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

“Death By Mower” Disease

Posted by Hugh on January 22nd, 2014

Dead Dogwood By “Mower Disease”

“Mower disease” is a totally preventable human malady caused by permitting lawn grasses and weeds from growing near the crown of trees and shrubs. The problem is commonly seen on large properties such as church grounds, cemeteries and public parks. Large gang mowing machines (with many reels) cut 95-98% of the turf area. Workers follow along with push mowers and string, blade weed-eaters or “weed wackers” around trees and shrubs.

String mowers are blamed for most of the unsightly bark injuries. The tree or shrub is eventually weakened by sap leakage and nutrient loss. The damage also exposes the tree/shrub crown to numerous disease infection and insect borers.

A better management practice is to maintain a thin organic mulch zone around the tree or shrub base. The mulch should never be piled up against the trunk. A mulch layer more than 4 inches is not recommended.

Weeds will eventually grow on surface of decaying mulch barrier. Periodically, hoe or hand-pull invading grasses and weeds atop the mulch. An alternative is to spray a weed herbicide such as Round-up™ or an equivalent product according to label directions. When done, add 1-inch of mulch for a fresh clean appearance.

Nativars – New Cultivars Of Native Plants

Posted by Hugh on January 20th, 2014

Improved Serviceberry Nativar ‘Autumn Brilliance’

Nativar is a new term coined by Dr. Allan Armitage, Professor Emeritus from the University of Georgia. It combines the words “native” and “cultivar”. Nativar refers to a cultivar of a native plant. It attempts to excite the horticultural marketplace about new cultivars of native perennial plants, such as blackeyed Susan (Rudbeckia spp.), purple coneflower (Echinacea purpurea), coreopsis (Coreopsis spp.), and many others.

Nativars are native plants that resulted from natural or man-made cross pollination. Many natives have undergone a so-called “facelift”, one that enhances the plant’s appeal or improves past deficiencies such as better flowers or disease resistance. The “new and improved” versions drive new sales of natives to professional landscapers and gardeners. This excites their pop and sizzle at the garden center.

A native tree may not develop good fall color. When an individual plant is spotted in a nursery row or in a forest, the nativar is born, tested, named, and propagated. Plant scientists at the University of Tennessee found anthracnose resistant flowering dogwood (Cornus florida) in a Maryland forest. It was tested, propagated, and named ‘Appalachian Spring’. Since its introduction sales of native dogwoods have increased.

A single nativar may be derived from a large seedling population which possesses wide genetic variability for its ecological surroundings. The nativar may not excel over thousands of acres. For example, a nativar exhibiting deep red fall color may not express this color trait a thousand miles away.

Provenance, where the plant originates, plays an important role. Red maples (Acer rubrum) grow in a wide geographical area in the U.S. and Canada. A cold hardy red maple from Wisconsin will likely not survive a hot humid Georgia summer; a Georgian red maple may not cope with a hard Wisconsin winter. An Oregon red maple nativar with flashy red fall color may fizzle in the southeastern U.S.

Native aster species (Symphyotrichum spp.) grow over a wide geographic area of the eastern U.S. Not all aster nativars planted on a single site will flourish.

Baptisia ‘Purple Smoke’ is hybrid nativar of two species

European Hornbeams Serve As Great Garden Sentinels

Posted by Hugh on January 17th, 2014

Touch of Fall Color on Carpinus betulus 'Columnaris'

Upright European hornbeams (Carpinus betulus cvs.) are versatile small to medium-sized deciduous trees that fit most landscape settings. Depending on which cultivar you select, the tree stands with a narrow vertical profile. It grows 35-40 feet tall and 15-20 feet wide. It’s cookie cutter by design as a street tree or tall narrow hedge.

Hornbeams are best planted in late winter balled and burlapped (B&B) and in any month if container-grown. Tall popular cultivars ‘Fastigiata’ and ‘Columnaris’ are being supplanted by shorter growing ‘Frans Fontaine’.

Leaves are small, dark glossy green on the surface and finely serrated along the edge. Autumn foliage turns golden yellow. Tiny spring flowers and pendulous clusters of samara seeds are ornamentally insignificant. European hornbeam is often nicknamed “muscle wood” or “ironwood” as its smooth gray main trunk is muscular.

Annual growth rate is slow. Hornbeams are long-lived when properly sited and nurtured. They prefer in moist, well-drained, acidic to slightly alkaline pH soil. Full open sunlight or partial 5 to 6 hours of sunlight is adequate. Newly planted trees should be irrigated every 7 to 10 days over the first two summers if summers are unusually dry. Otherwise, hornbeams are moderately drought tolerance. Fertilize young trees in late winter with granular 10-10-10 or equivalent. Pruning is rarely needed except to maintain the narrow upright form.

Young trees may be fashioned into a tall hedge or screen, set out 5 to 10 feet apart. Create a garden arch by planting two rows 8-10 feet apart; bend and attach tree tops (leaders) over time to form a natural archway or hut.

Are Your African Violets Looking OK?

Posted by Hugh on January 14th, 2014

Sickly African violet plant

Healthy African violet plant

African violets (Saintpaulia ionantha) are easy to grow flowering house plants. Modern day varieties sold at supermarkets and plant shops often bloom 8-9 months a year.

Lighting needs are minimal, either from indirect sunlight from an east-facing window or under special “grow lights” 12 hours daily. African violets prefer water at room temperature (65-75 °F). Fill your watering container several days prior to watering to evaporate off fluorides and chlorides in the water.

Common problems with African violets are overwatering and fertilizer scheduling. Feed violets twice monthly, November thru February, with any brand “house plant” fertilizer. Use 1/2 the amount recommended on the package added to water. From March thru October, feed 3-4 times monthly with 1/2 rate solution. You must feed plants without burning roots with fertilizer salts. Once each month leach pots thoroughly, watering pots from above. Repot all plants once a year, generally in early autumn.

Water all plants at same time and never leave pots standing in water more than 1 hour. For old or large plants, a second watering may be occasionally needed as the roots fill the pot and need more. In general, interval between waterings may be 5-6 days. Waterlogged plants are an indicator of poor roots or bug infestations.

Check for mealy bugs. They often start out looking like debris (dust or soil) over the leaf surfaces and petioles. A mealy bug outbreak can build quickly. Applying rubbing alcohol to individual bugs with a cotton swab every 3-4 days should clean up an infestation within a month. Insecticidal soap, applied every 3-4 days, is also effective.

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.