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

Heat Tolerant Annuals That Create Their Own Heat

Posted by Hugh on July 18th, 2013

Plant Wagon on Savannah, GA Street in Early July

In some parts of the U.S. summer is sizzling, and it may also be very dry. Several colorful annuals cope with summer heat and humidity better than others. Northeast U.S. cities are sweltering near 100°F.

A sure bet is that every summer will be hot and humid in Savannah, GA. Near a popular restaurant is a the wagon (photo) planted with a mix of sun-loving coleus, fanflower (scaevola), Egyptian star flowers (pentas), and cupheas. All are thriving.

Many other annuals can handle Southern heat and humidity. The following list is not complete: summer snapdragons (angelonia), moss rose (portulaca), celosia, salvia, lantana, marigold, star zinnia (Zinnia angustifolia), wax begonias, Globe amaranth (gomphrena), and periwinkles (vinca). Non-flowering annuals grown for lovely colorful foliage include sweet potato vine, coleus, canna, amaranthus, Caricature plant (Graptophyllum pictum), acalypha (Acalypha spp.), and variegated tapioca plant (Manihot esculenta ‘Variegata’).

It’s best to plant and establish annuals 5-6 weeks prior to the arrival of high heat and humidity. Flower beds should be properly mulched to conserve water loss. Plants in large containers may need to be watered daily or every other day during summer dry spells. Fertilize at planting time and in mid-summer with a water-soluble fertilizer products such as Miracle-Gro™, Jack’s™, or Daniels™.

Long Blooming Colorful ‘Kaleidoscope’ Flowering Abelia

Posted by Hugh on July 15th, 2013

'Kaleidoscope' abelia as compact shrub in Asheville, NC

Abelia (Abelia x grandiflora) is a popular shrub in the Southeastern U.S. (USDA hardiness zones 6–9). Foliage is evergreen in USDA Zone 7 and south. The cultivar ‘Kaleidoscope’ is a form of abelia that can be utilized as a 2 to 3 feet tall by 3 to 4 feet wide compact shrub or low spreading ground cover.

Kaleidoscope is best remembered for its seasonal foliage color bursts. In the spring lemon-yellow variegated leaves, with lime green centers, grow from reddish stems. Summer foliage develops a golden hue, then morphing into blends of reds, oranges, greens and yellows in the fall. The vividly colored variegated foliage does not burn in the heat of summer.

Pale pink floral buds open to white tubular flowers and bloom from early summer (July) into fall (October). Blooms tend to blend with the lightly colored leaves. Butterflies and many other pollinating insects are attracted to this easy to grow shrub
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Abelias require little maintenance other than removal of aberrant leaders (suckers) which spring up in early summer. Prune off suckers if a uniform shrub or ground cover height is desired. Abelias thrive in full sun (6-hours minimum) and are planted in a well-drained soil.
Feed abelias with 10-10-10 or equivalent granular fertilizer in late winter or spring. Water-soluble fertilizer (such as Miracle-Gro®, Schultz®, Jacks® or Daniels®) is applied 3 times from early spring to mid-August.

Troubled Pines… And Some Good Ones To Grow

Posted by Hugh on July 12th, 2013

Scots Pine at Kingwood Center in Mansfield, Ohio

Mugho, aka mugo pine (Pinus mugo), and Scots pine (P. sylvestris) are two troubled pines which gardeners in the Southern Appalachian region (USDA Hardiness zones 6 and 7) have shied away from planting. Both have become problem growers over the past quarter century. Scots pine suffers from several devastating foliar diseases. Once a popular Christmas tree, it is no longer grown.

Mugo pines have problems with poor soil drainage, phytophthora root rot and Cylindrocladium root rot. Newly planted mugos generally live 3-5 years before they start to decline due to root weevils and other root-related diseases.

Cyclaneusma needle cast is the devastating disease of Scots pine in the mid-South region of the U.S. Diplodia tip blight has also been a problem. Often, latent infections of Diplodia don’t show up for several years. Scots pine is no longer grown as a Christmas tree; fraser fir (Abies fraseri) and white pine (P. strobus) have replaced Scots pine in the Christmas tree marketplace.

Fortunately, many pines, including the ubiquitous white pine, perform well in the region. Some favorites in my east Tennessee garden (zone 6-b) include: lacebark pine (P. bungeana), several forms of Japanese red pine (P. densiflora), including cultivars ‘Jane Kluis’ and dragon-eye ‘Oculis Draconis’, Bergman Japanese white Pine (P. parviflora ‘Bergman’), and Vanderwolf Pyramid limber pine (P. flexilis ‘Vanderwolf Pyramid’).

Source: Special thanks to Dr. Alan Windham, University of Tennessee Plant Pathologist, Nashville, TN.

Silver Linden Foliage Shimmers On A Windy Day

Posted by Hugh on July 8th, 2013

Mature Silver Linden at Kingwood Center, Mansfield, Ohio

Silver linden (Tilia tomentosa) is a rarely planted large shade tree. Native to southeastern European, silver linden demonstrates better heat and drought tolerances in the southern U.S. than most lindens. It grows to 50 to 60 feet in height over 25-30 years with a moderate annual growth rate. A newly planted tree exhibits a narrow pyramidal form, but begins to develop a rounded spreading canopy after 10-12 years.

Summer foliage is dark green but the leaf underside and petioles are covered with a soft white hairy pubescence. On the breezy day, the fluttering silvery leaves shimmer. Dust particles tend to build up within the leaf hairs and dull the shimmer. Autumn foliage turns yellow in the fall before dropping. Its smooth gray trunk on a young tree is similar to beech (Fagus spp.).

Single-winged fragrant flowers appear in mid-June, and the “whirligig” seeds follow 5-6 weeks later. Compared to other linden species, silver linden is rarely troubled by disease or insect pests. Japanese beetles and aphids plague other linden species, but not silver linden.

Silver linden is best planted in a compost-rich, well-drained soil with a pH between 6.2 and 7.0. A two-year established tree is very heat and drought tolerant. Pruning needs are minimal, such as removing low-lying branches and root suckers.

Silver linden cultivars, Green Mountain® and ‘Sterling’, are similar with a broad pyramidal branching habit and a more silvery leaf undersides.

Silvery leaf underside of Tilia tomentosa

Pest Alert: Spotted Wing Drosophila Attack Blueberry and Cane Fruits

Posted by Hugh on July 5th, 2013

Spotted wing drosophila (SWD) male

Spotted wing drosophila (SWD), Drosophila suzukii, is an invasive and destructive pest originating from eastern Asia. It is a pest that can not be managed with pesticides alone. Caneberries such as raspberry and blackberry appear to be most affected followed by strawberries and blueberries. Among the tree fruits, cherries seem to suffer heavy damage.

If SWD is found, home gardeners should wash fruits thoroughly. For clean fruits commercial growers should harvest and destroy all ripe and ripening fruits when SWD is found. Follow-up with weekly (sometimes bi-weekly) spraying with organo-phosphate and pyrethroid classes of pesticides. Wet weather conditions and poor sanitation practices after fruit harvest worsen SWD attacks. Hot and dry weather lessens fruit injury.

Good sanitation is as important as pesticide spraying to prevent future infestations. Eliminate all fruits that have fallen to the ground and all infested fruits remaining on the plants to reduce SWD populations that might infest later ripening fruits or next year’s crop.

SWD can develop large populations, 10-12 generations per growing season in the mid-Atlantic and Southern Appalachian regions (USDA hardiness zones 5-8). It overwinters as adults and is active in early spring. They are most active when highs are between 62° to 83ºF, humid conditions, and fruits are present. The SWD can complete one generation in a short 12 to 14 days.

The adult SWD looks like many other Drosophila species, including the common vinegar flies that infest rotting fruit. SWD attacks the fruits in all stages- undamaged, ripe or unripe. SWD adults are small flies (size: 1/10 inch) with red eyes and a pale brown body with black stripes on their abdomen. Adult males have a distinctive black spot near the tip of each wing. Females do not have these spots. The immatures of the SWD are very small white maggots.

Special Thanks to: Dr. Frank Hale, Extension Entomologist, University of Tennessee, Nashville, TN

Pest Alert: Brown Marmorated Stink Bug

Posted by Hugh on July 2nd, 2013

BMSB on okra (photo from Dr. Frank Hale, Extension Entomologist, University of Tennessee, Nashville)

In recent years Brown Marmorated Stink Bug (Halyomorpha halys), aka BMSB, has become serious pests of fruits, vegetables, and farm crops in the Mid-Atlantic and Southern Appalachian regions. BMSB are likely to spread to other areas in the U.S. They feed on all parts of plants (fruit, stems, leaves). They may also become a major nuisance invader in our homes, particularly in the fall.

BMSB are classified as a “true bug” (order-Hemiptera), native to China, Japan, and Korea. Adults are approximately 2/3-inch long and in shades of grayish brown. Their backs display the typical “shield” shape of other stink bugs. Masses of 20 to 30 eggs elliptical shaped eggs are light yellow to yellow-red, attached side-by-side to the underside of leaves.

BMSB have one generation per year in the Mid-Atlantic and Southern Appalachian regions. In a mild year, warm spring and summer conditions, count on the development of two generations. Adults will emerge in the spring, mate, and deposit eggs from May through August. The eggs hatch into small black and red nymphs that go through five molts (instars). Adults search for overwintering sites, including house walls and insulation, in late September through October.

Fruit crops include apples, peaches, plums, figs, blackberries, mulberries, citrus, and persimmons. Infested vegetables include sweet and field corn, tomatoes, lima beans, green peppers and soybeans. Some landscape plants are also damaged. BMSB scar the skin surface of apples and peaches, referred to as “cat facing,” and renders fresh fruits unmarketable.

BSMB cause no harm to humans, but the bugs enter homes as “accidental invaders” and can become an odorous nuisance. They get inside and don’t leave. They will not reproduce or cause structural indoor damage. They are best swept up in a vacuum cleaner, sometimes multiple times a week. Smashing several bugs will explain their name, as their foul smell may become quite apparent.

To keep stink bugs from entering homes and buildings, seal cracks around windows, doors, siding, et al. with silicone or latex caulk. Screens on doors and windows should be properly maintained. People may carry them indoors on the clothes.

Exterior applications of any synthetic pyrethroid insecticide in the fall may reduce insect numbers, but these products have only a short residual life. Two or three applications per week may be warranted. Insecticides should not be sprayed indoors. Read and closely follow the pesticide label.

Newly-hatched Nymphs (two instars) of BMSB on underside of dogwood leaf (photo by R. Murphy)

“Red Sells”: Red Flowering Crape Myrtles

Posted by Hugh on July 1st, 2013

Red flowering crape myrtle

In the Southern U.S. crape myrtles (Lagerstroemia spp.) provide summer long flowering. In the garden center business there is a popular saying: “red flowers sell”. Among crape myrtles red flowering cultivars generally outsell all others.

Probably the most popular red variety is Dynamite®, a Carl Whitcomb introduction. Dr. Whitcomb followed with other red introductions of different sizes – Red Rocket®, Tightwad Red® and Siren Red®. The U.S. National Arboretum released ‘Arapaho’ and ‘Cheyenne’.

When deciding which red to plant, select a variety that is the appropriate size at maturity for the site. Your choices are: dwarf types (low 3 to 4 feet), semi-dwarf types (4 to 12 feet), and intermediate shrub and tree types (12 to 30 feet in height). All listed cultivars are reliably root hardy in zone 6-b and above-ground hardy in zone 7-b.

Some cultivars strut better disease and pest resistance, magnificent fall leaf color, and awesome exfoliating winter bark.

Dwarf Red-Flowered Crape Myrtles (up to 4 feet tall)

Cherry Dazzle^® – low mounding shrub habit

Petite Red Imp™ – rounded head shrub

Tightwad Red^® – rounded shrub with dense foliage

Victor – dwarf upright branching shrub

Semi-Dwarf Red-Flowered Crape Myrtles (from 4 to 12 feet tall)

Cheyenne – 8-10 feet tall rounded head shrub

Christiana – 8-10 feet tall upright vase-shaped shrub

Siren Red^® – 10-12 feet tall upright branching shrub

Tonto – 8-10 feet tall vase-shaped shrub

Intermediate Shrub Size Red-Flowered Crape Myrtles (over 12 feet tall)

Arapaho – 20 feet tall upright branching shrub or small tree

Centennial Spirit – 10-20 feet tall stiff upright branching shrub

Dynamite^®– 10-15 feet tall stiff upright branching shrub

Red Rocket^®– 15-20 feet tall upright branching shrub.

Stop Ignoring And Start Planting Hophornbeam

Posted by Hugh on June 28th, 2013

Hophornbeam (Ostrya virginiana) in Southeast Pennsylvania

Hophornbeam (Ostrya virginiana) is a medium sized tree native to the eastern half of North America (USDA hardiness zones 4-8). The tree is practically ignored by landscape designers and installers. Few nurserymen grow it.

Hophornbeam is often confused with the true hornbeams (Carpinus spp.). Both are called “ironwood”, referring to the hard muscular wood of both genera. Ostrya averages 35 to 40 feet in height and 20 to 30 feet in width in an open location. As the tree ages, its canopy becomes more rounded.

Year-round interest can be found in its flowers, fruit, foliage, tree form, and bark. The 3-5 inch long, doubly serrated foliage is medium to dark green in summer color, and finishes yellow-brown in the autumn before falling. Hophornbeam bears distinctive male and female flowers on the same tree. Small male catkin flowers, grouped in threes, are reddish to brown in color. Male flowers are visible on the tree in winter. The greenish female flowers give way to 2 ½ to 3 inches long, drooping hops-like seed pods. Tiny nutlets inside the seed pods persist most of the winter and are an important food source for birds.

Hophornbeam grows in either sun or shade, developing a full, dense canopy in full sun and in moist, well-drained, moderately acidic soils. It tends to be slow growing at first and becomes more moderate after 2 years when properly mulched and not environmentally stressed. It is remarkably shade tolerant and, in its natural woodland habitat, develops into a small 15-20 foot open-branched tree or large shrub.

A young tree exhibits smooth, muscular trunk with slender branches which grow in a zig-zag pattern. The bark gradually ages, shedding in small thin patchy pieces, valued by some for winter interest. The tree is rarely damaged by deer.

2013 Garden Participation Up, Total Spending Still Down

Posted by Hugh on June 24th, 2013

Garden Center Shopping Aisle

The National Gardening Association recently released their 2013 National Gardening Survey. Household participation in gardening rose 2% since 2011— now totaling approximately 85 million households.

Popularity in food/edible gardening continued to rise for the sixth straight year in a row, soaring past flower gardening in terms of dollars spent. The increase in male gardeners from the 18- to 34-year old accounted for the largest spending boost.

U.S. households continue to spend more at Home Improvement Centers (27% of the total gardening retail market) and at Mass Merchants (20%) than they do at local Garden Centers and Nurseries (17%) or local Hardware Stores (15%).

This is the second year in a row that lawn and garden sales rose, after being down the previous two years. The average annual spending per household was down $4 to $347. Time and lifestyle, not the weather, seem to be more important factors determining how people spend their dollars.

Total sales of green goods are still languishing. In the battle for consumer entertainment time and dollars, the lawn and garden industry is competing against movies-on-demand, video games, watching sports, and electronics.

Source: National Gardening Association

‘Tom Thumb’ Cotoneaster Perfect For Small Spaces

Posted by Hugh on June 22nd, 2013

New Spring Growth on 'Tom Thumb' Cotoneaster

The world of cotoneasters (Cotoneaster spp.) is primarily an assortment of medium to tall growing shrubs. Cotoneaster ‘Tom Thumb’ (syn. C. ‘Little Gem’) is very different. Its diminutive size fits into those small spots such as a rock garden or among dwarf conifers. Its dark green shiny foliage creates a textural contrast with many annuals or perennials.

Slow-growing ‘Tom Thumb’ may achieve 6 to 12 inches in height and 3 to 6 feet in width over 10-12 years. It hugs the ground, and often self-roots. It may be utilized as a deciduous ground cover, although this may be expensive option. Slightly taller bearberry (C. dammeri) or cranberry (C. apiculatus) cotoneasters are cheaper ground cover alternatives.

Its tiny spring flowers are mostly inconspicuous. Fruit numbers in the fall is never plentiful and have little ornamental value. In the autumn foliage turns bronzy red and is rarely an attention grabber. (USDA hardiness zones 5–7).

A native of western China, most nursery catalogs classify Tom Thumb as a variety of C. horizontalis, but others place it with C. adpressus or C. apiculatus. ‘Tom Thumb’ thrives in full sun or partial shade, and most pests don’t seem to bother it. Tom Thumb is not fussy about soil as long as it is well-drained. This slow growing plant requires little or no pruning.

Many cotoneasters are susceptible to fire blight, a bacterial disease.