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

Wild Epaulette Tree Can Be Tamed

Posted by Hugh on May 26th, 2011

Epaulette tree

Epaulette tree (Pterostyrax hispida) is a small flowering tree which quickly grows to a mature height of 20—25 feet. Winter hardiness here in the Southern Appalachian region (USDA zones 6 and 7) is no problem. A newly planted tree grows an average of 15-18 inches per year and blooms early.

Epaulette prospers in a moist well-drained soil of moderate acidity (pH 5.5 to 6.5) and in full to partial (6 hours minimum) sunlight. Established trees exhibit excellent heat and drought tolerances. Troubles with diseases and insects are not issues.

In mid- to late May, the oft-white wisteria-like floral panicles emerge, a full two weeks following the appearance of the bold 4 – 7 inch long leaves. Clusters of bell-shaped lemony scented flowers create a good showing as pendulous 5-10 inch long panicles. Many stay hidden beneath the coarse foliage canopy. Individual fringed florets measure small, 1/3 inches in diameter or less. Stringy threads of bristly seed clusters follow and persist well through the winter months, offering little in landscape interest.

Epaulette has a strong propensity to root sucker. It demands a committed gardener to steadfastly remove unwanted suckers and lower branches. Eventually, you can tame the wild epaulette into a handsome small specimen tree in garden or patio areas.

Is Paulownia Invasive?

Posted by Hugh on May 24th, 2011

Paulownia uninvited!!

Paulownia or Empress tree (Paulownia tomentosa) is a medium to large 30-50 foot tree. It is extremely fast growing, brittle wooded tree, as much as 4 feet per year. Across the Southern Appalachian region (USDA zones 6 and 7), the large pale violet flowers of paulownia are easily visible in May, perched on branch tips.

Its enormous 10-12 inch large medium green leaves are pushing out at the same time. The leaves dump considerable litter beneath the tree in the fall. Fall foliage color is of little importance.

Paulownia is an exotic from China which many plant experts have labelled “invasive”. A large paulownia tree produces many thousands of viable seeds which are dispersed by wind. The seeds are very susceptible to damping off disease (Pythium) and many do not survive. Seeds do germinate on “sterile” soil such as recently cleared ground and burned areas.

Paulownia is rarely seen in open fields already containing vegetation, compared to other serious invasives such as tree-of-heaven, privet, honeysuckle, et.al. It may grow on the edge of forests, but does not survive or compete in woodland shade.

Paulownia wood is highly prized by the Japanese for furniture, cooking utensils, owls, etc. There are several growers in the Southeastern U.S. who grow the fast growing paulownia wood for its export value.

Yellowwood Not Every Year Bloomer

Posted by Hugh on May 22nd, 2011

Yellowwood's gray beech-like bark

American yellowwood (Cladrastis kentukea) is a medium-sized flowering tree. In the month of May, a beautiful yellowwood tree is in bloom somewhere in the Southern Appalachian region (USDA zone 6 and 7). The 1- 1 1/2 inch white pea blossoms comprise the 8-14 inch long wisteria-like panicles which drape from branch and twig tips.

Yellowwood may bloom 2 to 3 consecutive years and not flower again for 1 to 2 years. The triggering mechanism for flowering is not clearly understood. A complex of environmental and physiological factors may be involved.

Over the past two decades the weather across the Southern Appalachian region can only be described as “extreme”, unusually dry, hot summers and unseasonably mild winters. A physiological condition called “biennial bearing” may be in play here. If a tree sets an unusually heavy seed load one summer, few to no flowers are initiated the following spring.

Whether it flowers or not, yellowwood makes a fine landscape shade tree for any sized landscape. Plant in well drained, slightly acidic soil in full sunlight. Its dark green compound leaves remain pest free from spring until early autumn. Yellowwood’s bright yellow fall color arrives at a time when many trees have already defoliated. Its smooth gray colored bark is very beech-like and has multi-seasonal interest.

Summer Wine™: The Taming of The Ninebark

Posted by Hugh on May 19th, 2011

Physocarpus 'Summer Wine'

Over the past 25 years our native Eastern ninebark (Physocarpus opulifolius) has been reborn. Its overly vigorous nature has been tamed. Latest up is Summer Wine™ ninebark with small, deeply cut, wine burgundy leaves, quite different from the medium green foliage of old-fashioned ninebarks. Summer Wine is a more compact (5-6 feet in height and width) grower.

Grow ninebark in full sun to retain its reddish leaf color longer. Ninebark grows in any soil type, tolerates wet soggy ground, and is pH insensitive. It demonstrates exceptional heat and drought tolerance after one year in the garden. Annual pruning, right after spring flowers have faded, further limits growth and presents many design choices.

Summer Wine fits a multiple of landscape uses: grouped enmasse as a dense growing deciduous hedge, screen or border, or grown by itself as a landscape specimen or in a patio container. Ninebark grown in outdoor containers is winter hardy here in the Southern Appalachian region (USDA zones 6 and 7).

White spirea-like flower clusters, 1 ½ – 2 inch wide, open in May. White blossoms and dark foliage playoff each other. The reddish leaf tint has bled out by mid-summer, now dark green and usually blemish-free. Autumn leaf color is of no consequence.

Select Hollies for Privacy

Posted by Hugh on May 16th, 2011

: Ilex opaca ‘Greenleaf’

I continue to witness the overplanting of Leyland cypress (Cupressocyparis x leylandii) across the Southern Appalachian region (USDA zones 6 and 7). This is followed by Japanese cedar (Cryptomeria japonica) and western arborvitae (Thuja x plicata). These three evergreen species have a rapid growth rate and eventually attain heights of 40-60 feet, sometimes in less than 20 years. Ask yourself the question: “do you really need a huge green barrier around your property?”

Hollies offer the benefits of lustrous green foliage and colorful fruit. The following evergreen species create a dependable privacy screen: Dwarf Burford holly (I. cornuta ‘Dwarf Burford’), Inkberry (I. glabra), American holly (I. opaca), Foster #2 holly (I. x attenuata), and Nellie R. Stevens holly (I. x ‘Nellie R. Stevens’).

A few simple tips about growing hollies:

Hollies prefer a slightly acidic, well-drained, and organically rich soil.
Hollies prefer full to partial sun location.
Established hollies demonstrate good drought tolerance.
Space plants a minimum of 12 feet apart.
Hollies should be properly mated. Fruit are produced on female cultivars and a matching male pollinator should be planted.

‘Janet Blair’ Rhododendron

Posted by Hugh on May 13th, 2011

'Janet Blair' rhododendron

Here in the Southern Appalachian region (USDA zones 6 and 7) rhododendrons can be challenging. Of critical importance is to choose a good garden spot and to plant a hardy cultivar. Over the past 25 years ‘Janet Blair’ has been one of the most reliable varieties in my Northeast Tennessee garden.

‘Janet Blair’ bears medium-sized light pink flower trusses. Individual flowers hold a frilled edge, a golden eye bronze center, and are light fragrantce. ‘Janet Blair’ grows vigorously and is very heat and drought tolerant, averaging six feet in height and spread after 10 years. It branches well, exhibiting a mounding growth habit with glossy green foliage.

Whether your garden soil is sand, silt, or clay, generously amend it prior to planting with peat moss and compost. The soil must be moderately acidic (pH below 5.8) and well drained. Mulching after planting aids in soil moisture retention, reduces weeds, and helps cool shallow rhododendron roots.

Like most rhodies, Janet Blair needs partial protection from harsh afternoon summer sun and drying winter winds. Irrigate newly planted rhododendrons during the first two summers to insure their long term survival. Pruning is rarely necessary and is best performed within one month after blossom fall. Removing spent flowers promotes new growth.

‘Janet Blair’ is a Dexter hybrid originated by David Leach.

Growing Azaleas in Outdoor Containers Year-Around

Posted by Hugh on May 10th, 2011

'Elsie Lee' azalea (photo by Sam Kinsey)

In the Southern Appalachian region (USDA zones 6 and 7), if you desire to grow azaleas in above ground containers year around, you must select winter hardy cultivars. Two of the best for containers are ‘Elsie Lee’ (2½- inch wide semi-double light lavender blooms) and ‘Herbert’ (1 ¾- inch wide bright purple with dark blotch). ‘Elsie Lee’ boasts a neat, compact shrub form while ‘Herbert’ has a dense, slightly more spreading habit.

Both exhibit exceptionally long flower period. Spring – summer leaves are medium green, changing to bright yellow, orange, and/or red shades in the autumn. They’re mid-season bloomers and vigorous growers, attaining 3-4 feet in height and width in 10 years.

Grow azaleas to keep roots cool inside the lightly colored (not black) containers. Follow a regular watering and nutrient feeding schedule to establish a deep, extensive root system. Pot in a well drained peat and bark based potting soil or medium with a 2-3” surface layer of mulch. Feed with an acid-based liquid fertilizer like Miracle-Gro™ or Miracid™. Prune azaleas as needed to shape plants and to eliminate dead or diseased twigs.

‘Elsie Lee’ is a Tony Shammarello hybrid from Ohio. ‘Herbert’ azalea (R. yedoense var. poukhanense x R. ‘Hexe’) is a fabulous David Gable hybrid from Pennsylvania. Bred more than 50 years ago, they’re winter hardy to -15 degrees F (USDA Zones 5-9).

Stop Ignoring Enkianthus

Posted by Hugh on May 7th, 2011

'Red Bells' enkianthus

From the photo, looks like a pieris? No, it’s redveined enkianthus (Enkianthus campanulatus) and its brightly colored bell-shaped flowers are attention getters in the early May garden. Lovely cream yellow to orangy red bell shaped flowers are faintly red veined. The bell shaped blooms exude a slight scent, one that you may like or not.

From the start, growth rate is slow, but once established, shrubs mature to 8 to 12 feet in height and about the same in spread. Culture is similar to azaleas, pieris and rhododendrons which they are related to. Enkianthus grows well in full sun to light shade. They are not as fussy regarding pH and moisture needs, provided the soil is well drained. Enkianthus becomes well established within two years, and are rated as moderately drought tolerant. Do provide supplemental irrigation during the driest periods of summer.

Over twenty cultivars are listed, varying in flower colors from near white (pale cream), pink and red. Fall color is quite variable among vcultivars and growing site from yellow, orange or red. Enkianthus has no serious disease or insect problems.

“Mary, Mary, How You Do Grow in My Garden”

Posted by Hugh on May 4th, 2011

'My Mary' deciduous azalea

‘My Mary’ is a hybrid deciduous azalea (R. ‘Nacoochee’ x R. austrinum) ending its flowering cycle in my spring garden. ‘My Mary’ has been a steady performer, averaging 4-5 feet in height in 10 years. Its clusters of bright yellow orange tubular flowers measure 2 1/2” across. Its early morning sweet fragrance is a gentle hint for me to take notice.

‘My Mary’ is one of several native deciduous azaleas which thrive in the Southern Appalachian region (USDA zones 6-7). They’re really native rhododendrons and grow best in a well-drained acidic soil richly amended with compost. Provide young azaleas weekly irrigation during their first two summers for plants to become established after two years. Native azaleas are quite heat and drought tolerant after their period of adjustment.

‘My Mary’ grows best planted in dappled sunlight or high open shade. Protection from strong winds reduces winter bud desiccation. Proper soil drainage avoids potential root rot or “wet feet”problems. Planting azaleas in raised garden bed benefits.

Azaleas benefit from organic mulches (wood or bark chips, shredded leaves or pine needles) to conserve soil moisture and moderate soil temperatures. Test your soil every 4-5 years to insure an acidic pH lower than 5.8. Acidic fertilizers like Miracle Gro™ and Miracid™ are excellent sources of both major and minor nutrients.

‘My Mary’ was introduced by Transplant Nursery in Lavonia, GA.

Callaway Gardens

Posted by Hugh on May 2nd, 2011

Perhaps, azaleas (Rhododendron spp.) offer the broadest color array of any shrub category in the spring garden. Very few public or private gardens display azaleas better than Callaway Gardens in Pine Mountain, GA. In late March, Jane and I enjoyed a 2-day visit at Callaway.

We arrived to catch the early blooming azalea sequence and were not disappointed. Vivid reds, pinks, and whites surrounded us in Callaway’s Azalea Bowl and Overlook Azalea Garden. Azalea series labelled Kurume, Glendale, Girard, Encore, and a lovely white cultivar labeled ‘H.H.Hume’ were stunning. The pale pink native Piedmont deciduous azaleas (R. canescens) were also starting to open. Azalea bushes in the hundreds were in bloom and many thousands more awaiting their turn over the five week of Callaway’s Annual Azalea Festival.

'H. H. Hume'

Many early flowering perennials, woodland beauties, shrubs and trees joined the spring floral chorus. To list just a very few: Oriental cherries, ornamental pears, dogwood, forsythia, several viburnum species, trilliums, Jack in the Pulpits, woodland poppies, and Lenten roses. Hundreds of Japanese maples (Acer palmatum) and (A. japonicum) complimented the azaleas. Azaleas and Japanese maples do make a perfect pair.

Not a gardener? Callaway is a visual masterpiece with hundreds of acres to be enjoyed by outdoor and sports enthusiast from golfing, tennis, swimming, biking, hiking, and fishing. We also stopped at the Sibley Horticultural Center and Day Butterfly Center at Callaway. A Birds of Prey show is presented daily at the Discovery Center Amphitheater.

You may pre-register for a scheduled cooking or gardening class. There are additional workshops held throughout the year. Several moderately priced restaurants are on the property or in nearby towns. For further information go to the Callaway Gardens website: www.callawaygardens.com