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

New ‘Chastity’ Ornamental Pear

Posted by Hugh on November 11th, 2019

Chastity ™ ornamental pear (Photo by Dr. Tom Ranney)

Before you totally give up on ornamental pear trees (Pyrus calleryana) as invasive, a decision that I would never argue against, take a look at the new Chastity pear. NEW! NEW! NEW! on the market is Chastity pear, a triploid hybrid that is both very ornamental and highly infertile (USDA hardiness zones 5-9).

Chastity™ Pear was specifically bred by Dr. Tom Ranney of North Carolina State University. This hardy small tree is covered with white blossoms in early spring. Chastity pear grows to 35 feet tall and 25 feet wide. Fall leaf color is a vibrant orange to red. It is also highly resistant to fire blight.

First, a little background. The U.S. Department of Agriculture (USDA) had introduced the callery pear cultivar ‘Bradford’ (in 1960). USDA stated that it is incapable of producing viable fruit (“self-incompatible”) which later proved to be untrue. The introduction of other USDA cultivars – ‘Whitehouse’, ‘Capitol’, ‘Redspire’ and ‘Chanticleer’ permitted cross pollination among the different varieties that resulted in fertile seed being produced, and results in its invasive traits.

On the good side all hybrid ornamental pears make reliable landscape trees. Trees withstands some tough environment conditions. Trees survive on poor infertile landscape sites as long as the soils are well-drained. Most varieties are short-lived, 15-25 years.

Other than invasiveness, the fruits can stains sidewalks and wood while attracting birds that further stain everything else (while spreading seed). Why is it 99.14% sterile? Researchers at North Carolina State University (NCSU) created a triploid (Callery pear is typically diploid) that is almost completely incapable of producing fertile fruit, and this trait (sterility) bred into Chastity pear is genetically stable. Thus, the new cultivar is unlikely to revert in the future.

Questions regarding branching strength of Chastity pear is not known at this time.

C

Short Forms Of Cryptomerias

Posted by Hugh on November 6th, 2019

Japanese cedar, aka Sugi or Cryptomeria, (Cryptomeria japonica) is the national tree of Japan and also flourishes in China (USDA hardiness zones 5 to 8). It is one of the most variable conifers ranging from very dwarf rounded shrubs to large tree forms with golden or contorted leaves. It tolerates hot humid summers and prefers deep, moist, rich, acidic to neutral soil in full sun.

Handsome specimen of Cryptomeria ‘Elegans Nana’

Cryptomerias is utilized as a fast growing privacy screen in many areas of the U.S. (USDA hardiness zones 5-8). The cultivar ‘Yoshino’ is highly popular, but in many landscapes, it grows way too tall @ 30-40 feet (15-20 feet wide). Shorter tree and shrub cultivars are better choices for small to medium-sized gardens (see list below). Gold needle cultivars are available but not listed here.

Cryptomerias grow straight trunks with smaller sturdy lateral branches attached. The orange red bark peels away in vertical strips. Older trees are often limbed up to display their attractive bark. The short needles often develops a purple-bronze color in climatic zones where winters are more harsh. However, needles rapidly green-up in spring.

Cryptomerias are rarely troubled by pest and disease problems. Infrequently, a fungal blight and canker may cause needle browning on scattered branches. Prune out dead, broken, or discolored foliage when observed and remove clippings from the property.

This reliable evergreen is wind tolerant, even standing up to strong storms. Needles are also salt tolerant. Upright branches stand up well to snow loads. Cryptomerias make reliable privacy screens or windbreaks.

Intermediate And Dwarf Forms:

‘Black Dragon’ –medium height @ 10-12 feet high x 6 feet wide; deep green needle-like leaves.
‘Gyokuryu’ – compact upright pyramid habit @ 10-15 feet high; dark green foliage with only slight winter bronzing.
‘Globosa Nana’ – compact shrub form 2 to 3 feet high and wide, almost ball shaped.
‘Elegans Nana’ – globose compact form to 5-6 feet high.
‘Tansu’ – 2 x 3 feet dense compact form with rich green foliage.

There Is Nothing “Minor” About These Bulbs

Posted by Hugh on November 1st, 2019

Winter aconite (Eranthus)

Companion bulbs, often called “minor bulbs”, are early signs that spring is coming. Three of the most reliable are snowdrops, winter aconites and Glory of the snow. They bloom before crocus in winter.

Winter aconite (Eranthis hyemalis) returns with floral beauty less than three months after planting. Plants poke through the ground, grow and flower 3 to 6 inches high and wide. Bright yellow cup-shaped flowers appear in mid- to late winter. Green leaves emerge as the flowers begin to fade. All evidence of their presence has disappeared by late spring, and the bulbs have gone dormant.

Pure white, nodding, bell-like snowdrops (Galanthus nivalis) often peak through the winter snow in February. Leafless 3-4 inch stems support individual flowers. Plants grow only 4-6 inches high with 2-3 strap-like leaves.

Glory-of-the-Snow (Chionodoxa forbesii) is so-named because, in northerly areas, their bright blue six-petalled flowers poke up through the snow in the winter. Bulbs and seeds often spread very aggressively.

Bulbs are planted 3-4 inches apart and 2-4 inches deep in the fall. Sow in large numbers for maximum flowering impact under trees and shrub and in perennial beds. They should receive full day winter sunlight. All three companion bulbs are critter proof, not bothered by deer and voles. All are hardy in USDA hardiness zones 3–7. They often naturalize and the planting can last a lifetime.

All companion bulbs prefer compost-rich soil that is well-drained and moderately moist. Before planting pre-soak the bulbs overnight to hasten germination.

Snowdrops, winter aconites, and Glory of the snow are native to southern and eastern Europe.

Marcescence (Retaining Leaves Fall And Winter)

Posted by Hugh on October 31st, 2019

Through the fall and winter seasons, certain landscape and woodland trees retain their dead brown leaves on branches. Beech (Fagus spp.) and oak (Quercus spp.) are two common examples. Winter winds and precipitation will eventually force leaves to drop. Plant scientists term the retention of leaves as “marcescence”. There are many theories as to why this phenomena occurs.

Beech (*Fagus grandifolia*) hedge at NC Arboretum in Asheville, NC

True, most deciduous landscape trees shed their leaves in autumn. Cellular, physiological, and environmental changes are key factors. Growth regulator changes occur at the leaf abscission layer (the base of the leaf stalk or petiole. This process results in falling leaves. However, some hardwood trees retain their leaves throughout most of the winter season. For some gardeners, leaf retention is wonderful, but a few dislike having to rake leaves in the fall and again in early spring.

One is the first trees to evolve on planet Earth were evergreens such as (pines (Pinus), spruces (Picea), hemlocks (Tsuga), and firs (Abies). Other deciduous conifers such as bald cypress (Taxodium), dawn redwood (Metasequoia), and ginkgo (Ginkgo) soon followed. These trees encountered thousands of years of changing environmental and growing conditions. Next on the ecological chart were the broad-leafed hardwood trees which developed new ways of shedding their leaves. Short-lived trees like birch (Betula), maple (Acer), cherry (Prunus), and aspen (Populus) came next.

Beeches (Fagus) and oaks (Quercus) seemed to find a middle ground between evergreen and deciduous. Their leaves died, but did not drop in the fall. Evergreen and marcescent species increased their photosynthetic time and reduced nutrient losses by holding their leaves.

Young or newly planted trees often hold their leaves later into autumn. Once they become established in 1-3 years, leaf drop occurs at normal times, usually 3-4 weeks earlier. Marcescent foliage is also considered a deterrent to twig browsing by large four legged herbivores like deer and moose.

Lots Of Choices In European Hornbeams

Posted by Hugh on October 26th, 2019

European hornbeam

European hornbeam (Carpinus betulus),, aka ironwood and musclewood, is an underused tree in the U.S. It makes an excellent urban street and park tree. It develops a full, dense canopy and has very few maintenance requirements (USDA hardiness 4-7).

European hornbeams are planted across Europe for their formal upright form as street trees, privacy screens, and windbreaks. Seedling trees typically measure 40-60 feet high with a pyramidal to broad rounded canopy. Several cultivars are available, but some (like weeping and dwarf forms) may be difficult to purchase in U.S. nursery commerce.

Its dense summer foliage is medium green, leaves up to 4 inches in length, and exhibit little susceptibility to disease and insect problems. Flowers (catkins) are visible in early spring before the foliage emerges. Male catkins are yellowish and female catkins are greenish. Fruits are small nutlets in 3-lobed bracts that appear in late summer.

Hornbeams adapt to a wide range of soils and grow best in full sun. Trees tolerate hot and dry conditions once established in the landscape, but prosper in cool well mulched ground. Trees tolerate occasional wetness and slightly alkaline soil pH. Annual feeding of young trees with a slow-release fertilizer is highly recommended.

Dense, compact and narrow when young, they develop a wide oval crown with maturity. Long, thick, dark green foliage with prominent veining finish a pleasing yellow-orange in autumn. Trunks have smooth gray bark and distinctive muscular fluted bark.

Hornbeams are an excellent choice for hedging and windbreaks, particularly upright growing forms. Trees are mostly free of disease and pest issues. Powdery mildew may occur after a wet summer and Japanese beetles may sometimes chew on summer foliage. Little or no pruning is generally needed.

Found on the streets of U.S. cities are three upright branched European hornbeam cultivars: ‘Fastigiata’, ‘Columnaris’, and ‘Frans Fontaine’. Refer to other blogs for cultivar descriptions.

Black Gum (Tupelo) Tree

Posted by Hugh on October 21st, 2019

Black gum (Nyssa sylvatica) or tupelo tree is a native to Eastern North America (USDA hardiness zones 3-9). It is native from the New England states southward into Florida and west to Eastern Texas. Seedlings of this wonderful woodland and landscape tree start off slowly, but will mature to heights of 50 to 60 feet and 20 to 25 feet in width. Because of its tap-rooted nature, it is best to purchase nursery grown trees six inches or less. Allow 2-3 years for the tree(s) to established. Afterwards, black gum trees grow as rapidly as a sugar maple and make an ideal yard shade tree.

The 3-6 inch high gloss dark green summer foliage. Fall leaf color is expressed early, often in early September and continues through mid- to late- October, a blend of yellow, orange, purple, and red shades, rarely the same one year to the next. The light gray bark on a young tree becomes deeply furrowed with distinctive square ridges as the tree ages.

Black gum has a mostly dioecious flowering habit, which means that a tree produces either mostly male flowers while another tree bears mostly female flowers. The small spring flowers are prolific but are mostly inconspicuous. Blooms draw numerous nectar hungry bees. Tupelo honey is highly prized.

In some years female trees may be loaded with berries, while mostly male trees bear only a few berries. The bluish-black fruits (berries) attract numerous birds and many four-legged critters. Deer are not a problem.

Disease and insect issues are minimal if the tree is sited properly. Leaf spot problems are best avoided by selecting resistant varieties (cultivars). Recommended cultivars are ‘Wildfire’ and Green Gable®. Black gum’s fire risk rating is low.

Black gum is an excellent ornamental shade tree and a street tree. The tree grows well in moist soils including sites prone to periodic flooding. Formerly rated as difficult to transplant, modern day nursery practices permit more production of black gums.

Inkberry Holly Substitute For Boxwood

Posted by Hugh on October 16th, 2019

Ilex glabra ‘Densa’

Ilex glabra ‘Compacta’ – black fruits

Inkberry holly (Ilex glabra), also called gallberry, is a slow-growing broadleaf evergreen shrub (USDA hardiness zones 4-9). It grows to 5-8 feet tall and can spread by root suckers and form colonies. Inkberry is native from the eastern coast of Canada south to Florida, west to Louisiana. The shrub is at home in sandy woodlands and edges of swamps and bogs.

The small, dark green, glossy leaves (to 1.5 inches long) are smooth edged without any spines. Foliage stays attractive in winter unless temperatures dip below 0 °F. Greenish white flowers appear in spring, but are mostly inconspicuous. Jet black, berry-like drupes (3/8 inch diameter) mature in early fall and persist throughout late winter into early spring unless eaten by birds and other wildlife.

Inkberry hollies are popular hedging shrubs that look like boxwoods (Buxus spp.). Their growth rate is greater than boxwoods. This durable shrub grows in average, medium to wet, acidic soils and in full sun to partial shade. It is one of few holly species that tolerates wet soils.

Inkberries are dioecious, either male or female plants. Female plants need a male pollinator in order to produce the berry-like drupes that are characteristic of the species and cultivars. Prune in early spring before new growth begins. Plants generally need minimal pruning unless used as a hedge. Remove root suckers if undesired.

No serious insect or disease problems trouble inkberry hollies. Leaf spotting occurs in wet summers. Spider mites may appear, especially during dry weather.in high pH (alkaline) soils, foliar chlorosis (yellowing) may happen. Spider mites may appear, especially in hot dry weather.

Mass or group several inkberry hollies as a shrub border, a low foundation planting. Species inkberries will naturalize in moist woodland gardens or near streams or ponds. Fertilize in spring with an acidic water soluble fertilizer such as Holly-Tone® or Miracle-Gro®.

When shopping at local garden centers, ‘Densa’, ‘Nordic’, and ‘Shamrock’ are popular cultivars. Densa inkberry holly is a female clone, but any male holly should be able to pollinate the flowers. All exhibit dense branching, compact growth habit, and less root suckering compared to the species. Avoid varieties that become “bare-legged” or “raise their skirts”.

Honey derived from inkberry flowers is a highly-rated; it is locally marketed at some farm markets in the southeastern U.S. Dried and roasted inkberry leaves were first used by Native Americans to brew “Appalachian tea” a black tea-like drink.

25 Trees For Autumn Leaf Color

Posted by Hugh on October 11th, 2019

Fall leaf colors of woodland and landscape trees vary from one year to the next. Foliage colors are determined by monthly weather conditions and several environmental factors. Rainfall amounts and daily temperature levels during August and September are key determining factors.

Best autumn leaf colors develop as daytime hours are shortening, daytime hours are sunny and cool, and nights stay cool with temps above freezing (32°F). Wind and rainfall are also factors. Trees should be healthy and not troubled by disease and pest problems. While some dry weather is ok, extended dryness lasting 4-5 weeks may cause leaves to shrivel and fall prematurely.

Green leaves develop purple/red/orange/yellow in response to late summer/fall cool temperatures:

· Yellow and orange leaf colors become more noticeable as the carotenoid pigments emerge. Chlorophyll greens fade away and no longer mask the carotene hues.

· Red hues, caused by the leaf anthocyanins, develop in the cooler days. Phosphate exits the leaves, moving downward into the roots. More sunlight equals more anthocyanin and more intense red hues.

Finally, tree selection is important. Particular tree species and their cultivars are genetically superior with regard to autumnal leaf colors. A list of twenty –five (25) U.S. native and non-native tree species highly rated for their fall color follows. They are not posted in any specific order.

Red maple (Acer rubrum) – ‘Red Sunset’, October Glory’

Sugar maple (Acer saccharum) – ‘Green Mountain’

Japanese maples (Acer palmatum) – fall color are variable/ dependent on cultivar

Vine maple (Acer circinatum)

Amur maple (Acer ginnala) – ‘Flame’

Sweet gum (Liquidambar styraciflua)

Ginkgo, maidenhair tree (Ginkgo biloba)

Black gum, tupelo (Nyssa sylvatica) – ‘Wildfire’, Red Rage’, Green Gable®

Washington hawthorn (Crataegus phaenopyrum)

Serviceberry tree (3) – (Amelanchier x grandiflora); downy serviceberry (A. arborea); Allegheny serviceberry (A. laevis)

Red oak (Quercus rubra)

Flowering dogwood (Cornus florida)

Chinese or kousa dogwood (Cornus kousa)

Green ash (Fraxinus pensylvanicum)

Katsura tree (Cercidiphyllum japonicum)

Sassafras (Sassafras albidum)

Staghorn sumac (Rhus typhina)

Hickories (Carya spp.)

River birch (Betula nigra)

Gray birch (Betula populifolia)

Sweet birch (Betula lenta)

American persimmon (Diospyros virginiana)

Quaking aspen (Populus tremuloides)

Bald cypress (Taxodium distichum)

Franklin tree (Franklinia alatamaha)

Emerald Ash Borer Update

Posted by Hugh on October 6th, 2019

Foliage of Blue Ash (Fraxinus quadrangulata)

Emerald Ash borer (EAB) is confirmed to infest in many areas of the U.S. Emerald ash borer (Agrilus planipennis) is an exotic beetle that was discovered in southeastern Michigan near Detroit in 2002. EAB adult beetles nibble on ash foliage but cause little damage. The beetle larvae (immature stage) feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients.

EAB is native to Asia and probably arrived in the U.S. around 1990 in wood packing material. Over 100 millions of ash trees have been lost in over 18 states, and in Ontario and Quebec, Canada. The cost to municipalities, property owners, nursery operators and forest products industries is in the tens of millions of dollars in the treatment and tree removal costs or lost logging production. This pest continues to spread.

EAB threatens the entire North American Fraxinus genus, unlike past invasive tree pests, which have threatened only one or a few species within a genus. Green ash (F. pennsylvania), black ash (F. nigra) and white ash (F. americana) trees are preferred hosts. Blue ash (F.
quadrangulata) displays temporary resistance to the EAB larvae but are eventually killed as well.

EAB is a very destructive insect pest in North America in terms of both the number of trees affected and the economic losses associated with the treatment and removal costs.

According to University of Tennessee plant scientists, property owners should: 1. Don’t transport firewood, even within the state. 2. Use firewood only from local sources, or purchase firewood that is certified (labelled) to be free of pests. 3. If you have moved firewood, burn all of it before leaving your campsite. 4. Watch for signs of infestation in your ash trees.

Finally, if you suspect an ash tree to be infested with EAB, call your county or city Extension office or contact a state certified arborist.

EMERALD ASH BORER

Ultra Dwarf Korean Fir

Posted by Hugh on October 1st, 2019

Korean fir (Abies koreana) is slow-growing compact fir species with a mature height between 15 to 30 feet tall and 6 to 15 feet wide. Its tiny needles are ½- to 1- inch long, green on top and two white stripes on the underside. It bears 2-3 inches long erect purple cones almost annually that mature to tan color in fall. Unlike other conifers, the cones
stand upright on the top of branches.

Dwarf cultivars of Korean firs are favorites among many conifer collectors (USDA hardiness zones 5-8). These ultra-dwarf varieties grow inches per year. To encourage a deep extensive root system, extra care (TLC) is needed the first 2-3 years after planting in the garden.

Plant in a humus-rich, acidic, well-drained soil and in a sun to partial shade garden bed. Mulch with acidic organic compost such as pine needles, shredded pine bark, or chips. Irrigate once or twice monthly during periods of drought, heat or high winds.

‘Horstmann’s Silberlocke’ is the leading Korean fir variety among conifer collectors. The German word silberlocke means “silver locks of hair”. The needles on the branches curl on the tops exposing the white underside of the needles, resulting in a frosted look. Annual growth rate is 6 – 8 inches (15 – 20 cm). Over the years, ‘Horstmann’s Silberlocke’ will develop into a small 12 feet high x 8 feet wide landscape tree. The curling needle trait is often lost as the plant age. ‘Silberlocke’ also produces purple/tan cones on young plants.

‘Cis’ grows very slowly into a round (globose) compact bun with glossy dark green needles with silvery undersides. After 10 years of growth, a mature specimen will measure 16 inches (40 cm) tall and wide.

‘Silver Pearl’ (‘Silberperle’) is a slow-growing globe-shaped cultivar with green needles above and silvery needle on underside along with a slight twist. Its very conspicuous winter buds are described as small pearls, hence its name. Ultra-dwarf annual growth rate is only 2 to 3 inches (5 – 7.5 cm) resulting in a squat 2 feet (60 cm) tall and 18 inches (45 cm) wide conical tree after 10 years.

‘Kohout’s Icebreaker’ is a superb new introduction with curled needles revealing brilliant white reverse. (8-12 x 12-18 inches tall and wide after 10 years.

Korean fir appears to be more heat tolerant than other firs, but it prefers cooler regions of the U.S. As with most firs in the South, Korean fir will often fail if too hot and will fail in wet soppy soils. In the warm humid southeastern U.S. environment, Korean fir should be grafted on Momi fir (Abies firma) rootstock. Dwarf forms make great additions to a small urban garden, a rockery, or a large container. Korean fir is rated as deer resistant.

Because of their rates of growth, super dwarfs are investments in the future. A plant with some size will likely command a premium price.