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

Fall Color in U.S. Native Azaleas

Posted by Hugh on October 4th, 2011

R. vaseyi fall color

Finally, Americans are paying closer attention to our wonderful native plants. In the Southern Appalachian region, there are 16 and more species of deciduous azaleas which may be grown here. In addition, there are numerous natural hybrids growing in the mountains.

I asked Jay Jackson, owner of Appalchian Native Plants, Inc. in Laurel Bloomery, TN which deciduous azaleas offer the best fall color. He rated these six as the best:

Pinkshell azalea (R. vaseyi)
Sweet or smooth azalea (R.arborescens)
Swamp azalea (R.viscosum)
Natural hybrids of (R. arborescens) x (R. cumberlandense)
Cumberland or bakeri (R. cumberlandense)
Flame azalea (R. calendulaceum)

The species rating order may change from year to year with the weather conditions prior to fall foliage color-up.

Plant Autumn Asters Instead Of Mums

Posted by Hugh on October 2nd, 2011

Aster 'October Skies' (photo courtesy of NorthCreek Nurseries, Landenburg, PA)

Aromatic asters (Aster oblongifolius) is one of our finest late blooming native asters for the autumn garden in the Southern Appalachian region (USDA zones 6 and 7). Through the spring and summer months, the dense gray-green shrubby foliage mounds grow 15-18 inches high and 24-30 inches wide. Hundreds of yellow-centered, daisy type flowers cover the plants. Blooms average 1 1/4 inches in diameter. The foliage emits a minty fragrance when crushed.

The botanical nomenclature of aromatic asters was recently changed to Symphyotrichum oblongifolium. The two most popular cultivars are ‘October Skies’ with bluish ray flowers and ‘Raydon’s Favorite’, a sister seedling, with blue-lavender ray flowers. Both cultivars work well as part of a border or meadow planting, or in containers. Like most asters, flowers attract numerous butterflies and are excellent cut for a table arrangement.

Aromatic asters grow in an average soil and in full sun. In gardens asters benefit from additions of compost and fertilizer to the garden soil. Established asters are very drought tolerant. Immediately after flowering, deadhead plants to reduce seed formation which may lead wild seedlings germinating in your garden in subsequent years. Using a sharp knife, split apart and tranplant emerging mounds of young shoots in early spring.

Aster yellows is a virus disease and their mortal “Achilees’ heel”. The yellow virus is spread by sap feeding insects such as leafhoppers and aphids in spring and early summer. Prevention is your only option, using contact-type insecticides. Aromatic asters demonstrate better than average deer resistance if populations are not exceptionally high.

‘Little Lemon’ Goldenrod Acts Like Late Summer Bedding Plant

Posted by Hugh on September 29th, 2011

'Little Lemon' goldenrod (photo courtesy of North Creek Nurseries, Landenburg, PA)

Across the Southern Appalachian region (USDA zones 6 and 7), the native goldenrods (Solidago spp.) are easy to spot, growing 6-8 feet tall in ditch banks along roadsides and in the poorest of soils. Over the past quarter century short, more compact cultivars have arrived local garden centers.

‘Little Lemon’ grows only 12-15 inches tall with a 18-24 inch spread. This diminutive beauty is exceptionally compact with joyous light yellow flowers opening in late summer and blooming well into the fall season. ‘Little Lemon’ combines well with other autumnal pleasures such as asters, kales, and fall anemones either in garden beds or containers.

Goldenrods prefer moist, well-drained soils in full sun or partial shade, and are tolerant of wet sites. Plants possess good heat and drought tolerances. Fertilizing goldenrod is rarely needed, but likely will enhance plant vigor.

Goldenrods do not cause hay fever in the fall. The sticky oily goldenrod pollen is to heavy to be carried in the wind. Cut goldenrod flowers are long-lasting and used in dried arrangements.

Clumps need to be divided every 3-4 years. Birds and butterflies frequent flowers often and deer don’t graze on them.

October Starts Out With Fall Sunflowers

Posted by Hugh on September 26th, 2011

Helianthus spp. at Knoxville, TN Garden Center

I thank the person who gave me a native swamp sunflower (Helianthus angustifolia). This long-lived perennial appears to have its own internal clock for blooming around the first day of October. Its long narrow rough-textured leaves average 6 inches in length. The 2-3 inch wide flowers appear first on top of the tall 6 to 7 foot plants, and numerous floral side branches soon follow.

Fall sunflowers are best grown in full sun to insure shorter sturdier plants which need no staking. Plants growing in partially shaded sites do not branch well and produce fewer flowers. If you have no room for 6-10 foot plants, cut them back by half once or twice before the mid- August. Pruning improves branching.

Swamp sunflowers are abit hoggish when it comes to soil moisture. Established plants possess moderate drought and great heat tolerances. Do not fertilize fall sunflowers as they are voracious feeders and tend to need staking, a chore I like to avoid.

In ten years plants have never become invasive in my garden. I suspect the late flowers have not enough time to mature viable seeds. Two other fall sunflowers to select for your fall garden are 18- inch tall ‘Lowdown’ willowleaf (H. salicifolius ‘Lowdown’) and 6-8 foot tall Helianthus x ‘Lemon Lady’.

Helianthus spp. are winter hardy in the Southern Appalachian region (USDA zones 6 and 7). Plant fall sunflowers from March thru July so that plant roots have adequate time to become well anchored and survive the winter cold.

Franklinia Will Survive If…

Posted by Hugh on September 22nd, 2011

Franklinia at NC Arboretum in Asheville

Franklinia (Franklinia altamaha) is admittedly a very finicky large shrub or small tree. Pure white, five-petal, 2 ½ – 3 inch camellia-like flowers bloom sporadically from August thru mid-October. Flowers are slightly fragrant. In the fall glossy green leaves gradually transition to blends of red, orange and burgundy hues.

Franklinia grows best on an eastern exposure site with full morning sunlight and sheltered from strong afternoon sun. Franklinia has a fibrous root system, preferring soil conditions similar to azaleas and rhododendrons. If growing rhododendrons are a challenge, stay away from franklinia. Soil must be compost-rich, excellently drained, and moderately acidic.

Franklinia was named to honor Benjamin Franklin. Originally discovered growing in southeastern Georgia (USDA zone 8), franklinia grows surprisingly well in our cooler Southern Appalachian region (USDA zones 6 and 7). The species is extinct in the wild, but readily available from internet nursery commerce.

Fertilize in early spring with an acidic based soluble fertilizer such as Miracle Gro®, Miracid®, or Hollytone®. Franklinia also favors an annual feeding of Epsom salts (magnesium sulfate) @ 1 Tablespoon per gallon of water per tree. Applying limestone or gypsum anywhere around the feeder roots of franklinia is highly discouraged.

Ornamental Peppers Sizzle In Autumn

Posted by Hugh on September 19th, 2011

Ornamental Peppers in mid-September Garden

Some gardeners call them “Christmas peppers”. In the late summer garden all eyes turn away from most flowering annuals and to the colorful fruits of ornamental peppers (Capsicum annuum). Many are dwarf red hot chili peppers. (No!…not the rock band).

Fruits are cylindrical or ball shaped and the brilliant colors range from white, yellow, orange, red and purple (some almost black). Plant foliage may be green, purple, or variegated. Over the years many varieties have been introduced. A popular favorite here in Tennessee, Virginia, and North Carolina is ‘Black Pearl’.

Ornamental peppers are compact growers, 12 -15 inches in height and width. They are planted either in the front of a garden bed or in containers mixed-in among other flowering annuals. Plants display fruits at their spectacular best from late August and thru frost.

Grow ornamental peppers in a sunny garden spot in fertile soils and irrigate plants during long dry spells. Do not over-fertilize (particularly nitrogen) as peppers will produce lots of leaves and few peppers. Disease and insect pests are rarely seen.

Their colorful fruits and foliage make great additions to indoor floral arrangements. Potted plants loaded with showy fruits may also be purchased from Halloween through the winter holiday season. Fruits exhibit a long display life lasting 6-8 weeks.

Caution: keep away from children or pets as the fruit are extremely hot for eating.

Fall Is For Planting

Posted by Hugh on September 15th, 2011

Gardening is part of Outdoor Living

Does your garden need a refresh? Summer’s heat and drought, devastating storms, and disease and pest problems combine to place a pall over your outdoor living space. Perhaps, you desire an entirely new look. Maybe you’re tired of the same old beds of roses, daylilies and other perennials. Maybe your garden saps too much of your time and you seek some low maintenance ideas.

Autumn is a good time to visit a full-service garden center where year- end plant bargains abound. Your first visit should primarily be fact-finding. Do not load up on new plants, but seek out new ideas and solutions. Check out patio furnishings, grills, stonework, or maybe exterior lighting in key areas of your garden.

Shade trees and shrubbery are on sale at 30-50% off, although selection, compared to their spring inventory, is more limited. Spring flowering bulbs are on sale. Bulbs like daffodils, camassias, and crocuses offer many years of floral spring beauty. Tulips and hyacinths are not long-lasting, although 3-4 years is not bad. Mix in bulbs with winter/spring blooming pansies and violas for almost 7-8 months of floral color.

Pinks (Dianthus spp.) are planted in late summer and early fall to take advantage of soil warmth. Plants grow out their rootsystems before winter sets in.

Reminder: guaranteed success with winter blooming pansies and violas sets October 15^thas the key planting deadline. If planted later in the fall, these cold tolerant annuals survive, but their winter flowering is alot less.

Steps in Re-Blooming Last Year’s Poinsettia

Posted by Hugh on September 12th, 2011

'White Winter Rose' poinsettia

Part IV. In mid-September bring plant indoors as outdoor temps start to drop below 50°F to initiate poinsettia flowering. Poinsettia is a “photoperiodic” plant, which means that floral buds and colorful bracts are initiated under short daylengths. A poinsettia requires 6 weeks of 10 hours or less of light per day.

You must be determined to stay with the photoperiodic schedule every day. Exposing a plant to just 1-2 hours more light on any day will keep the plant growing with no flower/bract response.

An alternative way of stating: keep your plant in complete darkness from 5 pm to 7 am for 40 days (6 weeks). Any momentary exposure to light will delay the bloom response. Move into a cardboard box or closet at dusk to block out the room light. Make certain that no direct light seeps in through the cracks.

By mid-November the upper leaves (bracts) should begin to color and flower buds form. Grow the plant at a sunny window and continue to water and fertilize.

Stop fertilizing around mid-December. Continue watering and enjoy your personally grown poinsettia over the holiday season.

Previous Blogs about Care of Poinsettias (dated: Dec. 18, 2010, Dec. 20, 2010, and Jan. 27, 2011)

Re-Bloomers Need Your Help

Posted by Hugh on September 10th, 2011

Encore 'Autumn Carnation' Late Summer Bloom

Re-blooming is an unusual plant trait. Selected cultivars return this time of year for a repeat floral show. In my garden Encore™ azaleas (Rhododendron spp.), re-blooming irises (Iris spp.), and re-blooming daylilies (Hemerocallis spp.) are back for second round of flowering in late summer and early fall.

The gardener/landscaper must supply needed soil moisture and nutrition (primarily nitrogen) so that plants don’t struggle through a stressful summer season. Plants become recharged by frequent irrigation and adequate feeding. In certain situations you may need to monitor and treat a disease and insect problem.

As plants finish blooming in their prime season, remove all spent flower heads to avoid seed formation. For iris prune off old flowers in late May, for daylilies in late June or early July. Encore azaleas bloom in mid-April thru early May and require no deadheading. Timing may vary according to where you garden in the Southern Appalachian region (USDA zones 6 and 7).

In addition, many perennials re-bloom a second and third time after spent flowers are removed and plants are re-nourished. Some easy to grow re-bloomers include: blanket flowers (Gaillardia x grandiflora), perennial salvia (Salvia x nemorosa), tickseed (Coreopsis verticillata), summer phlox (Phlox paniculata), Shasta daisy (Leucanthemum x superbum) and veronica (Veronica spp.).

‘Chocolate’ White Snakeroot Is A Better Choice

Posted by Hugh on September 7th, 2011

Summer foliage (photo courtesy of North Creek Nurseries, Landenburg, PA)

White Snakeroot (Eupatorium rugosum) is native to moist woodland areas in most eastern and midwestern states (U.S.). It grows in average, moist, well-drained soil in full sun to light shade. It is a long-lived and an aggressive perennial. ‘Chocolate’ (E. rugosum ‘Chocolate’) earns its namesake for its chocolaty or burgundy tinted foliage.

‘Chocolate’ white snakeroot grows to a large, shrubby mound with dark bronze leaves and white cottony flowers in early to mid-September. The darkly tinted 4-7 inch long lance-shaped leaves lose most of their chocolaty richness by late summer. The white flower clusters average 6 inches in diameter. Inflorescence sits atop shiny dark purple stems which rise 3-5 feet in height and 1-3 feet in spread.

White snake root spreads by both vigorous rhizomes and reseeding. Deadheading of spent flowers is a must to avoid self-seeding. Self-seeding gives snake root license to become an aggressive garden thug. ‘Chocolate’ does not come true from seed (returns to its wild form).

No serious insect or disease problems. White snakeroot attracts multitudes of butterflies and bees. Flowers are an important source of nectar for transitory butterflies in late summer. White snakeroot should never be planted within reach of milking cows. A poisonous substance in white snakeroot can cause a deathly human milk sickness.

Plant Chocolate white snakeroot where it may be viewed from several angles in border plantings or in naturalized areas.