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

Summer Heat And Drought Tolerant Annuals

Posted by Hugh on April 27th, 2017

Petunias and Calibrachoas are moderately drought tolerant

Globe amaranth – Very drought tolerant

Annuals (bedding plants) provide many more weeks of colorful flowers and/or foliage than perennials and woody landscape plants. Planting a fabulous flower garden does involve lots of initial preparation, including adding lots of organic matter (compost) to the ground and tilling it in.

First, plan your summer flower garden before you plant. Choose those that are heat and drought tolerant. Many regions of the U.S. continue to suffer through drought. Many urban areas are either limiting or have totally banned watering of flower gardens.

Specific drought tolerant annuals are the ones to choose (see list below). They ask for very little maintenance other than planting into an organically rich well-drained soil and in full or partial sun. Most promise good summer heat and drought resistance provided they have been “babied” or cared for during their first 4-6 weeks after spring planting. April and May rainfall is generally plentiful. Primary care is weekly watering, bi-weekly feeding with a water soluble fertilizer (such as Miracle-Gro™, Daniels™, or Espoma™). You may substitute feeding with a slow release fertilizer such as Osmocote™ or Nutrikote™ applied at planting time. All flowers should be mulched with 3-4 inches of an organic mulch such as wood bark or pine needles.

These 10 annuals are exceptionally drought tolerant:

Vinca (Catharanthus roseus)

Spider flower (Cleome hyb.)

Mexican heather (Cuphea hyssopifolia)

Silver Nickel Vine (Dichondra argentea ‘Silver Falls’)

Euphorbias (Euphorbia x)

Globe amaranth (Gomphrena globosa)

Lantana (Lantana x)

Moss Rose (Portulaca grandiflora)

Lemon Coral Sedum (Sedum rupestre Lemon Coral™)

Mexican Sunflower (Tithonia rotundifolia)

These 12 annuals also tolerate very hot summers, but demand moderate 1 to 1 ½ inches of water every 10-12 days if natural rainfall is absent.

Joseph’s Coat (Alternanthera spp.)

Summer snapdragons (Angelonia)
Ornamental Pepper (Capsicum annuum)

Cockscomb (Celosia argentea)

Marigold (Tagetes spp.) ‘
Starflower (Pentas lanceolata)

Fountain grasses (Pennisetum spp.)
Salvia (Salvia spp.)

Mexican Bush Sage (Salvia leucantha)
Fan Flower (Scaevola aemula) – Surdiva® or Bombay® series

Wax Begonia Big® and Whopper®

Star zinnia (Zinnia angustifolia)

Gardenias Continue To Disappoint In The Mid-South

Posted by Hugh on April 24th, 2017

Potted Gardenia- tree form

Gardenia clipped at Charlotte NC restaurant

The lure of fragrant white flowers have mid-South gardeners (zones 6 and 7) wanting to grow gardenias (Gardenia jasminoides). New cultivars, supposedly hardier than previous ones, hit garden centers every spring. Unfortunately, zones 6 and 7 winters usually prove them wrong.

Recent purchases of new cultivars ‘Frostproof’ and Pinwheel® and older selection ‘Kleim’s Hardy’ have proven disappointing here. Plants appear to dread wild temperature fluxes so common.

Native to semi-tropical areas of Asia (USDA hardiness zones 8-11), gardenias are slow-growing evergreen shrubs. Hardy forms supposedly may grow outdoors where winter temperatures are mild (zone 7, maybe 6). In most regions of the U.S., they should be brought indoors in winter and grown as a house plant.

Plant gardenias in an area to catches morning to early afternoon sun or all-day dappled sunlight. Protect gardenias from mid-afternoon sun. Gardenias prefer an acidic soil ranging from pH 4.5 to 6.0. Alkaline soil pH often causes chlorosis (interveinal yellowing) and reduces bloom count. Yellowing and shedding of older leaves occur before or after flowering. To increase soil acidity add elemental sulfur, chelated iron and/or aluminum sulfate. Lightly prune after bloom to shape and develop a dense shrub. Do not prune after mid-August.

Wherever you live, treat gardenias as finicky house plants. They’re troubled by spider mites, mealy bugs, scales, aphids and white flies. If you observe sooty mold growing on stems or leaves, white flies and aphids are likely feeding. Inspect plants often and spray with insecticidal soap or neem oil when pests are seen.

Plants are challenging to grow inside most homes and are best cared for a greenhouse or sunroom. Provide an east or south sunlight exposure over the winter months. Feed with a fertilizer for acid-loving plants such as Miracle-Gro™, Espoma™, or Daniels™ every 2-3 weeks in spring and summer. Allow plants to spend summer outdoors (mid-May through September in most locales) under the dappled shade of shade trees in your yard. From late fall through winter, feed plants monthly.

Overwatering is the greatest problem with growing gardenias. Plants don’t like their roots embedded in soggy soils. Repot gardenias in containers in late winter or immediately after flowering. Root pruning (removal of dead or browning roots) should encourage new roots.

Quest For The Perfect Tomato Continues

Posted by Hugh on April 21st, 2017

Mountain Pride’ tomatoes at Farm Market

Improved disease resistance, fruit color, firmness, and flavor continues to be the main goals of tomato breeders around the U.S. Leaf and root diseases vary from one region to another across the country. Here in the eastern U.S., late blight resistance is of key interest.

Over the past 33 years, Dr. Randy Gardner, tomato breeder extraordinaire in western North Carolina, has developed over 25 varieties. Some of his most popular varieties include ‘Mountain Pride’, ‘Mountain Spring’, ‘Mountain Fresh’, and ‘Mountain Majesty’. The latter variety has really nice flavor and exhibits exceptional red fruit color.

Tomato abnormalities

Gardner’s newest grape tomato variety, ‘Mountain Honey’, exhibits great flavor and disease resistance. Vines are indeterminate, e,g., bear fruits all summer long with higher sugar content compared to many grape tomato varieties on the market.

Tomato breeders are focused on improving old-timey varieties. Gardeners call them “heirlooms”. Gardner is no exception, focused on improving heirlooms for fruit appearance, less fasciation (a lobed shape), more disease resistance, increased firmness (less cracking), and a smaller inner core, while retaining their traditional flavor and eating quality.

Looking ahead to 2018, he will release ‘Mountain Rouge’ which performed better in trials compared to common heirloom varieties ‘Cherokee Purple’, ‘Pink Brandywine’, and ‘Mr. Stripey’. Many heirloom varieties were susceptible to late blight late in the harvest season. Mountain Rouge retains the super flavor of ‘Pink Brandywine’.

A rising trend at produce markets is regional branding of tomato varieties. In the future a popular California variety may not sell as well in a New York market. East coast customers prefer the flavor of the heirloom tomatoes, and tomato breeders are working to improve their yields while keeping their flavor.

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prefer striped type heirloom varieties. Those sold for a fresh market tend to be less firm, softer flesh, and thin skinned; they don’t need to be shipped long distances. Multi- purpose varieties may serve several cuisines……

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Tips On Planting Landscape Trees or Shrubs

Posted by Hugh on April 18th, 2017

Newly planted tree (note use of too much mulch)

newly set shrubs

For some senior gardeners, planting a tree or shrub in your landscape may be a difficult task. The loss of a newly planted tree may be expensive as well as heartbreaking. Following proper planting techniques should avoid any mistakes.

Here are a few tips to make the job a lot easier. No need to dig deep holes…. shallow wide holes are better. Planting hole is the same depth as plant grew in the nursery. Avoid planting trees and shrubs too deeply.

Dig the hole three times wider than the root ball. Plant the tree green side up in the hole and back fill with the original soil removed from the hole. The uppermost topsoil should be placed back into the bottom of the hole.

What to plant? Select the desired plant hardy in your area. Determine the plant zone where you live on-line. Plant zone information is listed on the plant tag. Never assume that the local garden center is selling only plants that are hardy in your region. This is not always the case. Know your heat zone rating, soil type and drainage. You also may need to irrigate certain times of the year.

With balled and burlapped (B&B) shrubs and trees, remove wire baskets and twine. Leave trunk wrap on if tree is planted in fall, and remove by summer of the following year. With container grown trees, untangle masses of roots before setting in the planting hole. Don’t buy tightly root bound container plants.

Bare-root trees should be planted in late winter to early spring before they begin to leaf out. Soak the container in water for 8-24 hours and spread out roots prior to planting. Remove circling roots that may girdle the tree many years from now.

Mulch newly planted trees – apply 3-4 inches of an organic mulch and keep it away from the trunk. Bark or wood chips and pine needles are good choices, and new sawdust or wood shavings are a huge mistake as these materials rob the soil of nitrogen.

Watering in your new tree is the last and most important step. A two inch caliper tree may require 5-7 gallons of water. If there is no rainfall after one week, repeat this step. You may need to water again over long dry spells lasting 10 days or more. Your tree(s) should be well established after one year.

ACS SOUTHEAST REGION CONIFER REFERENCE GARDENS*

Posted by Hugh on April 15th, 2017

Taxodium ‘Cascade Falls’

Conifer mix on a property in Waynesboro, VA

I hear people say that conifers won’t grow in the southeastern U.S. Wanta bet!

2016 marks the 8th year of the Reference Garden program sponsored by the American Confer Society (ACS)- Southeast Region. From Kentucky and Virginia south to Florida, 19 public gardens were now participating in the program. Two of the latest additions are Brookgreen Gardens (Murrells Inlet, SC) and Lockerly Arboretum (Milledgeville, GA).

Since 2009, ACS Southeast Region has awarded 21 grants totaling more than $30,000 to the Reference Gardens. The program is funded by the proceeds from regional meetings and auctions. To join the Reference Garden program, a garden must meet certain criteria and agree to submit a short report annually summarizing their conifer related activities.

Despite record heat, drought and excessive rainfall in many areas of the Southeast, Reference Gardens report that more than 600 conifers were planted and a myriad of programs were presented. The ACS Southeast Region Reference Gardens program is helping to spread the word that conifers are a great landscape option in Southern gardens. Here is the latest list of participating gardens:

Gardens of the Big Bend, Quincy, FL

Atlanta Botanical Garden, Atlanta, GA

Armstrong State University Arboretum Conifer Garden, Savannah, GA

Lockerly Arboretum, Milledgeville, GA

Smith-Gilbert Gardens, Kennesaw, GA

The State Botanical Garden of Georgia, Athens, GA

Baker Arboretum, Bowling Green, KY

JC Raulston Arboretum, Raleigh, NC

Brookgreen Gardens, Murrells Inlet, SC

Hatcher Garden-Woodland Preserve, Spartanburg, SC

Moore Farms Botanical Garden, Lake City, SC

East Tennessee State University Arboretum, Johnson City, TN

Memphis Botanic Garden, Memphis, TN

University of Tennessee Gardens, Knoxville, TN

West Tennessee Research and Education Center Gardens, Univ. of TN Jackson, Jackson, TN

Al Gardner Memorial Conifer Garden, Reynolds Community College, Goochland, VA

Lewis Ginter Botanical Garden, Richmond, VA

Norfolk Botanical Garden, Norfolk, VA

State Arboretum of Virginia, Boyce, VA

*excerpted from report appearing in March 2017 ACS Newsletter by Barbie Colvin, SE Reference Garden Committee Chair.

Virginia Sweetspire — A Standout Native Shrub

Posted by Hugh on April 12th, 2017

Virginia sweetspire in May Garden

Fall leaf color of Virginia sweetspire

Virginia sweetspire (Itea virginica) is a native shrub that touts showy white raceme flowers in late spring and brilliant reddish purple foliage in fall (USDA hardiness zones 5-9). Flowers are very fragrant and attracts hundreds of bees and other pollinators.

VA sweetspire excels in moist, humus-rich, mildly acidic soils (pH 5.2-6.5). In its native habitat, this rambling shrub is found growing adjacent to brooks and streams in woodland areas alongside other wildflowers and ferns.

For maximum flowering and intense fall leaf color, grow VA sweetspire in full sunlight and moist soil. It tolerates moderate shade and thrives in average soils. Mulch the ground around the shrub with 3 inches of pine straw, chips, nuggets or other organic material. Once established, usually after one year, this shrub is moderately drought tolerant. Fertilize in spring with a slow release organic fertilizer such as Osmocote™ or Nutrikote™ following package directions.

Hold off pruning until after flowering. Hold this suckering plant to its place and remove old spent flowers to maintain a tidy appearance. Insects and diseases rarely trouble VA sweetspire. If you notice spotting on the leaves, they will likely be harmless. Remove unwanted suckers any time of year. One or two may be dug up and replanted in another location. If suckers are left in place, VA sweetspire will form a wide colony.

Mature plant size is 3 to 6 feet tall and wide, depending on the cultivar. ‘Henry’s Garnet’ is the best-known and is widely grown cultivar at 5-6 feet high and 4-6 feet wide. It thrives in summer heat and winter cold and exhibits excellent flowering and fall color. Put your nose up close to pick up the delightful fragrance. Shorter growing ‘Little Henry’ is 4 – 5 feet tall. ‘Merlot’ grows 4 – 4 ½ feet tall with a deep-red fall leaf color. ‘Saturnalia’ is more upright branched with a standout fall color.

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.