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

Pest Alert – Gardeners Should Avoid Planting Garden Impatiens

Posted by Hugh on May 23rd, 2013

Bed of New Guinea Impatiens (in foreground)

Downy mildew in impatiens (Plasmopara obducens) infects garden impatiens, double impatiens and balsam. However, New Guinea impatiens, SunPatiens™, and most annual summer flowering plants are not susceptible. Impatiens are the favorite flowering annual used in shady garden areas. Double impatiens and balsam are favorites in hanging pots and other types of containers.

U.S. greenhouse growers continue to be vigilant when outbreaks of downy mildew are spotted. All diseased plants are disposed immediately and not sold to consumers. Mistakenly, healthy looking impatiens may be shipped that have been contaminated with the microscopic “oospores” which cause the disease. The plants do not show visible symptoms at time of shipping. Contamination of the garden soil with the long-lived downy mildew oospores may become a serious problem in the years ahead.

Early symptoms of diseased impatiens may appear as yellowed or off-colored leaves with a white mildew coating the foliage underside. Eventually, most leaves turn yellow and fall off, leaving only the stems.

Infected plants in the garden can not be saved by spraying a fungicide. Greenhouse growers and professional landscapers have downy mildew fungicides available to them, but these products are not available to home gardeners. Your best planting alternatives in shady garden areas are New Guinea impatiens, SunPatiens, shade coleus, and torenias.

A remedy for impatiens downy mildew disease will be found. Right now, do your part by not spreading this problem.

Garden Impatiens in shade garden

• Special thanks to Dr. Alan Windham, Extension Plant pathologist, University of Tennessee Plant and Soil Diagnostic Lab, Nashville, TN.

Pest Alert- Protect Young Trees and Shrubs From Cicadas

Posted by Hugh on May 20th, 2013

Adult cicada (photo courtesy of Dr. Frank Hale, Univ. of Tennessee Entomologist, Nashville, TN)

No insect creates more newspaper headlines than the periodical cicada (Magicicada spp.). Their sudden emergence, every 13 or 17 years reads like a chapter from a science fiction novel. Their high-pitched noise or “mating call” fills the late spring air.

Both the 13-year and 17-year cicadas are uniquely common in the eastern U.S., found no other place on Earth. The two populations, called “broods”, emerge at different times, that is, 13- or 17-year intervals depending on the locale.

Early American colonists thought they were a “locust plague”. People often confuse cicadas and locusts. A locust is actually a species of grasshoppers and feeds on foliage. An adult cicada does not feed on foliage, but feeds on twig sap. The female cicada makes injurious slits in twigs and limbs of trees to deposit eggs.

The adult periodical cicada is 1 to 1½ inches long (photo). The body is black, while the legs, eyes and wing veins which are reddish-orange. Large numbers of adults emerge in May or June when the soil temperature 4 inches deep reaches 67° F. Four or five days after emergence, the males start their high-pitched mating call to attract females. Mating occurs and females begin laying eggs.

The female cicada has a knife-like ovipositor that she uses to slit twigs of woody plants. Apple, pear, dogwood, oak and hickory are among their favorite host plants. In each slit, the female lays 24 to 28 eggs. Each female can lay a total of 400 to 600 eggs. Pencil thickness wood is the main target. Young trees are very susceptible to severe injury.

Preventative measures should be in place to protect young trees and shrubs. Pruning should be delayed until after cicada emergence so damaged branches can be removed. Cover small woody landscape and fruit trees with cheesecloth or spun row cover for protection while cicadas are present. Insecticide spraying are not an effective option.

* Special thank you to Dr. Frank Hale, Univ. of Tennessee Entomologist for providing information on cicada life cycle.

‘Florida Sunshine’ Anise Tree

Posted by Hugh on May 18th, 2013

Florida Sunshine anise tree (Illicium parviflorum

Illicium 'Florida Sunshine' at Milliken Arboretum in Spartanburg, SC in October

‘Florida Sunshine’), aka Ocala yellow star, is a southeast U.S. native which grows well on moderately shaded sites. Its evergreen, chartreuse colored, spring-summer foliage turns golden yellow in the fall. As its common name hints, the evergreen foliage emits a licorice scent.

The overall fall-winter show is nothing short of spectacular in a dull winter landscape. Leaf petioles and stems turn scarlet-red in the fall. Its ½ inch diameter creamy white flowers are easily missed in late spring.

Florida Sunshine grows vigorously into a dense shrub, 6 to 8 feet tall and slightly less in spread. Winter shade is advised to prevent leaf burning. Moist soils hasten annual growth rate. One year-established shrubs demonstrate better than average drought tolerance. Disease and pest problems and resistance to deer feeding have been reported, although additional reports need to be gathered.

Foliage may scorch in direct sun on exposed wintry sites in zone 6 areas. At the Milliken Arboretum in Spartanburg, SC (zone 7), Florida Sunshine is planted out on an open site with irrigation.

Make Florida Sunshine a bright focal point in your garden. It is a good choice for partly shaded woodland settings or in foundation plantings, or as a low – growing evergreen hedge. In containers its golden accent should be mixed with other colored foliage plants. Tender roots in containers should be protected over the frigid winter months.

Florida Sunshine was introduced by Tony Avent, owner of Plant Delights Nursery in Raleigh, N.C.

‘Bikini-tini’ Colocasia Creates Movement in The Garden

Posted by Hugh on May 15th, 2013

Cupped Leaves of Bikini-Tini Colocasia

Colocasia (Colocasia esculenta), aka taro, ape plant, and elephant ear, among other names, is marginally hardy in the Southern Appalachian region (USDA hardiness zones 6 and 7). The 2011 colocasia introduction ‘Bikini-tini’ has garnered high praise from neighbors and friends visiting my garden in the summer.

Bikini-tini is a strong stemmed thick-leaved plant that grows 4 to 5 feet in height. Its bluish-gray leaves cup upward, supported by dark purple petioles and prominent veins beneath. Its cupped leaves capture and pour out rainwater, creating motion in the garden.

Elephant ears are easy to grow. Your garden or container soil should be well drained and compost rich. Soil pH should range between 5.6 and 7.0. Site in direct sunlight, and keep the soil moderately moist. Elephant ears are heavy feeders and thrive on a steady diet of water plus fertilizer. Use a water soluble product such as Miracle-Gro®, Jack’s Classic®, or Daniels® every 2-3 weeks from mid-May (planting time) to late August at the one-half strength rate. An alternative is to feed once with an organic slow release fertilizer in early spring.

Disease and pest problems are rare when plant(s) are properly sited and cared for. Potential crown or stem rot problems are best avoided by growing in a well drained soil (media) and by not overwatering.

Bikini-tini is rated winter hardy to USDA zone 6 with some protection. Protect the crown over the winter with 2-3 inches of a loose leafy mulch such as straw or oak leaves.

Australian Fanflower A Hot Choice in U.S. Southern Gardens

Posted by Hugh on May 12th, 2013

Scaevola (pink variety)

Fanflower (Scaevola aemula) is a relatively new annual bedding plant choice. This Australian native thrives in tough environmental conditions, including the hot, humid summers in the Southern U.S.

Fanflower grows well in hanging baskets, containers or garden beds. It grows in average, moderately acidic, well-drained soil and prefers full or partial sunny areas in the garden.

Non-stop powder blue flowers arise in the leaf axils on trailing stems. Once established, tough hardy fanflowers are only stopped by a heavy frost in late fall in the Southern Appalachian region (USDA hardiness zones 6 and 7). The medium green, oval-shaped toothed leaves average 2-inches in length.

Exhibiting a trailing growth habit, fanflowers grow vigorously, 6 to 9 inches tall and spreading up to 24 inches wide along with adequate summer moisture and nutrition. Some taller forms are available. Fanflower has no serious insect or disease problems.

Typical blue fan-shaped summer flowers give the plant its name. The Surdiva® series features 3 colors: blue, light blue, and white. They make ideal edging plants in containers or garden beds mixed with other annuals and perennials. The Bombay® series includes a pink flowering form, ‘Bombay Pink’.

'Surdiva White' Scaevola

Floral Fragrance Of Native Fringetree Fills The Spring Air

Posted by Hugh on May 10th, 2013

Native Fringetree Flowering in East Tennessee in mid-May

Fringetree (Chionanthus virginicus) is treasured for its billowy masses of fragrant white flowers in the spring. It commonly grows as a large 15-20 foot tall shrub, but can be easily trained into a 20-25 foot multi-stemmed small tree.

Most gardeners call this native “fringe tree” or fringetree. Regionally, it goes by a number of colloquial names, including “grancy graybeard” (or grandpa’s graybeard) and “flowering ash”. The latter name refers to its close kinship with ash trees (Fraxinus spp.) and lilacs (Syringa spp.) which belong to the same plant family Oleaceae.

Fringetree blooms for nearly 3 weeks, from May into early June in the Southern Appalachian region (USDA hardiness zones 6 and 7). White fragrant flowers spring forth, just days ahead of its large bold textured foliage. The dark green leaves are 3 to 8 inches long and 3 to 4 inches wide, and remain blemish free all summer long.

Most fringetrees are seed propagated which leads to wide variation in fall color. Fall color can be an exceptional bright yellow in some years on particular plants. Others nearby may finish a plain yellowish green color before abcising.

Fringetree is dioecious, meaning flowers are mostly either male or female on the plant. Male flowering trees are said to produce larger showier flowers. The cultivar ‘Emerald’ is a male grafted clone. Female fringetrees bear powder blue fruits in late August. The seeds inside the fruits require 2 years to germinate. It is rare to find lots of seedlings growing in the wild.

Tight clay soils should be avoided and optimal growth occurs in slightly acidic soils. Fringetree grows best in full sunlight with plentiful flowers. In partial shade, the shrub gets tall and leggy, and produces fewer flowers.

‘Thailand Giant’ Elephant Ears A Tropical Wonder

Posted by Hugh on May 7th, 2013

Enormous Leaves of Thailand Giant (photo courtesy of Plant Delights Nursery)

In many areas of the U.S.’Thailand Giant’ elephant ears (Colocasia gigantea) is classified as an annual (USDA hardiness zone 8-10). It grows best in full to partial sunlight (6-hours minimum) and planted in a compost-rich well-drained garden soil or good container potting media. A young plant should be moved outdoors and brought back indoors when night temps fall below 40°F. Thailand Giant may be permanently moved outdoors when night temps are above 45°F.

Thailand Giant grows into a massive 8 to 9 foot tall plant with shiny grayish green foliage. In the garden individual leaves grow in excess of 4 to 5 feet in length and 3 to 4 feet wide if luxuriantly watered and fertilized. Feed with a water-soluble fertilizer such as Miracle-Gro™ or Daniels™ Plant Food, applied bi-monthly from spring planting time until September 1.

Clusters of large fragrant white flowers form at an early age, but are mostly hidden among the enormous sized leaves. The gigantic,tropical looking leaves is the major reason for growing Thailand Giant. Keep the garden soil moist, but not sopping wet. During hot dry summer periods, it should be watered frequently, as much as 2 inches per week.

A few days before first autumn frost, cut back the foliage, dig up the plant, and transplant into a large wide-based container. Store in a cool place (40-45 °F) over the winter and keep soil (potting media) relatively dry. The crown should remain dormant until watering starts up growth in early spring.

Chenille Plant Hot For The Summer Garden

Posted by Hugh on May 4th, 2013

Chenille plant (Acalypha) at Dallas Arboretum)

Chenille plant (Acalypha hispida), aka firetails and redhot cattail, is a hot tropical plant which has jumped from house plant to garden plant use. Their pendulous vibrant red (other colors are available) tassel-like flowers mimic the furry tails of pets. Its lush dark green foliage is heart-shaped. Stems arch downward under the weight of the enormous catkin flowers which may be 4-10 inches in length. In a public garden it is common to watch children walk up and touch them.

Under ideal moisture and tropical warmth, chenille may grow to 8-10 feet in height with a 4 to 6 feet spread. Dwarf and trailing forms of chenille (A. pendula or A. repens or A. reptans) are available. Put these in hanging baskets or let them spill over the edge of a large container. Chenille grows to less than half their garden size in containers.

Add chenille to the middle or back of a sunny perennial border to fill in an empty spot over the summer. It starts blooming in the heat of the summer and continues through the warm days of autumn. Mix chenille with other plants with red hues, such as Red Abyssinian banana, coleus, ‘Strawberry Fields’ gomphrena, among other options.

Chenille grows vigorously. It prefers a moist, well-drained soil with adequate watering through the normally dry summer. Pruning plant(s) back by half in early July develops a compact, more floriferous habit. Occasionally remove spent flowers to keep chenille tidy.

Chenille plant may be grown as a house plant. Cuttings root easily, gathered from plants in the garden. Be vigilant not to invite garden pests indoors in the fall, an easy thing to do. Tropical chenille thrives in a warm humid room with a temperature minimum of 60 °F and full day sunlight. These environmental conditions are best found in a sun room or greenhouse.

Warning: chenille plant belongs to the Euphorbia family; its sap is mildly toxic to people and pets, and may cause eye irritation and dermatitis. Young children are particularly attracted to the bright fuzzy pendulous flowers.

Snow Fountains® Weeping Cherry Fits Small Gardens

Posted by Hugh on April 30th, 2013

Closeup of Snow Fountain Cherry Blooms

Snow Fountains® (Prunus x ‘Snofozam’) is a slow-growing, weeping ornamental cherry that grows compact. It develops into a 8 to 15 feet tall and 5 to 12 feet wide tree. This cultivar is also listed as ‘White Fountains’ in some nursery catalogs. The cascading branches flow downward or may take on a green mound form. This dimunitive weeping cherry is covered with hundreds of pure white flowers in early spring.

The small 5-petalled white flowers attract numerous butterflies and pollinating bees, along with early arriving hummingbirds. A few small black, inedible fruits may develop 4-5 weeks after bloom, and are of no ornamental value. Summer foliage is dark green, and the 3-inch and longer leaves develop autumn blends of golden or orange before falling.

Grow in a medium moist, slightly acidic, well-drained soil. Plant Snow Fountains (or any cherry cultivar) in full sun and do not overcrowded for good air circulation to insure disease free growth. Prune when necessary after spring flowering to shape and to remove diseased and pest-ridden twigs and branches. Borers and stem cankers can be significant problems when the tree is environmentally stressed.

Aphids, caterpillars, Japanese beetles, and scales continue a possible litany of pest problems. Fungal and bacterial leaf spot diseases may lead to holes in the summer foliage. Utilize appropriate pesticides as needed.

Most varieties of weeping cherries grow very tall and wide for small landscapes. Snow Fountain grows a lot more compact and is an excellent planting option for small urban sites.

‘King Tut’ Papyrus Adds Texture To The Summer Garden

Posted by Hugh on April 27th, 2013

: Standard sized Papyrus in Flower Bed at Kingwood Center in Mansfield, Ohio

Over thousands of years papyrus (Cyperus papyrus), aka Egyptian paper plant, was essential for food, medicine, fiber and shelter in ancient Egypt. Today, we utilize papyrus, as many other aquatic and bog-like plants, to add texture to the garden. Papyrus is classified as a non-hardy sedge (winter hardiness to USDA zone 9).

Invite this lovely exotic from the African continent into the summer garden or into a container on your patio or deck. It’s perfectly happy growing with its feet in water, and will prosper in garden soil under frequent drip irrigation. Papyrus grows at the edge of a water garden or ponds, in boggy soils, or in standing water in containers. Optimum growth is in full sun, but it tolerates partial shade. This incredibly fast grower will add 5 to 8 feet in a single season.

‘King Tut’ is a dwarf 4-5 feet tall cultivar. Its leafless green triangular stems stand tall and rigid at 2 to 3 feet high. Inadequate sunlight may compromise stem sturdiness. Roots are woody rhizomes which anchor the plant in a garden soil or container gravel medium. Papyrus does not suffer from serious insect or disease problems.

In the Southern Appalachian region (USDA zones 6 and 7), plants must be potted up and brought indoors before frost for winter care. Maintain at 40° F minimum temperatures and high humidity in a mostly sunny window, a sunroom, or a greenhouse.

Invite this beautiful Egyptian water plant into your garden. Garden centers often sell papyrus in their aquatic supply department or purchase from an e-commerce nursery on-line.