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

‘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

Light a Candle in Your Garden

Posted by Hugh on May 1st, 2011

'Giles van Hees' veronica

Speedwells (Veronica spp.) are long-blooming, easy-care perennials. Speedwells are outstanding for their color rich floral candles (spikes). The candle-like flowers rise like sentinels in the late spring-summer garden and attract lots of butterflies and bees.

The small individual 5- pedaled blossoms range in colors from white, pink, blue, and several shades of purple. The floral spikes open at the base and continue upward. Cultivar sizes vary, making veronicas a great choice as the front, middle or back border in any flower bed. Personal picks include V. ‘Giles Van Hees’ (6- inch bright pink spikes) and V. ‘Royal Candles’ (15-inch blue-purple spikes).

Speedwells belong in full sun, planted in a moist, well-drained soil. Soggy soils may lead to a root rot and foliar mildew diseases. Summer irrigation and mulching aids to conserve soil moisture and suppress weed competition.

Quick removal of the old flower spikes (deadheading) encourages growth of new basal foliage and almost continuous flowering through the summer months. Pruning back taller cultivars by one-third reduces the need for staking plants. Dividing perennial crowns every 2-3 years in early spring maintains overall plant vigor.

Take Flight With The Unique Dove Tree

Posted by Hugh on April 27th, 2011

Dove tree

Up for a challenge. Dove tree (Davidia involucrata) is a medium-size tree from China. Mature dove trees are 30-40 feet in height and 20-30 feet in width. A young tree exhibits a pyramidal form and forms a rounded canopy at maturity. The coarsely textured 4 – 5 inch circular leaves are bright green with no significant fall color, dropping either pale green to brown.

In early May dove tree in bloom is an awesome sight to behold. All attention is focused on the two uneven white bracts, one 7- inches long and 4- inches wide and a second shorter 4- inches long anf 2- inches wide bract. A slight breeze rustling past the two white bracts creates an illusion of dove wings aflutter, earning such pseudonyms like “handkerchief tree” and “ghost tree”. The true ¾- inch wide dome flowers are insignificant.

Ordinarily, you must wait ten or more years for dove tree to bloom the first time (and not every year). ‘Sonoma’ is a new cultivar which flowers reliably within 2 – 3 years after planting and does so annually. As the tree ages, its scaly orange- brown bark offers minor winter interest.

Dove tree need to be properly sited in a moist well-drained loamy soil in the Southern Appalachian region (USDA hardiness zones 6 and 7). Guard against extreme summer heat and winter cold blasts and irrigate during summer dry spells. Disease and pest problems are as rare as dove trees.

Dove tree may be purchased from specialty plant nurseries on the internet or from mail order.

Enjoy a Mite-free Alberta Spruce This Summer

Posted by Hugh on April 23rd, 2011

Mite free Alberta Spruce

A popular saying among gardeners is “the right plant in the right location”. They must be thinking of Alberta Spruce (Picea glauca ‘Conica’). Within a few years after planting, this popular dwarf conifer becomes devastated by spider mite infestations. The rule is to plant Alberta spruce where it receives good air circulation on all sides.

A common mistake is to plant Alberta spruce close to a building foundation. Here, the needle foliage on the backside of the shrub facing a wall or foundation remains wet. Often, the bottom one-third of the plant is covered with morning dew after a rain or from overhead irrigation.

Initial mite feeding damage frequently starts on the sheltered, warmer side of the shrub. Repeated mite infestations lead to localized stem and needle death which causes Alberta spruce to look unsightly. Similar symptoms are observed in other shrub species, including junipers (Juniperus spp.), hollies (Ilex spp.), and hemlock (Tsuga spp.).

A backup plan is to spray susceptible shrubs with a timely pesticide (miticide). A timely coarse pressure spray of tap water in early spring and again in early fall will wash most eriophyid and spruce spider mites off the foliage.

* Thanks to Dr. Donald Booth, Research Entomologist at the Bartlett Tree Laboratory in Charlotte, NC for his assistance.

Wolfeyes Chinese Dogwood

Posted by Hugh on April 20th, 2011

'Wolf Eyes' Chinese dogwood

Chinese dogwood (Cornus kousa) is a popular 20-25 foot tall spring flowering tree which blooms two weeks after our native flowering dogwood (C. florida) has finished. The cultivar ‘Wolf Eyes’ makes a compact 8 to 10 foot tree or large shrub, almost double that in width.

Wolf Eyes displays an awesome leaf variegation which makes it a focal point in any garden or patio container. Its wide white wavy leaf margin is prominently edged on its olive green foliage. Leaf variegation is very stable, rarely reverting to all green. Summer foliage is also burn or scorch resistant, best where planted in partial sun in USDA zone 7 in the Southern Appalachian region.

The off-white four-pointed bracted flowers contribute very little, the small bracts muted by a standout variegated foliage. The green raspberry-like fruit size up and ripen to a reddish orange color beginning in late summer, attracting lots of famished birds to your property.

Chinese (kousa) dogwood prefers a deep, well-drained, slightly acidic soil. While moderately drought tolerant, mulching and summer irrigation during prolonged dry periods is encouraged. Kousa dogwood is very disease resistant.

Gordlinia- Nothing Like it Before!

Posted by Hugh on April 17th, 2011

(x Gordlinia grandiflora 'Sweet Tea')

‘Sweet Tea’ resulted from crossing franklinia (F. alatamaha) and loblolly bay or gordonia (G. lasianthus). Sweet Tea is still abit finicky like franklinia, but is more resistant to Phytophthora disease (soil pathogen). This new intergeneric cross possesses huge (5 inch diameter), showy flowers that look like big fried eggs. Sweet tea exhibits semi-evergreen foliage with large, single, camellia-like flowers from July through September.

Why name it ‘Sweet Tea’? It’s a member of the tea family (Theaceae). The flowers have a light sweet fragrance. Both parent species originate from the South where sweet tea runs in our veins. Sweet tea must be planted a good well-drained soil with even moisture year-round. It grows best in full sun or a little afternoon shade. Irrigation during summer dry spells is a must. Roots readily from stem cuttings, then takes off growing. Mature height is estimated to be 20-30 feet. Winter hardiness is likely in USDA zones 7 thru 10. The plant is not patented or trademarked.

Photo credit and article info. from Dr. Tom Ranney, NCSU Plant Breeder, Mountain Crops Research and Extension Center, Fletcher, NC.