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

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.

Three New Spreading Junipers Waking Up Landscapes

Posted by Hugh on November 9th, 2013

'Daub's Frosted' Juniper at UT Gardens in Knoxville

In times past Chinese junipers (Juniperus chinensis) were popular foundation shrubs and ground cover (USDA hardiness zones 4-9). They were popular choices in sunny locations for erosion control and around seashore areas. Three exciting cultivars have arrived on the landscape scene and should bring junipers back in vogue.

Angelica Blue Chinese juniper (J. chinensis ‘Angelica Blue’) grows 5 to 6 feet high and 6 to 7 feet wide with bright blue-green needles. Introduced by Angelica Nurseries, it exhibits a compact horizontal form.

Daub’s Frosted Chinese juniper (J. chinensis ‘Daub’s Frosted’) has a low ground-hugging habit that grows 1 to 2 feet high and 3 to 6 feet wide. It struts bluish green foliage frosted with new yellow tip growth in the spring.

Gold Lace Chinese juniper (J. chinensis ‘Gold Lace’) grows 4 feet high and 5 feet wide with vibrant gold foliage.

In general, junipers grow in average well-drained soils with moderate moisture. Junipers are best planted in full open sunlight where air movement should reduce the threat of a disease outbreaks. Shady areas and wet soils are not where junipers belong. Pruning may be needed to maintain the height and spread of many vigorous cultivars.

Following a short one year establishment span, the new junipers listed above tolerate shallow dry soils and resist coastal salt and urban air pollutants. Juniper fruits may look like berries, but are actually small scaly cones.

Junipers suffer from no serious disease or pest problems. Avoid juniper tip and needle blights by selecting resistant cultivars and following proper irrigation practices. Occasional insect pests include aphids, bagworms, webworms, and scale. Deer have no taste for junipers.

Kentucky Coffee A Superior Large Native Tree

Posted by Hugh on November 4th, 2013

K Coffee Tree at Kingwood Center

Platy Bark of K-Coffee Tree

Kentucky coffeetree (Gymnocladus dioicus) is a large native tree found in 18 states, from New York west to Nebraska and from central Minnesota south to Oklahoma (zones 4 through 7). It reaches a mature height of 70 feet (some greater than 90 feet) with a spread of 50 feet. Established in 2-3 years, annual growth rate averages 12-15 inches, about the same as ginkgo or white oak.

Late appearing foliage emerges in mid- to late spring. Recessed vegetative buds push forth multi-pinnate compound leaves. A single leaf can be 2 to 3 feet long, producing between 70 and 100 leaflets. Fragrant olive-white flower panicles appear in late May in clusters of 8 to 12 inches long by 3 to 4 inches wide.

In autumn its lime-yellow to golden brown compound foliage falls to become a leaf raker’s nightmare. During the winter months, the totally naked upright branches take on the appearance of an arboreal horror from a Stephen King novel. K-coffeetree may be single or multi-trunked.

K-coffeetree grows in a wide variety of soil types and is tolerant of poorly drained (wet sites). No significant disease or insect pests mar the lush green tropical-like summer foliage. Bark is distinctively charcoal gray and shaggy, a trait more pronounced as the tree ages.

Spring pea-like flowers are dioecious, bearing either male or female flowers. Female trees bear clusters of distinctive bean pods measuring 5 to 10 inches long and 1 ½ to 2 inches wide on the tips of the branches. Flowers and pods are inconspicuous, mostly hidden within the dense foliage through late summer.

‘Espresso’ is a male cultivar with no seed pods to rake up. In colonial America the beans were harvested and a crude coffee extract was brewed, no threat to Folgers® and Maxwell House® today. The leaves and bean seeds are reportedly toxic to man and grazing cattle.

K-coffeetree is rarely sold in garden centers, but available on-line. It is notoriously difficult to transplant, but young 2-inch caliper nursery-grown trees thrive.

Burning Bush Turns Fire Engine Red In The Fall

Posted by Hugh on November 1st, 2013

Clipped hedge of Euonymus alata 'Compactus'

Be cautioned from the start that planting dwarf burning bush (Euonymus alata var. compactus) in some states in the U.S. is prohibited. This deciduous shrub is known for its awesome fire engine red fall foliage color (USDA hardiness zones 4 to 8). In shady areas fall leaf color tends to be more pinkish. Fall leaf color is spectacular most years, hence the common name “burning bush”.

This popular shrub grows in average well-drained soil and in full sun to part shade. ‘Compactus’ is not very compact, actually a vigorous grower. It tolerates heavy pruning, including tight hedging. If left unchecked, a single shrub grows mound-like, 10 feet tall and equal or greater in spread.

Small yellowish-green flowers appear in May but most are hidden within the dense foliage. Small red fruit capsules, less than ½ inch in diameter, appear in fall and most are not visible against the crimson red foliage.

Corky ridges (called ‘wings”) line the bark, a simple way to identify this shrub in the winter. The wings or ridges are not prominent on ‘Compactus’ and almost non-existent on very dwarf forms. Dwarf cultivars ‘Rudy Haag’ and Little Moses® may grow 3-4 feet tall and 4-5 feet wide in 15-20 years. Flowers of the latter two cultivars produce few, if any, viable seeds and are less of an invasive threat.

This utility shrub has few serious insect or disease problems. Occasionally, it becomes infested with dreaded euonymus scale, which is managed by applying dormant and summer oils (organic option) or any of several contact insecticides.

Dwarf burning bush is utilized as a single specimen or grouped together as hedges, privacy screens, or foundation shrubs.

Invite These “Bells” To Next Spring’s Garden Ball

Posted by Hugh on October 30th, 2013

Spanish Bluebells and Microbiota in Conlon Garden

Fall planting of many kinds of bulbs is a worthwhile long term investment of your time. Many bulbs (and corms) like daffodils and crocuses will naturalize where you plant them. They also bloom for long periods from late winter into spring. Bulbs bloom nice their first spring; flower heavier the second year; and multiply each succeeding year.

Two bulbs that are underplanted are Spanish bluebells (Hyacinthoides hispanica) and summer snowflakes (Leucojum aestivum). They naturalize and thrive in compost rich moist soil. In zone 6 and further north, sow them in full sun; plant them where they receive afternoon shade in the hot Southeastern U.S.

Spanish bluebells (USDA hardiness zones 4 through 10) bloom in the late spring in full sun or partial shade. Their dainty bluebell flowers are supported on sturdy stems and are excellent as cut flowers. The cultivar ‘Excelsior’ is a rich darker blue than other cultivars, and stand slightly higher to 12 inches.

According to Becky Heath, co-owner of Brent and Becky’s Bulbs in Gloucester, VA, the popularity of summer snowflakes (USDA zones 4-8) have increased over the past 20 years. ‘Gravetye Giant’ is one of her favorites; they are exceptionally vigorous and naturalize rapidly. Their white lily of the valley blooms are large and showy in April / May garden. Plants grow 2 feet or more in full sun or part shade. The fragrant nodding white bells are tipped with light green dots.

Willow Oak Very Reliable As Street Or Park Tree

Posted by Hugh on October 28th, 2013

Willow Oak in TN parking lot

Mid-autumn foliage of willow oak

Willow oak (Quercus phellos) is medium to large, deciduous tree, part of the red oak group. It is noted for willow-like oak foliage and growth rate after a 2 year establishment period is moderate (USDA hardiness zones 5-9).

Willow oak grows 50-75 feet tall and 30-35 feet wide with a rounded top or canopy. Young trees tend to be pyramidal in form. Individual specimens may reach 90 or more feet under ideal site conditions. Its small ¼ – ½ inch nearly round acorns form almost every year, are not a major maintenance headache, and serve as an important food resource for wildlife.

Long stringy yellow-green long catkin flowers appear in April, a few days before leaves emerge. The unlobed 5-inch long leaves mimic those of willow trees (Salix spp.); leaves are tipped with a single 1-inch wide bristle. Green summer leaf color turns an undistinguished yellow-brown or dull gold very late in autumn. A young tree has a smooth grayish bark which darkens and becomes furrowed with age. From the latin word “phellos”, the species name means cork — because bark on older trees tends to be hard and corky.

Native to the Southeastern United States, willow oak prefers a moist bottomland, organically-rich, and well-drained soil. It tolerates light shade, but performs best in full sun. Willow oak can handle a wide range of soils including clay. Once established, it copes with summer drought well. Foliage is tolerant of urban air pollution.

Willow oak demonstrates good disease and pest resistance and is a long-lived and low-maintenance tree. In a landscape willow oak fits into large sites, such as in public parks or along wide roadways and avenues with good soil mass for adequate moisture. The narrow leathery leaves abscise very late in the fall and make a great loose mulch scattered under other landscape plants.

Better Red Fall Leaf Color On American Hornbeam

Posted by Hugh on October 21st, 2013

Firespire™ Hornbeam from Johnson Nursery, Menomonee Falls, Wisc

Fall Leaf Color of Firespire™ American hornbeam

American hornbeam (Carpinus caroliniana), aka ironwood or muscle wood, grows primarily in moist, slightly acidic soils along woodland rivers and streams (USDA hardiness zones 3-9). This native hornbeam adapts to either wet or dry ground as long as soil moisture drains adequately. It copes with tough urban conditions including on non-irrigated parking lots and on the outer edge of rain gardens. It grows equally well in full sun or partial shade.

Its autumn foliage turns intense shades of yellow, orange, and rarely scarlet, depending on soil pH and the provenance of the species. Over the past quarter century Johnson Nursery (primarily wholesale and retail locally) in Menomonee Falls, Wisconsin have selected several good fall red foliage forms. Firespire™ is a grafted clone with semi-upright branching and vibrant red fall color. ‘J N Strain’ is a known seed population which delivers above average red fall leaf color.

Ironwood blooms in spring as separate male and female catkins. In autumn female catkins form showy clusters of winged nutlets, that is an important food resource to numerous forest fauna. Its beech-like muscular bark covers the main trunk and branches as a singular trait in the winter garden.

American hornbeam grows 25-40 feet tall and variable in width depending on cultivar. It commonly grows multi-stemmed and is free of disease and pest problems. The rich green summer and colorful autumn foliage plus attractive gray muscular winter bark makes it an excellent small patio tree. Or mass several together to create a deciduous privacy screen.

American hornbeam is more difficult to transplant than its taller European counterpart (C. betulus).

Fall Is Spring Bulb Planting Time

Posted by Hugh on October 18th, 2013

Mix of Tulips and Pansies at Callaway Gardens

If you love spring flowering tulips, daffodils and other spring-flowering bulbs, some planning and planting chores should be set into motion this fall. Spring flower bulbs should be planted when cool soil temperatures (below 55 °F) return. For gardeners living in the Southern Appalachian region (USDA hardiness zones 6 and 7), bulb planting begins in early October and ends when the ground freezes or around the first of the New Year.

Bulbs and corms (ex. crocus) should spend the winter in the cold moist ground. They may also be potted in moist soil-less media and stored in a refrigerator for 90 days or more. This mimics the outdoor garden environment. Refrigerated bulb pots can be forced to bloom indoors in February and March. Cover the pots with shrink wrap or in plastic bags to prevent the potting media from drying out or foul smelling your refrigerator.

If you have lots of bulbs to plant in the garden, invest in a power drill and an augur. Most garden centers sell augur bits. This tool makes bulb planting alot easier physically. A recommended depth chart should be available where you purchased the bulbs. Mark the proper depth on the augur with tape. After 5-6 holes, you’ll become a planting pro.

If the bulbs are planted before October 15th, consider inter-planting with winter hardy pansies and violas. Pansies will guarantee a blast of color from fall into late spring while you’re waiting for bulbs to poke through in late winter.

If you can’t plant bulbs right away, store them in a cool, dry place with good air circulation. If you purchased bulbs earlier and found them partially sprouted in the garage, plant them immediately, even if you need to use a pick axe in an icy soil. Most should come up and bloom feebly the first year.

Popular Landscape Trees Deer Don’t Like

Posted by Hugh on October 15th, 2013

Red Buckeye

Flowering Dogwood

This title is somewhat misleading. Deer will eat or sample (nibble) on any landscape plant, particularly if they are hungry enough. Deer also do not read lists of plants they’re suppose to leave alone.

The following list of deer resistant plants is a sampling from reports across the U.S. It does not include every tree reported. Deer species and numbers vary across this big country. A deer’s food palate may also differ from one region to another. It also depends on how hungry the numbers of deer in an area may be.

Some native trees such as American beech, buckeyes, green ash, persimmon, hophornbeam, and flowering dogwood are important food resources for deer and other wildlife. But, they do little significant damage to their host tree(s). If you are trying to introduce young host trees into a landscape, you should fence them off for 3-5 years until they become larger and better established. Finally, prune up low branches out of reach of deer feeding.

Abnormally high deer populations starved for a lack of their favorite foods (mast) will eat or browse on almost any plant. This is a survival reaction. To truly protect plants from deer when deer numbers are unusually high, a tall fence or reinforced netting may be your best options.

Deer Resistant Tree List:

Paperbark Maple (Acer griseum)
Japanese Maple (Acer palmatum)
Striped maple (Acer pensylvanicum)
Norway Maple (Acer platanoides)
Red Maple (Acer rubrum)
Sugar Maple (Acer saccharum)
Ohio Buckeye (Aesculus octandra)
Red Buckeye (Aesculus pavia)
Mimosa (Albizia julibrissin)
Downy Serviceberry (Amelanchier arborea)
Shadblow (Amelanchier canadensis)
Allegheny Serviceberry (Amelanchier laevis)
Pawpaw (Asimina triloba)
Himalayan Birch (Betula jacquemontii)
Yellow Birch (Betula lutea)
River Birch (Betula nigra)
Paper Birch (Betula papyrifera)
European White Birch (Betula pendula)
European Hornbeam (Carpinus betulus)
Deodar Cedar (Cedrus deodara)
Katsura Tree (Cercidiphyllum japonicum)
Chinese Fringe Tree (Chionanthus retusus)
Flowering Dogwood (Cornus florida)
Chinese (Kousa) Dogwood (Cornus kousa)
Winter King Hawthorn (Crataegus viridis ‘Winter King’)
Japanese Cedar (Cryptomeria japonica)
Leyland Cypress (Cupressocyparis x leylandii)
Persimmon (Diospyros virginiana)
American Beech (Fagus grandifolia)
European Beech (Fagus sylvatica)
Green Ash (Fraxinus pennsylvanica)
Ginkgo (Ginkgo biloba)
Honey Locust (Gleditsia triacanthos)
Carolina Silverbell (Halesia diptera)
American Holly (Ilex opaca)
Eastern Red Cedar (Juniperus virginiana)
Goldenrain Tree (Koelreuteria paniculata)
Tulip or Yellow Poplar (Liriodendron tulipifera)
Southern Magnolia (Magnolia grandiflora)
Dawn Redwood (Metasequoia glyptostroboides)
Eastern Hophornbeam (Ostrya virginiana)
Sourwood (Oxydendrum arboreum)
Spruces (Picea spp.)
Japanese Red Pine (Pinus densiflora)
Limber Pine (Pinus flexilis)
Eastern White Pine (Pinus strobus)
Flowering Cherry (Prunus serrulata)
Douglas Fir (Pseudotsuga menziesii)
Sassafras Tree (Sassafras albidum)
Bald Cypress (Taxodium distichum)