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

Lenten Roses Perk Up the February Garden

Posted by Hugh on February 2nd, 2011

Helleborus x hybridus

Lenten roses or hellebores (Helleborus spp.) are long-lived perennials, often surviving in the same garden spot for many years. Four species of Lenten roses grow in the Southern Appalachian region (USDA hardiness zones 6 and 7). All thrive in shady garden recesses, exposed to as little as 3 – 4 hours of dappled sunlight. Numerous new cultivars have been introduced over the past 25 years.

Foliage is coarsely tooth, palmately compound, the leaflets arranged like fingers on a hand. Lenten roses bloom from mid-February through April and are available in white, pink, green, plum or reddish-purple.

Lenten roses love a loamy well drained soil rich in organic matter or compost. A limey soil pH around 7.0 or slightly higher is best. Mulching around plant(s) contributes to their garden longevity. Hellebores are drought tolerance, but regular watering during dry summer periods is encouraged.

Plants should be divided every 4-5 years either in the early spring, soon after flowering, or in early fall. Wear when handling seeds or plants as the sap may cause skin blisters. Lenten roses are highly poisonous to most animals, including humans, and are quite resistant to deer and vole feeding.

Most popular is the Oriental hellebore (H. x orientalis, often written H. x hybridus). They offer the most color choices of any species. Flowers average 3-inches in width and heads are slightly nodding. Flowers are borne on single stems and petals are often spotted or flecked.

Next Blog: The Other Lenten Roses

Disease-free Shrub Rose Trial–The Winners Are…

Posted by Hugh on January 30th, 2011

: Blushing Knockout™

Over the past 10 years, the world of roses has witnessed a revolution with the popularity of the Knockout™ series of roses in gardens across the U.S.

Over the past 5 years the University of Tennessee has been testing shrub roses in Poplarville, MS and two Tennessee locations. Dr. Mark Windham and his research team have been evaluating disease resistance in shrub roses. “The summer heat and humidity in the South makes it a perfect location for evaluating rose disease resistance”, says Dr. Windham.

The winners in the 2010 UT Shrub Trial are:

Category 1. Resistant Cultivars (<2% foliage with blackspot and/or Cercospora leaf spot):

‘Blushing Knockout’

‘Brite Eyes’

‘Double Knockout’

‘Double Pink Knockout’

‘Golden Eyes’

‘Hansa’

‘Kashmir’

‘Knockout’

‘Moje Hammarberg’

‘My Girl’

‘Pink Knockout’

‘White Dawn’

‘Wildberry Breeze’

Category 2. Moderately Resistant )<10% foliage with blackspot and/or Cercospora leaf spot):

‘Carefree Sunshine’

‘Como Park’

‘Fiesta’

‘Forty Heroes’

‘Homerun’

‘My Hero’

‘Palmengarten Frankfurt’

‘Super Hero’

‘Wild Spice’

‘Wild Thing’

Most, if not all cultivars, may be purchased from mail order nurseries found on the internet. The ‘Knockout’ series and ‘Home Run’ cultivars are available at most garden centers.

Re-Blooming Your Poinsettia: Winter thru Summer Care

Posted by Hugh on January 27th, 2011

'Prestige' poinsettia

Part III: By late January your poinsettia plant may look droopy and the leaves pale green. Some flowers (colorful bracts) and leaves may have dropped. To revive the plant and to program it to flower again next winter requires additional care from you starting now.

Move the plant to an east or south exposure window, offering it as much direct sunlight as possible. Keep the room temperature between 68-75°F during the day and no lower than 55°F at night. Avoid cold window drafts. Water the plant 1-2 times weekly, and never allow the plant to sit in water. If leaves shrivel and drop, you may be under/over watering it. Keep room humidity high, but do not mist the plant directly.

In early March repot into a slightly larger container, adding new potting soil. Cut the plant back by two-thirds to stimulate all new shoot growth. Feed every 2-3 weeks with a water-soluble plant fertilizer according to label directions.

By late April move the poinsettia outdoors under partial shade when daily temperatures hover above 55°F and bring it back indoors when evening temps drop.

By mid to late May the poinsettia is safe to move permanently outdoors. Set the poinsettia on a partially sunny (not direct sun) deck or patio area or under a shade tree. Continue to fertilize every 2-3 weeks.

From June thru September 10th, pinch growing tips back 2-3 inches every 3-4 weeks to develop a well-branched compact plant. If not pinched, the plant will grow tall and spindly. Continue watering and fertilizing until mid-September when plant is brought indoors to initiate re-blooming.

Previous Blogs about Care of Poinsettias (dated: 12/18/10 and 12/20/10). Part IV-“Steps in Re-blooming Your Poinsettia” will be published in September.

Two Sensational New Oakleaf Hydrangeas

Posted by Hugh on January 24th, 2011

'Ruby Slippers' oakleaf hydrangea

Oakleaf hydrangea (Hydrangea quercifolia) is a popular native shrub in the Southeastern U.S. (USDA hardiness zones 5 to 8). Two new compact forms of oakleaf hydrangea were recently introduced by the U.S. National Arboretum.

In early summer, ‘Ruby Slippers’ is covered with 9-inch-long floral clusters that are held upright above the foliage. ‘Ruby Slippers’ grows to about 3 ½ feet tall and 5 feet wide and has large creamy white flower panicles that mature to a deep rose color in late summer. ‘Munchkin’ is slightly smaller at 3 feet tall and 4 ½ feet wide, and 6 ½ inch long white flowers age to a medium pink color. Both cultivars grow in either light shade or full sun.

Their compact form and dense plant habit make it ideally suited for use in small residential landscapes. The new light green foliage in spring turns dark green in summer and mahogany-red in fall. Both are ideal specimen shrubs planted either individually or together as a lovely deciduous hedge row.

‘Ruby Slippers’ and ‘Munchkin’ were developed by Dr. Sandra Reed, plant breeder at the U.S. National Arboretum Research Lab, located at the Tennessee State University Nursery Research Center in McMinnville, TN.

2012 Perennial Plant of the Year Named

Posted by Hugh on January 21st, 2011

Brunnera 'Jack Frost'

The Perennial Plant Association (PPA) has selected Brunnera macrophylla ‘Jack Frost’ as the 2012 Perennial Plant of the Year. Runnersup for 2012 honors were Panicum virgatum ’Northwind’, Heuchera ‘Caramel’ and Chelone lyonii ‘Hot Lips’.

Brunnera ‘Jack Frost’ foliage is deer resistant. It grows to a height and width of 12-15 inches. Its silvery foliage stands out in a shade garden. Brunneras produce racemes of blue star-like flowers in mid to late spring.

Grow ‘Jack Frost’ brunnera in a compost-rich, well-drained soil. Water plants regularly during summer dry spells. Mulching around plants also benefits.

Brunnera inhabits the shade garden alongside other favorites such as hostas (Hosta spp.), lungworts (Pulmonaria spp.), coralbells (Heuchera spp.) and variegated Solomon Seal (Polygonatum odoratum ‘Variegatum’).

Brunnera ‘Jack Frost’ was commercially introduced in 2000 by Walters Gardens in Zeeland, Michigan.

Reminder: The 2011 Perennial Plant of the Year is Arkansas Bluestar (Amsonia hubrichtii)

Stop the Leyland Madness

Posted by Hugh on January 18th, 2011

Leylands Gone Wild!

Leyland cypress (x Cupressocyparis leylandii) is a tall, fast growing evergreen tree or shrub. Many are planted as privacy screens. Ask yourself, should you really plant a 50 foot barrier between you and your neighbor(s)?

In the Southern Appalachian region (USDA hardiness zones 6 and 7), there are shorter and better evergreen choices. In the 12-16 foot category:

Boxwood (Buxus spp. and hybrids)

Plum yew (Cephalotaxus harringtonia) ‘Fastigiata’

Hinoki cypress (Chamaecyparis obtusa)

Japanese falsecypress (Chamaecyparis pisifera)

Dwarf Burford holly (Ilex cornuta ‘Dwarf Burford’)- clipped

Inkberry (Ilex glabra)

Foster holly (Ilex x attenuata)- clipped

American holly (Ilex opaca)- clipped

Nellie R. Stevens holly (Ilex x ‘Nellie R. Stevens’)- clipped

Skip laurel (Prunus laurocerasus ‘Schipkaensis’)

Yew (Taxus spp.)- upright or fastigiate forms

Eastern arborvitae (Thuja occidentalis)

Leatherleaf viburnum (Viburnum rhytidophyllum)

Prague viburnum (Viburnum x pragense)

Leyland cypress is susceptible to three serious canker diseases, in which pruning is the principal curative remedy. Leyland is also susceptible to bagworms. Their enormous growing height makes pesticide spraying and pruning options almost impractable and costly.

From the start, don’t plant leylands closer than 12 feet apart (recommend 16 feet spacing). Plants will touch within 4 years after planting. During the first three summers, young leylands require deep watering as they’re not drought tolerant. A 2-3 inch mulching depth in the row aids in conserving soil moisture.

Planting Trees for Future Generations

Posted by Hugh on January 15th, 2011

A Lovely Blackgum in Winter

Oaks, beeches, hickories, ginkgoes, bald cypresses, redwoods, chestnuts and others are trees that future generations inherit from previous generations. In human terms, it takes a lifetime to grow an acorn into a mighty oak. Many tree species live hundreds of years, often asking little and contributing much beauty, summer cooling shade, winter heating comfort as windbreaks, and a food source for birds, insects, and other animals.

Select seeds from trees of exceptional parent stock. You may want to collect acorns around an historical site, such as Andrew Jackson’s Hermitage near Nashville, TN or Thomas Jefferson’s Monticello just outside Charlottesville, VA. Pick seeds or nuts from a parent or grandparent’s property.

If you are asked to serve on a tree planting project this spring, do volunteer, not only at digging time, but on the summer maintenance detail. Young trees need nurturing as do young children. When summer is at its hottest and driest, you should be standing by the tree(s) with hose in hand. Apply or refreshen the mulch around the tree(s) to reduce potential weed competition and also to conserve soil moisture.

Frequently, the concept of “mightier than an oak” begins in the mind and caring hands of a gardener like yourself.

Hardy Dwarf Deodara Cedars

Posted by Hugh on January 13th, 2011

'Glacier Blue' Deodara Cedar

Over the past ten years, deodara cedar (Cedrus deodara) has carved its niche into Southern Appalachian gardens (USDA zones 6 and 7). Three zone 6 hardy dwarf cultivars, ‘Glacier Blue’, ‘Devinely Blue’, and ‘Feelin Blue’, fit today’s smaller garden space better than most tree forms of deodara cedar that typically reach 70-80 feet in height. All three sport lovely soft blue-green foliage.

Deodara grows best in full sun to light shade in moist fertile, well-drained soil. Deodara needs good air movement to prevent problems with needle diseases. New deodaras require regular watering during summer dry spells. All three cultivars make great accent plants among large boulders, other dwarf conifers, and rockery plants.

‘Glacier Blue’ grows 5-8 feet tall in ten years. Growth rate is moderate with a spreading to slightly pendulous arching form.

‘Devinely Blue’ grows only 3-6 inches annually. It matures into a 6 feet tall and 3 feet wide shrub. New spring foliage starts out gray-green and turns bluish green.

‘Feelin Blue’ exhibits a prostrate growth form similar to ground cover junipers. At maturity it reaches 3-4 feet in height and 6-8 feet in spread.

Winter Care of House Plants

Posted by Hugh on January 10th, 2011

: Lovely Foliage Plants at Grove Park Inn in Asheville, NC

Most plants adapt to winter’s shorter daylength and low light intensity. Interior plants require less water and nutrients. Plants also adapt to the lower room humidity in our modern day homes. Grouping plants together and spritzing them 1-2 times a day is helpful.

Soil moisture needs varies with the type of plants and the kind of containers (plastic, clay or ceramic). How long has the plant been in the same pot or planter? Plastic and ceramic pots retain soil moisture longer than clay pots.

I urge gardeners to adopt a simplistic house plant care approach. Fit plants on your everyday schedule. Make watering part of the Saturday morning chores or after Sunday church services or prior to Sunday game kickoff. Water 1-2 times weekly. If some plants don’t need water, skip them.

As winter wanes, tackle the job of re-potting those plants that have not been re-potted in one year. Gently shake off some old potting mix and transplant into a slightly larger container and new soil-less media.

Beginning March 1st, feed plants every 2-3 weeks. Most branded “house plant” fertilizers work well. My personal tip is to decrease recommended label amounts by half, and fertilizie plants twice as often from March through October.

Be vigilant about bugs and diseases. Simply washing the foliage with a mild dish washing soap, insecticidal soap or miscible oils can clean off most pest problems. Frequently, pest problems can be resolved without using inorganic pesticides.

Winter King Hawthorn – A Winter Fruit Attraction

Posted by Hugh on January 7th, 2011

: bright red fruit in winter season

‘Winter King’ is an outstanding cultivar of our native green hawthorn (Crataegus viridis) and is at home here in the Southern Appalachian region (USDA zones 6 and 7). Over the winter season few deciduous trees present a colorful fruiting display much better than Winter King.

Winter King hawthorn is a small landscape tree, maturing to 25-30 feet tall and wide in twenty years. Its medium green glossy leaves are small in size and are rarely disfigured by disease and insect problems when planted in the right landscape environment.

Winter Green grows best in a well-drained loamy soil and in full sunlight. Autumn foliage does not stand out, turning yellowish green before falling. A 3- year or older tree is exceptionally summer heat and drought tolerant.

Winter King flowers in mid-spring, usually right after ornamental crabapples, which novice gardeners often confuse with hawthorns. Individual flowers are 5-petaled and tend to be malodorous. The silvery green branches bear sparse numbers of one inch long thorns.

Winter King bears a bountiful annual crop of 1/2 inch diameter green fruits which turn bright red in the fall. They serve as a plentiful food source for winter-feeding birds and other wildlife. Deer rarely feed on the prickly branches.

As the tree ages, bark on central trunk and major scaffold branches chips off in small pieces exposing a tan to orange inner wood.