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

For Dry Sites Try Arizona Cypress

Posted by Hugh on January 11th, 2014

Cupressus ‘Blue Pyramid’ on ETSU campus in Johnson City, TN

Arizona cypress (Cupressus glabra) is silvery blue needled medium-sized evergreen (USDA hardiness zones 6 to 9). This southwest U.S. native demands full sun and excels in droughty, infertile, and well-drained soils. Conversely, Arizona cypress does not tolerate shade, poor air circulation and flooded soil. Arizona cypress is mostly disease and pest free unless too crowded in a landscape.

‘Blue Ice’, ‘Blue Pyramid’, and ‘Carolina Sapphire’ are three leading cultivars. The latter cultivar exhibits a silvery needle fine foliage, but may be northern hardy to zone 7. Depending on the cultivar planted, this upright branched pyramidal conifer grows rapidly to 30-50 feet high and 15-20 feet wide. An older specimen displays a rugged or furrowed trunk with reddish brown bark, a showy contrast with the silvery to steel blue foliage.

Whether planted as a single specimen or with several grouped together as a privacy fence or windbreak, the metallic needle foliage offers different foliage color with other conifer species. While needle color of some conifers may turn bronze or brown in winter, the silvery blue needle color seems to intensify.

Fall thru early spring are ideal times to plant Arizona cypress. Planting on a slope is highly recommended to avoid soils from becoming too soggy. This evergreen is not finicky regarding soil fertility or pH. Arizona cypress exhibits excellent drought tolerance once established for two years. Pruning is rarely necessary except to remove a wayward or broken branch.

‘Carolina Sapphire’ (left) and Cryptomeria

Shagbark Hickory

Posted by Hugh on January 8th, 2014

Shagbark hickory

Most tree lovers don’t plant U.S native shagbark hickory (Carya ovata) (USDA hardiness zones 4-8). Instead, they often inherit one when purchasing property. Shagbark hickory is notoriously difficult to transplant and grows very slowly in its early years. Like oaks (Quercus spp.) and beeches (Fagus spp.), hickories are long-lived, often standing tall in an open woodland setting for 200 years or more. Success with growing hickory is to not disturb its roots.

Shagbark hickory is a large tree, reaching 60-80 feet in height, but is capable of growing over 100 feet. Hickory grows naturally in moist well-drained river bottom soils although it is not uncommon to find hickory growing in a dry upland site.

Summer foliage is medium green and coarse textured. Leaves are alternate, pinnately compound, 8-14 inches long with usually 5 leaflets, sometimes 7. Each leaflet is 4-6 inches long and 1 – 2 ½ inches wide. Leaves stay mostly blemish-free until minor leaf spot diseases arise in late summer. Hickory is susceptible to a number of environmental stresses, including drought and hickory bark beetles. Over a 3-4 week period leaves color from bright gold to bronze before abscising in late autumn.

Male and female catkin flowers appear on the same tree in mid-spring and get little notice. Hickory nuts are a delicious food resource for humans as well as woodland inhabitants, including several bird species. The thin shelled round nuts are 1 – 1 ½ inches in diameter. Among nut lovers trees with sweet kernels and quality are tagged.

The grayish brown bark separates into thin curved plates, creating an overall “shaggy” appearance, hence the name “Shagbark Hickory.” Over the years large amounts of bark, leaf and nut debris may accumulate lots of litter. Hickory’s beauty far outweighs a little extra raking.

Hickory is a large shade tree suited for large properties, parks and golf courses. Winter gray shaggy bark and golden fall color are its major assets.

Moving Large And Mature Trees

Posted by Hugh on January 5th, 2014

Mature ‘Crimson Queen’ Japanese maple at Samara Farms Nursery, Nashville, TN

Perhaps tree lovers can’t plant wonderful trees such as shagbark hickory (Carya ovata), American beech (Fagus grandifolia), or white oak (Quercus alba). They can purchase property with the tree(s) growing on them. Most nurseries do not grow these difficult species or guarantee their success after planting. But, all is not lost!

Modern nurseries, backed by university research, have debunked many tree planting myths. For example, the recommended size and shape of a planting hole has changed. Digging a wide shallow hole is better than a narrow deep one.

Perhaps an old 100 year old Japanese maple may require a new home. There are specialty nurseries which are able to transport old mature trees hundreds of miles. We know more about how trees grow and the best time to lift and transplant one to a new hole several hundred miles away.

Some difficult to transplant trees can be moved during a narrow window of 4 to 6 weeks commencing in mid-winter. Digging is performed by a knowledgeable certified arborist and a specialty nursery with the proper equipment. These tree experts are listed on the International Society of Arboriculture (ISA) website: www.treesaregood.org

Some tree species are reputed to being difficult to move. Blackgum or tupelo (Nyssa sylvatica) is one such tree. Perhaps, this was true 50 to 100 years ago, but better cultivars have come along. Cultivars ‘Wildfire’ and ‘Red Rage are improved blackgum selections.

Past Winners of the Perennial Plant of The Year Award

Posted by Hugh on January 1st, 2014

'Karl Foerster' Feather Reed Grass

Arkansas Blue Star

Each year PPA members choose a Perennial Plant of the Year™. Since 1990 24 great plants have been selected. Some of the selection criteria include:
• Suitable to a wide range of climatic conditions
• Low Maintenance
• Pest and disease resistant
• Availability at garden centers
• Multiple seasons of color (beauty)

The list of Perennial Plant of the Year winners:
1990 Creeping phlox (Phlox stolonifera)
1991 Palace Purple coralbells (Heuchera micrantha ‘Palace Purple’)
1992 Moonbeam coreopsis (Coreopsis verticillata ‘Moonbeam’)
1993 Sunny Border Blue veronica (Veronica ‘Sunny Border Blue’)
1994 Sprite astilbe (Astilbe ‘Sprite’)
1995 Russian sage (Perovskia atriplicifolia)
1996 Husker Red penstemon (Penstemon digitalis ‘Husker Red’)
1997 May Night salvia (Salvia ‘May Night’ (‘Mainacht’))
1998 Magnus purple coneflower (Echinacea purpurea ‘Magnus’
1999 Goldsturm blackeyed Susan (Rudbeckia fulgida var. sullivantii ‘Goldsturm’)
2000 Butterfly Blue scabiosa (Scabiosa columbaria ‘Butterfly Blue’)
2001 Karl Foerster feather reed grass ( Calamagrostis x acutiflora ‘Karl Foerster’)
2002 David summer phlox (Phlox ‘David’)
2003 Shasta daisy (Leucanthemum ‘Becky’)
2004 Japanese painted fern (Athyrium niponicum ‘Pictum’)
2005 Lenten rose (Helleborus x hybridus)
2006 Firewitch dianthus (Dianthus gratianoplitanus ‘Feuerhexe’)
2007 Walker’s Low catmint (Nepeta ‘Walker’s Low’)
2008 Rozanne cranesbill (Geranium ‘Rozanne’)
2009 Aureola Japanese forest grass (Hakonechloa macra ‘Aureola’)
2010 Wild indigo (Baptisia australis)
2011 Arkansas bluestar (Amsonia hubrichtii)
2012 Jack Frost brunnera (Brunnera macrophylla ‘Jack Frost’)
2013 Variegated Solomon Seal (Polygonatum odoratum ‘Variegatum’)

For a complete description of each plant, log onto the Perennial Plant Association Website.

2014 Perennial Plant Of the Year: ‘Northwind’ Switchgrass

Posted by Hugh on December 29th, 2013

‘Northwind’ Panicum In 1/2 Day Sun

Late October fall color in East Tennessee

Northwind switchgrass (Panicum virgatum ‘Northwind’) is a 4 to 5 feet tall native prairie grass (USDA hardiness zones 4–9). There are many fine switchgrass varieties, but its Northwind’s vertical form and steel blue foliage that makes it a standout. Northwind switchgrass has been selected the 2014 Perennial Plant of the Year.

By mid-summer its lacy soft pinkish white inflorescences arise 1-2 feet above the foliage. In early autumn floral heads take on more of a grayish tint. The narrow grass blades also turn several shades of yellow. Its rigid form stands tall like a sentinel in the winter landscape and offer shelter to birds and other wildlife.

Switchgrass grows the best in full sunlight. Its tight upright form lets down in partial shade. Switchgrass prefers moist fertile soil, but adapts to most soil types and moisture levels. Nutritional needs are minimal, and switchgrass forages well in nutrient poor soils.

This tough prairie inhabitant sloughs off winter’s cold and summer’s heat and drought. Disease or pest problems are minimal, but may contract outbreaks of rust over a wet summer. Overcrowded crowns are best divided every 4-5 years, no easy task.

Northwind’s neat vertical stance and steel blue blade color make it ornamental pleasing in residential, roadside, and commercial properties. Northwind may stand alone or mixed with other plants in containers. It can be massed along a stream bank, or set on steep slopes or reclamation lands. Plant switchgrass for dune stabilization along coastal beaches; it tolerates high winds and salt sprays.

Leyland Cypress – Alternative Christmas Tree For The South

Posted by Hugh on December 25th, 2013

x Cupressocyparis leylandii

If you grew up with a spruce or a fir Christmas tree, Leyland Cypress (x Cupressocyparis leylandii) could be a big change. This conifer species thrives in the southern U.S. (USDA hardiness zones 7-b to 9). Leyland is a good choice for a live cut or transplanted holiday tree as firs (Abies spp.) and spruces (Picea spp.) fail in the southern U.S. heat and humidity. It also grows well in a landscape container.

The scale-like foliage holds its natural green color much better and does not shed compared to the popular Fraser or balsam firs. If it does not, the tree is likely bone dry and a potential fire hazard.

Don’t purchase a leyland that has been cut more than two weeks and laying in a tree sale lot. It is better to visit a Choose and Cut grower. A fresh cut leyland from a tree lot generally does not need to be re-cut when setting the butt into the stand. Leyland can hold heavy ornaments if it has been properly sheared at the tree farm.

Once set up in the home, keep the cut tree away from heating vents and water as needed. Similarly, a live balled and burlapped (b&b) or container tree should be treated the same. Inside a warm home too long, it may break dormancy and be susceptible to the frigid winter weather when transplanted outdoors. Limit its time inside the home to two weeks.

Leyland continues to increase in popularity as a Southern Christmas tree. It is ready to sell as a Christmas tree in 4 to 5 years compare to 7 to 8 years for firs, pines and spruces.

Credit: Dr. Ken Tilt, retired professor of Horticulture from Auburn University, provided much of the information written here.

‘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.