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

Sweet Potato Vines

Posted by Hugh on April 9th, 2017

Sweet Caroline ‘Light Green’ Sweet Potato Vine at NC Arboretum, Asheville, NC

Illusion ‘Midnight Lace’

Ornamental sweet potato vines (Ipomoea batatas) have been around since the late 1980’s, but their popularity have soared over the past decade. These sweet potatoes aren’t for the table. The colorful vines thrive in the intense heat of U.S. summers from May through September (zones 5-11).

These easily grown plants work well as a low-growing bedding plant, summer ground cover, weepers in hanging baskets and large containers, or vertically climb with trellis support. Older varieties, like Margarita and Blackie, were almost too vigorous and new introductions come in more color choices and grow more compact. Ornamental sweet potato cuttings will root effortlessly in water or soil.

Colorful foliage

Their colorful foliage is the big show. Ornamental sweet potatoes generally do not flower under normal garden conditions. Small, lavender, trumpet-shaped flowers may form in late summer or fall and are mostly hidden under the foliage.

Ornamental sweet potatoes do best and are most colorful in locations that receive 6 hours or more of direct sunlight. They do grow in shadier locations, but vines are not as vigorous or colorful. Average garden soil, fertility and lots of water is all they need.

Insects to watch for

Sweet potato vine is relatively carefree, there are a few problems to watch out for. Pest problems include the sweet potato looper, a caterpillar that chews holes in the leaves, and the sweet potato whitefly.

Control the looper with occasional applications of an insecticide containing BT, spinosad, a pyrethroid (permethrin, bifenthrin, cyfluthrin and others) or carbaryl (Sevin). Wwhitefly can be managed with Summer Light Oil Spray, bifenthrin (Talstar™or Malathion. Disease issues are minimal.

Newer cultivars

New cultivars display various leaf shapes, growth rates and foliage colors. Some feature shorter stem nodes between the leaves, reduced root size, and more compact habit.

Spotlight series (lime, red, black foliage) new for 2017 from Ball FloraPlant

SolarPower series (black, lime, red foliage) new 2016 from Ball FloraPlant

Sweet Caroline Sweetheart series (light green, red, purple with heart-shaped leaves)

New for 2017 -‘Sweet Caroline Sweetheart Jet Black’ and ‘Sweet Caroline Bewitched Green with Envy’

Sidekick series (black and lime with different leaf shapes) from Syngenta.

Desana series – new colors, leaf shapes and compact types.

Illusion series from Proven Winners feature thread-leaf foliage, more compact and less vigorous. Cultivars include Emerald Lace, Midnight Lace and Garnet Lace. ‘Bewitched After Midnight’ (maple-leaf-shaped, purplish-black foliage) also from Proven Winners

According to Dr. Allen Owings, these 6 cultivars grow much less aggressive:

Bewitched Green with Envy (more green)
Solar Power Lime
Spotlight Lime
Sweet Georgia Light Green
Sweet Caroline Light Green
Bright Ideas Lime

Credit: update of current varieties provided by Dr. Allen Owings, Research Horticulturist at the LSU Trial Gardens in Hammonds, LA.

Night Blooming Plants For Temperate Climates

Posted by Hugh on April 6th, 2017

Evening primrose in a late June Garden

Hemerocallis ‘Citrina’

If you are working away from home all day long, you might consider growing a few plants that bloom at night. Here’s a short list of plants whose flowers will add beauty to your evening garden:

Evening Primrose (Oenothera glazioviana) – this biennial grows 1-5 feet tall. Plant(s) are basal growing in year one and produce sturdy floral stems the second year. Bright lemon yellow 1 inch diameter blooms are 4-petalled and flower in June and July (in Tennessee). Previous evening blooms decline in late morning.

Citron Daylilies (Hemerocallis citrina) – an evening blooming daylily species whose large bright yellow blooms unfurl on tall flower scapes. Leaves are dark green and very grass-like. Flowers are also highly scented. Clumps do not require dividing for several years. Daylilies prefer full sun and moist well-drained soil.

Moonflower (Ipomoea alba) – showy night blooming vine with heart shaped leaves (annual; zones 9 – 11). Flowers are lightly fragrant; prefers full sun and moist well-drained soil.

Four O’ Clocks (Mirabilis jalapa) – popular flowering annual (zones 8 – 11). True to its name, blooms open late afternoon in full sun to partial shade; lightly fragrant flowers available in yellow, pink, purple, red and white. Plants grow 1.5 to 2.5 feet high and wide and flower from mid-summer into early fall.

Night-flowering Catchfly (Silene noctiflora) – has perfect flowers (both male and female parts), narrower petal lobes, capsules with 6 teeth, and sticky hairs. While both species bloom at night, Night-flowering Catchfly starts closing up in earlier morning while White Campion (Silene latifolia) flowers stay open until noon, and even later on cloudy days (zones 5-9).

Night Blooming Jasmine (Cestrum nocturnum) – a tropical shrub (zones 9 – 11) with non-distinctive white, star-shaped tubular flowers which are strongly fragrant, at times overpowering. Grow outdoors on a deck or patio in full sun and bring back indoors once evening temps drop below 45°F.

Night Blooming Cereus (Epiphyllum oxypetalum) – this member of the Orchid Cactus family requires a period of dryness and cool nighttime temperatures during winter to insure summer bloom. Pure white flowers, the size of a dinner plate, open soon after the sun goes down, remains open all night, and closes the following morning. Blooms are spectacular and highly fragrant. off and on through the summer months.

Night-blooming Tropical Waterlilies (Nymphaea spp.) are easily distinguished from hardy water lilies in that their leaves are serrated or jagged. Tropical lilies come in day blooming and night blooming varieties. Day blooming varieties open several hours after sunrise and close a few hours before sunset. Night blooming varieties open 1-2 hours before sunset and remain open a few hours after sunrise.

These plants are visited nightly by such pollinators as moths, butterflies, bees, bats, and occasionally hummingbirds.

Tropical waterlily (day blooming)

Late Rising Perennials

Posted by Hugh on April 3rd, 2017

Late rising Asclepias tuberosa

Hardy begonia (Begonia grandis)

As air temperatures rise in the spring, most garden perennials and wildflowers are emerging from the ground. With the sudden appearance of 80°F temperatures, many seem to blast through the still cold soil in 1-2 days, and in full bloom a few weeks later. Yet, through the month of April, some of your prized perennials show no signs of life.

A number of these tardy perennials require both warm air and soil temperatures. They’re not rarely fooled by unseasonable warm-ups. In northerly locations (USDA zones 4 and colder), some may not emerge from the soil until June.

When you first plant them, mark the spot with easy to find label so no harm comes, such as digging in the wrong spot. Follow the same practice for spring flowering bulbs such as daffodils (narcissi), tulips or hyacinths. Mark all areas where springtime wildflowers such as Virginia bluebells (Mertensia), trilliums, Jack in The Pulpit (Arisaema), bloodroot (Sanguinea), twinleaf (Jeffersonia), and many others inhabit.

Some perennials that emerge in mid- to late- spring:

Milkweeds (Asclepias spp.)

False Indigo (Baptisia spp.)

Hardy begonia (Begonia grandis)

Leadwort (Ceratostigma)

Crocosmia (Crocosmia x crocosmiiflora)

Joe Pye Weed (Eupatorium spp.)

Whirling Butterflies (Guara lindheimeri)

Perennial hibiscus (H. moscheutos)

Swamp hibiscus (H. coccineus)

Some deciduous ferns – example: Royal fern (Osmunda regalis)

Red hot poker (Kniphofia uvaria)

Russian sage (Perovskia atriplicifolia)

Balloon Flower (Platycodon)

Black eyed Susan (Rudbeckia ssp.)

Indian pink (Spigelia marilandica)

Lady’s Slipper Orchids (Cypripedium), Solomon’s Seal (Polygonatum) and False Solomon’s Seal (Smilacina) may not poke up above ground their first year after planting.

Tips On Growing Azaleas

Posted by Hugh on March 31st, 2017

'El Freda' hybrid azalea at Bellinggraph Botanical Gardens in Mobile, AL

‘El Freda’ hybrid azalea at Mobile Botanical Gardens in Mobile, AL

Red azalea in a Johnson City, TN garden

Evergreen azaleas (Rhododendron spp.) are actually small-flowered rhododendrons. Depending on where you garden, azaleas enjoy a long bloom period from late March (zone 8) to June (zone 4) in the U.S. Many cultivars bloom for two weeks or more. Fall blooming types like Encore® and Bloom-a thon® series are also available.

Azaleas have shallow root systems and most of their feeder roots are near the surface. Dig shallow wide holes in well-drained soil that are amended with lots of organic matter. Water deeply after planting. Water your newly planted azalea weekly if the weather is dry, at least for the first year.

Fertilize azaleas in the spring or fall. Use a granular, slow-release fertilizer that is acid-forming. Established azaleas often do well with no fertilizer at all. If your soil is alkaline (pH>7), add iron sulfate or ammonium sulfate to lower pH to around 5.0. Mulch azaleas with shredded leaves, leaf mold, pine needles, or pine bark mulch keep the soil cool and moist. Shredded hardwood mulch tends to raise soil pH (less acidic).

Prune azaleas just after they finish flowering. Remove all dead, diseased, or weak branches. New buds for next spring’s flowers form in midsummer.

Azaleas shed some of their evergreen foliage naturally. Leaves may turn yellow, red, or purple before dropping. During unusually cold winters, some cultivars may drop more leaves than in mild winters. Flower buds can also be damaged by cold, dry winds. Deer and rabbits will browse over the winter months.

Common pest and disease problems:

Azalea lace bug appears anytime from spring to fall. Insecticidal soaps, horticultural oils, or systemic insecticides manage outbreaks of lace bugs.

If leaf edges are notched, black vine weevil may be the problem. The nocturnal feeding weevil larvae feed on azalea roots at night. Apply pesticide containing ingredient Imidacloprid to manage black vine weevils.

Azalea petal blight may show up when spring weather is unusually wet. Apply a fungicide labeled for petal blight just as the petals begin to show color.

Phytophthora or Pythium root rots may occur if soils are heavy clay and are poorly drained. Amending the soil to improve drainage may help or plant in raised beds.

Fall Bloom-a-Thon® Lavender azalea

Partridgeberry – Evergreen Groundcover For Deep Shady Areas

Posted by Hugh on March 28th, 2017

Partridgeberry (Michella repens) (photo credit: Mt. Cuba Center)

Partridgeberry (Mitchella repens) is grown for its evergreen foliage, spring flowers and winter berries. This native low-growing groundcover can be found in moist woodlands and along stream banks in the Eastern and Midwest U.S. It is a good choice for planting in deep shaded garden areas (USDA hardiness zones 4–8).

In the spring woodlands, small four-petaled white tubular flowers are arranged in pairs above the foliage. Bright scarlet red berries follow late summer, fall and winter. Partridgeberry may re-bloom lightly in fall.

Partridgeberry is a creeping evergreen perennial up to 2 inches high. Round, 1/2 inch wide, bright green leaves form a dense cover all year. Stems root into the soil where they touch and grows non-aggressively. Bare root plants should be set in very early spring and kept irrigated until the new growth has definitely started. Container plants (plugs) may be set at any time.

Grow partridgeberry in full or partial shade and in compost-rich, acidic, well-drained soil. When first planted, young plants need low to moderate watering. Plants become quite tolerant of dry soils after one season. If you observe leaf wilting, irrigate more frequently or move to a shadier site.

Decorative value: Occasionally, I’ve seen partridgeberry utilized in Christmas greenery for the festive bright red berries and dark evergreen foliage. Fruits are favorites of all kinds of woodland wildlife including deer. However, deer cause little damage to the overall vine.

Keep Your Eye on Red Buckeye

Posted by Hugh on March 25th, 2017

Red buckeye (Aesculus pavia)

Red buckeye (Aesculus pavia) is shrubby or low branching tree maturing to a 15 – 20 feet in height and spread. This southeastern U. S. native is becoming more recognizable as a good choice as a landscape tree for a small urban garden. Plant the tree in either full to partial sunlight and in average well-drained soil.

A tree may develop flowers when it is young in late April and May. Numerous 5 to 9 inches long floral heads sit at branch tips like decorative candles. Bloom count is highest in full day sun. Flowers open slightly before leaf emergence. Flower color on individual trees varies from dark pink to scarlet red. A yellow flowering form is known to exist. Hummingbirds arrive in time to pollinate the individual tubular blossoms.

Lovely palmate compound dark green leaves clothe the branches in spring thru early summer. In late September the broad seed pods split open exposing polished dark buckeye seeds; they drop from the tree, and are quickly grabbed up by squirrels and other garden critters. Don’t be surprised to find a young seedling or two germinating somewhere in the landscape in the years ahead.

Several disease and insect problems riddle the foliage; dry and hot summer weather will often scorch leaf edges unless irrigated weekly. Leaves succumb to the disease and weather onslaught resulting in premature leaf loss beginning in mid-August. Count on no autumn foliage color as branches are typically bare. Spraying pesticides to prevent diseases and insects is unnecessary. New flowers and foliage emerge unharmed the following spring. Deer and rabbits do not trouble this tree.

Pruning, if needed, is performed in mid-spring, right after flowering. Feed the tree lightly with 10-10-10 fertilizer (or equivalent) either before or following spring bloom.

Basic Care Tips In The Spring Perennial Garden

Posted by Hugh on March 22nd, 2017

Coreopsis, Shasta daisy and Beebalm Summer Display

Echinacea x ‘Cheyenne Spirit’

In late winter – early spring, after the snow has melted and daytime temperatures are steadily above freezing, let’s get busy with the cleanup in the perennial garden. First, if you garden in a severe winter region such as zones 4 or colder, remove all winter protection such as evergreen boughs or protective mulches. Many perennials need sunlight as they peak through the ground.

All leaf and twig debris, dead flowers, stems and seed heads should be pruned off. Perennials, such as tickseed (Coreopsis), shasta daisy, garden phlox, asters, and coneflowers (Echinacea), form green rosettes; new flowering shoots will sprout up as sun and warm temperatures reach them.

Weeding garden beds should be your next chore. It may be difficult not to confuse weeds from newly emerging perennials. Follow-up with fertilizing and mulching garden beds. Organic-based slow release fertilizers are preferred as nutrients are metered out over the growing season. Avoid fertilizing plants if the foliage is wet so as not to burn the tender spring growth.

Apply 2-3 inches of pine bark or pine straw mulch near plant but don’t pile mulch around the plant base. Using compost as mulch supplies nutrition for early spring wildflowers such as bloodroot, primula, Virginia bluebells, trilliums and many others.

If needed, divide or transplant newly emerging perennials in the early spring. It’s best to divide most perennials when they are about 2 to 4 inches tall. Never move or divide perennials when they’re flowering. A certain number of perennials are best divided after they bloom. That list includes hostas, oriental poppies (Papaver), Siberian iris, bearded iris, lilies (Lilium) and daylilies (Hemerocallis). Peonies are best divided in the fall.

You may need to stake tall growing perennials using cages or hoops for peonies, Joe Pyes (Eupatorium spp), and baptisias (false indigo). Remove spent flowers from tulips, daffodils, and other spring-flowering bulbs, but let the foliage to die down naturally. Think of bulb leaves as solar collectors to replenish food energy in the bulb for next spring. Do not braid the leaves.

Winter Daphnes Can Be A Rewarding Challenge

Posted by Hugh on March 20th, 2017

Daphne odora ‘Aureo-marginata’

D. odora ‘Aureo-marginata’

Native to China and Japan, winter or fragrant daphnes (Daphne odora) open to light pink or white flowers in winter and early spring in the southeastern U.S. and Pacific Northwest (USDA hardiness zones 7-9). Their welcome floral fragrance will pervade through your garden for nearly two weeks starting in late winter.

Winter daphnes grow 3 to 4 feet high and spread. Flowers, mostly available in white and pink, are produced in small clusters on stem tips. When possible, place daphnes near a patio, deck or walkway where its floral fragrance can be enjoyed.

Glossy dark green leaves are leathery, evergreen, and vary from 1.5 to 3.5 inches in length. Variegated cultivars are edged either white or gold. On a rare occasion, plants bear fleshy non-edible red fruits which are few and far between.

Planting site must be exceptionally well-drained, be generously amended with compost, mildly acidic soil (pH 6.0-7.2), and kept adequately watered. Daphnes are notoriously finicky shrubs and don’t tolerate dry or poorly drained sites. Overwatering leads to their rapid demise. Plants also flourish in containers when properly cared for.

Set in one-half day, preferably in the early morning hours or in dappled shade. Daphne leaves will sun scorch when not adequately shaded. In warm climate zones, the further south you live, the plant should see less afternoon sunlight. Daphnes require only minimal pruning and spring is a good time, anytime after flowering.

Aphids and scale insects are occasional pests. Root rot, crown rot, and leaf-spots are fungal diseases, mostly caused by poor environmental growing conditions.

Leading varieties:

‘Aureo-marginata’ – rosy-pink flower buds that open to white with slight cream-colored edge leaves.

‘Alba’ – white flowering form.

‘Zuiko Nishiki’ – green leaves, heavier bloomer than species, more fragrant, and reportedly is hardier.

Annual Flowering Vines

Posted by Hugh on March 17th, 2017

Exotic love vine (Mina lobata)

Thunbergia ‘Sunrise Surprise’

This spring try vertical gardening. There are a number of annual flowering vines that grow in either the ground or in a large container. Some offer cooling shade on a deck or patio. Vines are highly ornamental with attractive flowers, foliage, and/or fruits.

Annual vines grow quickly after planting. Plant seeds of these vines at the base of the trellis as soon as soil has warmed in April and May. For a dense cover, space seedlings 6 to 12 inches apart. In northern areas, where growing season is short, some vines like morning glory and hyacinth bean vine should be started from seed indoors and transplanted outside when threat of spring frost has waned.

Most annual vines climb by twisting around a support. Some attach themselves by means of wrap-around tendrils. Trellises come in many shapes and sizes, constructed of wood or metal. Supports can be simple from a single length of wire or sturdy twine (jute) cord. How about construct a support that mimics a spider’s web.

Annual vines have specific growing needs. For example, sweet pea vines bear clusters of flowers in late spring and early summer (depending on region of the country). Flowers come in a wide choice of colors (red, pink, blue, white and purple), are highly scented, and make excellent cut flowers. Sweet peas stop blooming and vines wither in hot dry weather.

For most vines full sun and an organically rich soil (or potting medium) are perfect. In hot weather climates, provide partial shade in the afternoon. Mature size will depend on plant species; some vines may reach to 15 to 20 feet by autumn. Pinching off the terminal tips will encourage branching. In the first 4 to 6 weeks train the direction of growing shoots with ties. Most vines benefit from monthly feeding with a water soluble fertilizer such as Miracle-Gro™, Schultz™, Daniels™.

Cup and Saucer Vine, Cathedral Bells (Cobaea scandens)

Hyacinth bean vine (Dolichos lablab)

Hyacinth Bean Vine (Dolichos lablab)

Moon Vine (Ipomoea alba)

Cypress Vine, Hummingbird Vine (Ipomoea quamoclit)

Morning Glory (Ipomoea tricolor)

Sweet Pea Vine (Lathyrus odoratus)

Spanish flag, exotic love vine (Mina lobata)

Scarlet Runner Vine (Phaseolus coccinea)

Black-eyed Susan Vine (Thunbergia elata)

Galax- Popular Mountain Plant For Your Woodland Garden

Posted by Hugh on March 13th, 2017

Galax in Western North Carolina Woods (photo by Bob Hale)

Galax (Galax urceolata) is an under planted perennial wildflower native to the southern Appalachian mountains and eastern U.S. (USDA hardiness zone 5). Galax foliage is frequently collected from the wild for use in the winter floral decorations. Unfortunately, over-harvesting on public lands has jeopardized wild populations.

Galax grows 6 to 12 inches tall and is recognized for its dark evergreen glossy leaves which are round to heart shaped. The glossy round leaves of galax often turn a beautiful burgundy color in winter, particularly if weather is extremely cold and lacking in snowfall.

Galax is sometimes called “wandflower”. In late spring (June in SW Virginia, Western NC and East Tennessee) white flower spikelets emerge through the foliage on leafless stalks or “wands”.
The flower spikes, adorned with tiny white flowers, rise 9-12 inches above the dark glossy green foliage.

Galax grows best in cool, moist, well-drained, mildly acidic woodland soil. Allow galax 2 – 3 years to establish. Vigorous plants will slowly colonize and eventually form a dense carpet in your woodland garden. Long term success is built on soil moisture and not on how much you fertilize it. Mulching with pine needles helps to acidify soils over the years. Do not allow fallen leaves to smother the planting

Galax is a wonderful woodland ground cover and deserves greater landscape use. Deer will occasionally browse planting(s). Mt. Cuba Center in Greenville, Delaware recommends planting with Eastern teaberry (Gaultheria procumbens), Rosebay rhododendron (Rhododendron maximum), Mountain laurel (Kalmia latifolia), bellwort (Uvularia spp.) and crested iris (Iris cristata).