather, Monarchs must travel to warmer climates in winter. Monarchs west of the Rocky Mountains travel to the California coast. Monarchs east of the Rockies travel to the mountains in Mexico. They fly up to 3,000 miles, much farther than all other tropical butterflies. Since each individual butterfly only makes the trip once, butterflies heading south in the fall are the great great grandchildren of those that left their winter roosts the previous spring. Yet returning butterflies fly in masses to the same winter roosts, often to the exact same spot they left four generations ago.

Monarch Watch is a non-profit program dedicated to protection of Monarch butterflies through education, conservation and research. It is based at the University of Kansas, Lawrence, KS. Their activities include a Monarch tagging program whose purpose is to trace a butterfly from its point of capture to its point of recovery. Tagging data are used to determine pathways that butterflies take during migration, the influence of weather on migration, and Monarch survival rates.

Individuals can order tag kits from Monarch Watch, which include instructions on how to safely net Monarchs, how to apply the tags, and how to record and report your data. Tagging begins in late August in all regions of the US, and most data are collected in September and early October.

Even if you don’t tag a butterfly yourself, you can participate by reporting butterflies that you have spotted with a tag. Each tag contains an ID composed of letters and numbers plus a phone number and e-mail address for making your report.

Peak Monarch migration southward from the mid-Atlantic states occurs from September 18 through October 1. A simple accurate way to remember these dates is to watch for New England Aster and goldenrod to start blooming and you will know Monarch migration is underway.

Grow Something Different With Redvein Maple

Posted by Hugh on October 7th, 2016

Acer rufinerve late summer foliage

Snake bark trunk exhibited at Biltmore Estates, Asheville, NC

In the world of maples the snakebark trait is unique. Redvein maple (Acer rufinerve) from Japan belongs in this maple category (USDA hardiness zones 5-7). It is a small to medium deciduous tree or large shrub with an upright branching framework. A young tree starts off slowly and may grow only to 12-15 feet in 10 to 12 years. The species matures to 30 feet tall and 20 feet wide.

As spring season approaches, dormant buds turn red, swell, and 3- to 5-lobed green leaves emerge. Autumn foliage may turn yellow, burnt orange, or purple depending on the year and locality. Autumn leaf colors are best where soil moisture has been plentiful and the tree is grown under partial shade.

Raceme flowers run about 3 inches long bearing the winged samara seeds that ripen in fall. The species name rufinerve refers to the rusty red hairs along the leaf vein axils which slough off by mid-summer. The main trunk is green with gray-white striations

The cultivar ‘Winter Gold’ displays a bright yellow bark with tiny dark specks along the main trunk and main branches. Summer and fall bark is greenish yellow and is brightly yellow in winter. Like the species, Winter Gold prefers partial shade and moderate soil moisture. Enjoy as a specimen against an evergreen shrub background or plant nearby a patio for year-round viewing.

As previously stated, redvein maple grows best in a well-drained, moist, compost-rich, moderately acidic soil, and in partial sunlight. It struggles in full sun and in dry soils. Newly-planted and young trees should be kept mulched and adequately watered during extreme summer dry spells. Established trees are moderately drought tolerant and have few disease and pest issues. Pruning is rarely necessary except to develop a good central leader on a young tree.

Redvein maple and the Winter Gold cultivar are available from on-line mail order nurseries.

Blue Lyme Grass Adapts To Almost Any Surroundings

Posted by Hugh on October 4th, 2016

Leymus arenarus planted at Atlanta Botanical Gardens

Blue Lyme Grass (Leymus arenarus ‘Blue Dune’) is a vigorous spreading cool season grass (USDA Hardiness zones 3-9). It is native to the coasts of northern and western Europe. A closely related species, L. mollis, is native to the northern coasts of North America.

Blue lyme grass is a stand out because of its beautiful steel-blue foliage. Atlanta Botanical Gardens has sited it in woodland setting under filtered sunlight while the Dallas Arboretum grows it under full hot Texas sun. It will rapidly fill in hot arid places such as near hot concrete walkways and driveways.

‘Blue Dune’ is a standout selection with steel blue foliage. Clumps average 2 – 3 feet high and spread. In mid-summer arching powder blue flower spikes (inflorescences) emerge. Some gardeners may opt to remove the flowers to accent foliage only. It is also very tolerant of salt spray and drought.

Lyme grass is a spreading cool season perennial grass in full sun or partial shade. Foliage is evergreen into the lower 20s. Plants grow equally well either full all-day sun or under several hours of moderate shade. Practice low soil fertility as this grass can become too aggressive. It tolerates a wide range of soils from wet to dry. It tends to be less aggressive in dry, clay soils and foliage becomes more silvery blue in color.

Landscape Use: Lyme Grass can be used along woodland borders, in mass plantings, in containers or planters, as a border or edger, around decks, swimming pools, and other outdoor living areas, in landscape beds or islands, to stabilize steep slopes and sand dunes. It is resistant to deer, rabbits, drought, insects, diseases, mildew, heat and butterflies are attracted to its flowers.

Mow off old foliage in late fall or early spring to refresh the planting. Clumps are easily divided at this time.

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*Blog is guest authored by Joy Stewart, University of Tennessee Master Gardener. She lives in Bristol, TN.

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