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

‘Ogon’ Dawn Redwood Offers 4-Seasons Interest

Posted by Hugh on December 9th, 2013

Summer Foliage of 'Ogon' Metasequoia

Dawn redwood (Metasequoia glyptostroboides ‘Ogon’ (aka ‘Gold Rush’) is a stunning foliage color variant (USDA hardiness zones 5 to 8). Metasequoia was thought to be extinct until the mid-1940’s when rediscovered in China. Its leaves were commonly found imprinted in fossil rocks.

When developing your landscape plan, place Ogon where it will become a focal point on the property. New foliage emerges clear yellow in the spring and turns a steadfast chartreuse color through in spring and summer months. In the fall the soft feathery leaves finish burnt orange and blanket the ground surface. After several years thin peeling strips of mahogany-colored winter bark and vertical silhouette make Ogon a four-season delight.

Dawn redwood prefers a moist well-drained soil and is tolerant of wet sites for short intervals lasting a few weeks. Full sun and adequate soil moisture are necessary to retain foliage color longest. Dawn redwood exhibits no serious disease or pest problems. New foliage may scorch, often indicating need for additional watering when tree(s) are young.

An Ogon tree grows one-third less than the species @ 50 to 60 feet high and 30 feet wide. Utilize as a specimen or park tree on medium to large properties. Align several together in an allee΄ design such as seen at Juniper Level Botanical Garden at Plants Delight Nursery in Raleigh, NC.

Japanese Umbrella Pine Is Unique Among Evergreens

Posted by Hugh on December 6th, 2013

Umbrella pine at North Carolina Arboretum in Asheville

Sciadopitys verticillata

Umbrella pine (Sciadopitys verticillata) is an outstanding evergreen large shrub or medium-sized pyramidal tree. Initially, umbrella pine grows slowly, only 6 to 8 inches annually, but growth rate picks up after 4-5 years. A young 3-foot tall plant may reach 20 to 30 feet tall in 25 years and double that at maturity.

Its leaves are unique–dark green, 2 to 5 inches long, flat glossy needles. Leaves are thick and wide, and rarely turn off-color in Southern Appalachian winters (USDA hardiness zones 6 and 7). Clusters of 20 to 30 long flat needles are arranged like the spokes of a wheel or an umbrella. Needles are retained 3 or more years; the old needles shed and neatly pile up on the ground as mulch.

Umbrella pine prefers one-half to full day sun planted in compost-rich, moist, well-drained, acidic soil. Provide moderate afternoon shade against summer heat in zone 7. Umbrella pine is a fossil tree and has survived through geologic time to ward off disease or insect pests. Pruning is rarely a chore, perhaps to remove multiple leaders or a small dead twig.

No two umbrella pines look alike and their growth rates are quite variable. Trees reach cone-bearing age in approximately 20 years. The 1-inch long flowers and 2-4 inch green cones are of little ornamental value. The shaggy reddish brown bark on a 25 year and older tree exfoliates in long narrow strips.

Umbrella pine is not commonly sold garden centers and are expensive. ‘Aurea’ (gold needle), ‘Mitsch Select’ (dwarf), and ‘Pendula’ (weeping) forms are available from select e-commerce nurseries. Locate an umbrella pine where you achieve the best visual impact such as adjacent to a patio or deck.

Not a true pine (Pinus spp.), umbrella pine is closely akin to yew (Taxus spp.). Its long flat needled leaves are found embedded in fossil rocks from prehistoric Europe, Canada and Greenland.

Landscape Shrubs Rarely Damaged By Deer

Posted by Hugh on December 1st, 2013

Cryptomeria 'Elegans Nana'

Deer Resistant 'Vanhouette' Spirea

Deer will eat or nibble on any landscape plant, particularly when they’re starving. Abnormally high deer populations, starved by a shortage of their favorite foods (mast), will feed or browse on almost any plant. This is a survival reaction. To truly protect plants when deer numbers are unusually high, a tall fence or reinforced netting may be your best options. Other preventatives include installing electrified fencing and spraying with commercially available repellents.

Deer do not read plant lists that they’re should not eat. The list below includes landscape shrubs that deer seem to bother less than most. The list is a compilation from wildlife experts in the eastern U.S. It does not include every landscape shrub reported and some potentially invasive species have been edited out.

Deer species and numbers vary across this big country. A deer’s food palate may differ from one region to another. It also depends on how hungry the deer in an area may be. Obviously, you should not be inviting deer by planting shrubs that are their dining favorites, such as yews (Taxus spp.), arborvitae (Thuja spp.), hemlock (Tsuga spp.), rhododendron, azalea, burning bush (Euonymus alata), and several others.

Some native shrubs such as bottlebrush buckeye, chokeberry, shrub dogwoods, elderberry, and brambles are important food sources for deer and other wildlife. Often, deer do little significant damage to the host plant(s) or they recover quickly. If you are planting young host shrubs into a landscape, you should fence them off for 3-5 years until they’re large enough and well established.

Deer Resistant Shrubs

Glossy Abelia (Abelia spp.)
Bottlebrush Buckeye (Aesculus parviflora)
Devil’s Walking Stick (Aralia spinosa)
Red Chokeberry (Aronia arbutifolia)
Goldust Plant (Aucuba japonica)
Barberry (Berberis spp.)
Butterfly Bush (Buddleia spp.)
Boxwood (Buxus spp.)
Beautyberry (Calicarpa spp.)
Heather (Calluna spp.)
All-spice Sweetshrub (Calycanthus floridus)
Blue Mist Shrub (Caryopteris clandonensis)
Plum Yew (Cephalotaxus harringtonia)
Japanese Flowering Quince (Chaenomeles japonica)
Flowering Quince (Chaenomeles speciosa)
Falsecypress (Chamaecyparis pisifera)
Fringetree (Chionanthus viriginicus)
Sweet Pepperbush (Clethra spp.)
Red Twig Dogwood (Cornus alba)
Red Osier Dogwood (Cornus sericea)
Hazelnut (Corylus spp.)
Smokebush (Cotinus coggygria)
Many Cotoneaster (Cotoneaster spp.)
Japanese Cedar (Cryptomeria japonica) -shrub forms
Daphne (Daphne spp.)
Deutzia (Deutzia spp.)
Redvein Enkianthus (Enkianthus campanulatus)
Heath (Erica spp.)
Forsythia (Forsythia x intermedia)
Fothergilla (Fothergilla spp.)
Common Witchhazel (Hamamelis virginiana)
Rose of Sharon (Hibiscus syriacus)
St. John’s Wort (Hypericum prolificum)
Most hollies (Ilex spp.) -those with spiny leaves
Virginia Sweetspire (Itea virginica)
Most Juniper species (Juniperus spp.)
Crape Myrtle (Lagerstroemia indica)
Common Privet (Ligustrum spp.)
Spicebush (Lindera benzoin)
Coast Leucothoe (Leucothoe axillaris)
Drooping Leucothoe (Leucothoe fontanesiana)
Japanese Kerria (Kerria japonica)
Beautybush (Kolkwitzia amabilis)
Saucer Magnolia (Magnolia x soulangiana)
Oregon Grape Holly (Mahonia aquifolium)
Leatherleaf Mahonia (Mahonia bealei)
Russian Arborvitae (Microbiota decussata)
Northern Bayberry (Myrica pensylvanica)
Holly Osmanthus (Osmanthus heterophyllus)
Sweet Mock Orange (Philadelphus coronarius)
Japanese Pieris, Andromeda (Pieris japonica)
Mugo Pine (Pinus mugo)
Bush Cinquefoil (Potentilla fruticosa)
Cherry Laurel (Prunus laurocerasus)
Firethorn (Pyracantha coccinea)
Buckthorn (Rhammus spp.)
Fragrant Sumac (Rhus aromatica)
Currants (Ribes spp.)
Brambles (Rubus spp.)
Elderberry (Sambucus canadensis)
Sweet Box (Sarcoccoca hookeriana)
Japanese Spirea (Spiraea japonica)
Bridalwreath Spirea (Spiraea prunifolia)
Anthony Waterer Spirea (Spiraea x bumalda)
Snowberry (Symphoricarpos albus)
Coralberry (Symphoricarpos x chenaultii)
Japanese Tree Lilac (Syringa reticulata)
Common Lilac (Syringa vulgaris)
Bald Cypress (Taxodium distichum) -shrub forms
Koreanspice Viburnum (Viburnum carlesii)
Arrowwood Viburnum (Viburnum dentatum)
Cranberry Viburnum (Viburnum opulus)
Doublefile Viburnum (Viburnum plicatum tomentosum)
Blackhaw Viburnum (Viburnum prunifolium)
Leatherleaf Viburnum (Viburnum rhytidophyllum)
Judd Viburnum (Viburnum x juddii)
Weigela (Weigela florida)

Top Conifers Picks By Southeast Reference Gardens

Posted by Hugh on November 28th, 2013

Favorite Platycladus orientalis 'Morgan' at UT Gardens, Knoxville, TN

Favorite Umbrella Pine at NC Arb. in Asheville, NC

In 2011 poll conducted at the SE Region meeting in Athens, GA, the top favorite conifer picks from SE Reference Gardens.

Georgia
Lockerly Arboretum, Milledgeville
Cryptomeria japonica ‘Elegans Nana’
Juniperus virginiana var. silicicola ‘Brodie’
Platycladus orientalis ‘Aurea Nana’
Thuja occidentalis ‘Rheingold’
Smith Gilbert Garden, Kennesaw
Cedrus deodara ‘Gold Cone’
Chamaecyparis obtusa ‘Verdon’
Platycladus orientalis ‘Morgan’
State Botanical Garden, Athens, GA
Juniperus virginiana ‘Grey Owl’
Pinus virginiana ‘Wate’s Golden’
Platycladus orientalis ‘Morgan’

North Carolina
J.C.Raulston Arboretum, Raleigh
Momi fir (Abies firma)
Calocedrus macrolepis var. formosana
Cryptomeria japonica ‘Rein’s Dense Jade’
Pinus wallichiana ‘Zebrina’
Podocarpus macrophyllus ‘Royal Flush’
Taxodium distichum var. imbricatum ‘Prairie Sentinel’

South Carolina
S.C. Botanical Garden, Clemson
Platycladus orientalis ‘Filiformis Pendula’
Sequoia sempervirens
Tsuga diversifolia

Tennessee
East TN State University Arboretum, Johnson City
Pseudolarix kaempferi
Sciadopitys verticillata
Thujopsis dolobrata
University of TN Gardens, Jackson
Cryptomeria japonica ‘Globosa Nana’
Platycladus orientalis ‘Franky Boy’
Thuja orientalis ‘Morgan’
University of TN Gardens, Knoxville
Chamaecyparis nootkatensis ‘Glauca Pendula’
Chamaecyparis obtusa ‘Spirited’
Juniperus deppeana ‘McFetter’s Blue’
Pinus densiflora ‘Aurea’
Platycladus orientalis ‘Franky Boy’

Virginia
Al Gardner Memorial Conifer Garden at J.Sargeant Reynolds Comm.College, Goochland
Cham. obtusa ‘Loughead’
Pinus parviflora ‘Tanima-no-yuki’
State Arboretum of Virginia, Boyce
Cupressus arizonica
Pinus pungens
Sciadopitys verticillata

Some of the conifers listed above turned up in several descriptions:
Japanese Umbrella Pine – Sciadopitys verticillata (zones 5 – 8a)
Platycladus orientalis ‘Franky Boy’ (zones 6 to 8a)
Thuja orientalis ‘Morgan’ (zones 6 to 8a)

Source: American Conifer Society, Southeastern Region, August 2013 Newsletter

Ranking Four Popular Evergreens As Privacy Screens

Posted by Hugh on November 25th, 2013

Emerald® Eastern Arborvitae

If you are searching for a tall evergreen conifer as a privacy screen, the four most popular in the Southern Appalachian region (USDA hardiness zones 6 and 7) are:

# 1 is Leyland cypress (x Cupressocyparis leylandii) which rapidly grows 40-50 feet tall and 20-25 feet wide in less than 25 years…if they live long enough. Leylands are mostly care-free the initial 10-12 years before an annual threat of fungus diseases arrives. They often grow too tall and wide in their space. Set leylands no closer than 18 feet apart at planting and require irrigation the first two summers if dry. There is little remedy for these diseases other than pruning on tall ladders.

# 2 is Japanese Cedar (Cryptomeria japonica), another fast grower, 30-40 feet tall and 20-25 feet wide after 30 years. Foliage tends to turn bronze colored over a cold winter (zone 6 and further north), but dark green needle color returns at the start of spring.

# 3 is ‘Green Giant’ arborvitae is a hybrid cross of (T. plicata), the west coast native arborvitae and Japanese arborvitae (T. standishi). Expect 25-30 feet height after 25 years. Species generally remains disease-free and rarely infested with bagworms. Native (non-hybrid) western arborvitae grows tall (50 feet) and narrow (15-20 feet) at maturity.

# 4 is Emerald® Eastern arborvitae (Thuja occidentalis), also called “Emerald Green”. It is semi-dwarf (slow grower), dark green compact shrub with narrow pyramidal form. Glossy bright green, flat sprays of scale-like needle foliage. This native arborvitae matures to 10 to 15 feet height and 4 to 5 feet width in 20-25 years.

All four conifers are hardy in zone 6. Eastern arborvitae is very hardy (zone 3), but not heat tolerant in the south (zone 8).

Mexican Feather Grass

Posted by Hugh on November 21st, 2013

Mexican Feather Grass In University of Tennessee Gardens, Knoxville in December

The ultra-fine soft foliage of Mexican feather grass (Nassella tenuissima) will grab your interest. Just a slight breeze will create wave movement in your garden (USDA hardiness zones 7 to 10). It grows 1½ feet high (2 feet tall in flower) and 1½ to 2 feet in width.

Mexican Feather Grass is a cool season grass native to dry rocky slopes and open grasslands from south central U.S. to Argentina. Established feather grass is highly drought tolerant. It thrives in full sun and average is well-drained soil. It grows poorly in either water-logged ground and in moderate shade.

Spring’s fine-textured foliage is lime-green followed by silvery-gold inflorescences in late spring. Summer’s heat and humidity causes this cool-season species to go dormant. Inflorescences age to a wheat-straw or blonde color. As temperatures cool down in the fall, Mexican feather grass goes through a second growth flush.

In the winter the foliage turns straw-colored, and plant form, texture and flowing habit all remain attractive. Cut back Mexican Feather Grass in late winter before spring’s growth flush begins. Mexican feather grass may re-seed, but is not difficult to manage.

Mexican feather grass performs well in rock gardens and xeric landscapes. It thrives planted in containers if not allowed to dry out. Its wispy threadlike foliage is attractive spilling over walls, boulders, or the edge of a container. Over time this vigorous grass tends to overwhelm most other perennials and annuals in mixed garden beds or containers.

Pyramidal Forms Of Cryptomeria

Posted by Hugh on November 19th, 2013

Japanese Cedar (Cryptomeria)

Needle foliage of cryptomeria

Cryptomeria, aka Japanese cedar, (Cryptomeria japonica) is an evergreen conifer native to China and Japan. It rated to be very long-lived (USDA hardiness zones 6 to 10). Some cultivars may be hardy in 5-b as well.

There are many forms of cryptomerias, ranging from dwarf globe-shaped shrubs to narrow pyramidal trees. Needle foliage may be green or golden sometimes contorted. Heights vary from 6 to 80 feet in height and 3 to 20 feet in width. All thrive in open full sun and good air circulation; they prefer an average moist well-drained acidic to neutral pH soil.

Pyramidal forms develop into beautiful evergreen privacy screens or hedges. Two to three year old established cryptomerias are superior to Leyland Cypress (x Cupressocyparis leylandii) in blizzard-proned and high wind areas. Young plants should be trained to a single leader. Cryptomerias suffer from few disease and pest problems. Prune off any discolored foliage as fungal blights cause inner foliage browning.

Five most popular pyramidal forms:
‘Yoshino’ is far and away the most popular cultivar, with a rapid growth rate (40 to 50 feet tall, 1/2 that in width) and bright green summer foliage; in zone 7 and areas north, typically foliage takes on a bronze winter tinge.

‘Ben Franklin’ grows slightly slower, more compact and darker green foliage than Yoshino. Similar height and width as Yoshino.

‘Radicans’ exhibits an upright, pyramidal form to 20 to 30 feet tall and 7 to 10 ft. wide in 12-15 years; popular choice in zone 7 gardens for its dark green non-bronzing foliage.

‘Black Dragon’ is 10 by 10 feet slow grower with dark green foliage.

‘Gyokuryu’ is “the Yoshino for small gardens” with a dense pyramidal form and dark green non-bronzing foliage; grows 5 to 6 feet in 10 years (10 to 15 feet in maybe 20 years).

Renewal Pruning Is An Easy Technique To Learn

Posted by Hugh on November 16th, 2013

Healthy Rhododendron Is Easy To Coppice

Renewal pruning is the practice of severely cutting back selected shrubs and trees. The task is simple. There are no books to read. Select a day from mid-February to early April (USDA hardiness zones 5-7). Cutback the entire shrub(s), leaving 3-5 inch tall cut stems or stubble. The cut stems will bud out in the spring along with adventitious buds below the soil line.

Renewal pruning can eliminate weather-damaged, diseased, and insect-riddled wood, particularly scale insects, without resorting to heavy pesticide use. All diseased and pest-ridden prunings should be removed from the property or burned. Healthy pruning wood can be ground up for mulch that is spread after 6 months or more composting.

Renewal pruning invigorates old shrubs, brightens foliage color, and increases fruit size and quality. Pruning tools needed: hand clippers, loppers, hand pruning saw, or chain saw. Do not use string trimmers (“weed-eaters”).

Renewal pruning may not the ideal practice for all shrubs.
• Summer flowering shrubs often recover and bloom the same year. Some spring flowering shrubs may not re-bloom for 1-2 years.
• Overgrown rhododendrons, hollies, pieris and mountain laurels respond better to a practice called “coppicing” in late September or early October in USDA hardiness zones 5-7.
• Plant health must be good. Weak, sickly shrubs may likely die when drastically cutback.
• Shrubs must be well-established for 3 to 4 years before renewal cutback.
• Don’t cutback grafted or budded plants in fear of losing the cultivar (above-ground portion) The root system may gain dominance.

Partial list of shrubs which respond to renewal pruning:

Glossy abelia (Abelia x grandifolia)
Butterfly bush (Buddleia davidii)
Beautyberry (Callicarpa spp.)
Blue mist shrub (Caryopteris x clandonensis)
Smoke tree (Cotinus coggygria)
Forsythia (Forsythia spp.)
Fothergilla (Fothergilla spp.)
Rose of Sharon (Hibiscus syriacus)
Smooth hydrangea (Hydrangea arborescens)
Pee Gee hydrangea (Hydrangea paniculata ‘Grandifolia’)
Oakleaf hydrangea (Hydrangea quercifolia)
Crape myrtle (Lagerstroemia indica x L. faurei)
Trumpet honeysuckle (Lonicera sempervirens)
Firethorn (Pyracantha spp.)
Sumac (Rhus spp.)
Rugosa rose (Rosa rugosa)
Pussy willow (Salix spp.)
Corkscrew willow (Salix matsudana)
Elderberry (Sambucus canadensis)
‘Hancock’ coralberry (Symphoricarpus orbiculatus ‘Hancock’)
Chaste tree (Vitex agnus-castus)
Weigela (Weigela florida)

Staghorn Sumac’s Reliable Fall-Winter Assets

Posted by Hugh on November 12th, 2013

Sumac Growing Along Roadside in Tennessee

Staghorn sumac (Rhus typhina) is known by several names, including velvet sumac and hairy sumac. This large shrub or small tree is native to northeastern U.S. and eastern Canada (USDA hardiness zones 3-8). Staghorn sumac often arrives uninvited into a landscape and its aggressive suckering root system makes it difficult to eradicate. For landscape use it should be limited to large properties with space for it to spread naturally.

Staghorn sumacs are noted their greenish yellow flowers in early summer and persistent red fruit clusters (drupes) in the fall and winter months. Its excellent scarlet red fall foliage color rarely disappoints. Plant in full sun for best color, but will cope in any light. Bright green pinnate leaves and reddish-brown fuzzy stems make sumacs easy to id along any road at high speeds. Male and female flowers occur on separate plants (dioecious).

Staghorn sumac grows 15 to 25 feet high and 15-20 feet wide. A pinnately compound leaf may be up to 24 inches long, comprised of 13 to 27 long narrow leaflets. Leaflets are bright green with serrated margins and glossy underside. The deep red hairy drupe fruits attract many kinds of winter feeding birds and other wildlife.

In winter young leafless stems appear club-like, covered with a dusty pubescence. As branches and trunks age, they shed their pubescence and become smooth and shiny. Prominent C-shaped leaf scars are characteristic over the winter branches, each containing an orange bud in the middle.

Rabbits and deer leave sumacs alone. Established plants are heat and drought and prosper in air-polluted urban environments and shallow rocky soil. Untended plants colonize to form a thicket from underground root suckers and seed dispersal. Roots mat in for erosion control. Disease and pest problems rarely happen when planted in open areas.

China Fir Deserves A Look

Posted by Hugh on November 9th, 2013

China Fir at Knoxville Botanical Gardens in TN

To begin, China fir (Cunninghamia lanceolata) is not a true fir (genus: Abies). Branches are broadly pyramidal when young, and open up to become slightly pendulous as the tree ages. China fir grows broad at the base and spire-like on top. The tree often grows multi-stemmed to 75 feet in height and 20 to 30 feet in width (USDA hardiness zones 6b-9).

Both male and female flowers of China fir form on the tips of branches. Clusters of several tiny male flowers and individual greenish-yellow female flowers open in May. The 1 ½ inch diameter brown round cones mature on the end of twigs. As the tree ages the brown bark exfoliates in strips to reveal a reddish-brown inner bark.

China fir grows best in moist, acidic, well-drained soil. Plant in full sun, but China fir will tolerate partial shade (minimum 6-hours sunlight). China fir performs best when cozied up among other trees to afford it summery shade and protection from wintry winds. Lower branches tend to lose out as tree ages. Following a severe winter some branches may dieback and should be pruned out. Otherwise, this conifer has few disease and pest issues.

Its long 2 ½- to 3-inch green to blue-green shiny needles offer a lush look. The sharp-pointed needles are spirally arranged and slightly twisted at the base. The winter foliage takes on bronze color during the winter in the Southern Appalachian region (USDA hardiness zones 6 and 7).

Several blue needle forms are now available, most from seedling sources and designated ‘Glauca’. Hardier forms have been rated to –10 to -15° F. Its light-colored soft fragrant wood is treasured in China.