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

‘Summer Cascade’ Is A Very Different Weeping River Birch

Posted by Hugh on December 22nd, 2013

Betula nigra 'Summer Cascade' At NC Arboretum in Asheville

Summer Cascade is a new weeping river birch (Betula nigra Summer Cascade™ (PPAF). Its pendulous branching habit represents a unique change for river birch. Its strong weeping nature creates a divine focal point planted next to a pond, deck, or patio.

Left unstaked, Summer Cascade’s strong pendulous habit naturally grows into a shrub mound or you can train it into a small to medium sized tree comprised of multiple layers of arching branches. New spring shoot growth is very flexible and can be easily twisted into many topiary forms.

Growth rate is very rapid. A 6 to 8 foot tall branched tree can be developed in one growing season from a rooted cutting. A 6-foot tree form, if left untended, may remain 6 feet tall, but broaden to 10-12 feet (width) over 10 years.

Calculating the eventual mature height and width of a Summer Cascade tree can be the job of a nurseryman or landscaper. To become a tree, it must be staked tall and trained in order to develop into a mature 35-50 foot majestic weeping river birch many years from now.

Summer Cascade is widely adapted to almost any site, including tolerances to high temperatures and wet soils. It grows best in an acidic soil (pH range of 5.0 – 6.2) with moderate soil fertility and ample soil moisture. Fall color may range from yellow to bronze. River birch’s showy bark is shaggy and dark tan in color. It is resistant to bronze birch borer and birch leaf miner.

Summer Cascade was introduced by John and Daniel Allen at Shiloh Nursery in Harmony, N.C.

‘Grey Owl’ Juniper Is Tough Carefree Evergreen

Posted by Hugh on December 18th, 2013

Old Planting Of ‘Grey Owl’ Juniper At Johnson City, TN Mall

Some people rate junipers as over-planted or bygone landscape plants. Juniperus virginiana ‘Grey Owl’ is a cultivar of our native Eastern Red Cedar (USDA hardiness zones 3 to 9). Eastern red cedar is actually a juniper. This flat spreading evergreen develops into a reliable ground cover not plagued with disease and pest problems observed on some other juniper species.

Grey Owl grows under open full sun in a variety of soils with adequate drainage. It grows 2 – 3 feet high and 4 – 6 feet wide. Two-year established plants are cold, heat, and drought tolerant. Eastern red cedars are resilient of windy sites and urban air pollutants.

New transplants start out slowly, but eventually toughen up and grow robustly. Their mature spread may not make them your first choice for planting in a small garden.

The most striking feature of Grey Owl is its silvery-gray foliage which shines all year long. In the winter landscape its silvery scaly foliage becomes tinged with purple, but its verdant color returns by the first day of spring.

In the Southeast U.S., Grey Owl is often seen planted as a roadside hedge along medians where little maintenance is provided. In some years shrubs may be infested by bagworms. Deer rarely trouble red cedars.

‘Holbert’ is another blue needle form wit feathery limbs are larger and low spreading plant to 2-3 feet tall and 8-10 feet wide. Low-spreading, bluish-green needles, and long extended shoots almost parallel to ground; Good blue foliage color holds well through the winter. ‘Holbert’ is a male cultivar of ‘Grey Owl’ and produces no cones.

Female plants produce loads of blue waxy berries or cones which attract loads of hungry birds over the winter.

Norfolk Island Pine Makes Decorative Holiday Tree

Posted by Hugh on December 15th, 2013

Norfolk Island Pine Growing Outdoors in St. Augustine, FL

Norfolk Island Pine (Araucaria heterophylla) is native to tiny Norfolk Island located in the South Pacific. This tropical evergreen tree is now planted around the world and appears to be hardy in Northern Florida (USDA hardiness zone 9). In the wild this fast-growing tree grows to 80 feet in height. Norfolk Island Pine makes a great house plant where it may range from 2 to 10 feet high.

Optimum room temperature should be around 65 -75° F and avoid cold air drafts and wild shifts in temperatures. It thrives in bright light but not in direct afternoon sunlight. An east or south facing window in your home is ideal. Rotate the plant at least twice monthly so that your tree stands tall and straight. Mist daily to increase the winter room humidity.

Water the plant weekly in spring summer and fall, but reduce watering frequency from December thru mid-March. Every 3-4 years repot into a larger sized container and fill with new potting media. Disturb the roots as little as possible. Fall seems to be the proper time to replant.

Feed monthly in spring and summer with half strength of a water-soluble fertilizer such as Schultz™, Miracle-Gro™, Daniels™, or equivalent.

Container size controls the ultimate height and spread of your Norfolk Island Pine. Larger pot equals larger plant. Prune off all dead or yellowed twigs and branches at any time. The short light green needles are shed after 2 to 3 years. New outer growth generally covers over most needle lost.

Once threats of spring frost have subsided, Norfolk Island Pine can be moved outdoors under a shade tree and cared for. You may decorate it as a living Christmas tree. Remove all ornaments once the holidays are over.

When To Prune Off Old Foliage Of Evergreen Perennials

Posted by Hugh on December 12th, 2013

Fresh New Spring Foliage And Flowers of Epimedium

Foliage of many popular evergreen perennials often appear tattered after a long cold winter. Coralbells (Heuchera spp.), foam flowers (Tiarella spp.), monkeygrass (Liriope spp.), fairy wings (Epimedium spp.), creeping phlox (Phlox subulata), periwinkle (Vinca minor), Japanese spurge (Pachysandra terminalis), and Christmas fern (Polystichum acrostichoides) are stunning evergreen groundcovers.

The solution is simple– just prune them. In late winter tidy up evergreen perennials before new growth or flowers appear. New growth on coralbells appears at the plant center. If spring growth has already started, do not trim off the new foliage as it may retard plant growth. Feed perennials with granular 10-10-10 or equivalent fertilizer and they’re ready for a new growing season.

Many low spreading ground cover perennials, such as fairy wings, perwinkle, Japanese spurge, and Christmas ferns, can be mowed down before new spring growth and flowers arise. Set the mower height at 4-5 inches tall, in “mulching mode”, and slowly grind though the bed, and leave the debris for long term improvement of the soil.

Prune off oldest low (basal) foliage of Christmas rose (H. niger) and Lenten rose (Helleborus x hybridus) in late autumn as new growth emerges or wait for winter flowering has begun. Christmas rose blooms around the winter holidays while Lenten roses flower in February and March. Removal of old foliage gives plants a fresh bouquet appearance.

Add the clippings to the compost bin unless the plant debris is heavily disease infected.

New Growth Starting On Lenten Roses By Early December

‘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.