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

Chinese Fringetree Is Versatile Landscape Tree

Posted by Hugh on May 8th, 2017

Chinese fringetree at J.C. Raulston Arboretum in Raleigh, NC

May flowering in Johnson City, TN

Chinese fringetree (Chionanthus retusus) is native to China, Korea and Japan (Zone: 6 to 9a). Related to native U.S. species (C. virginicus), fringetrees are noted for their profuse spring bloom of fragrant white flowers. It is most often seen in cultivation as a large, multi-stemmed, deciduous shrub growing to 15 – 20 feet tall with a rounded, wide-spreading form. It also may be grown as a small to medium tree (multi-trunked or trained as a single trunk), maturing to 30 – 40 feet tall.

In late spring, terminal clusters pure white 4 inch flowers are mildly fragrant. It flowers about 1-2 weeks earlier than native fringetree. Plants are primarily dioecious (separate male and female plants), but may bear some perfect flowers. Male flowers tend to be slightly larger.

Female flowers bear clusters of ½ inch long olive-like fruits that ripen to bluish black in late summer/fall and serve as a good food source for birds and other wildlife. Lustrous, leathery oval to round leaves are bright green above and ashen green and downy beneath. Leaves turn yellow in fall (reportedly more attractive in northern areas). Glossy gray-brown bark on young trees exfoliates in thin curls and is an attractive winter feature.

All fringetrees bloom best in full sun to part shade and in average, medium moisture, well-drained soil. Foliage is tolerant of air pollution and adapts well to urban settings. It exhibits good drought tolerant once planted for one year. Irrigation over long dry spells lasting many weeks is highly recommended.

Chinese fringetree has no serious insect or disease problems. Occasionally, mites, scale, and borers maybe problems, particularly when planted on an inhospitable site.

‘Tokyo Tower’ is a unique columnar small flowering tree. Branching habit is very fastigiate (upright). On species trees, pruning is performed after flowering. Tokyo Tower rarely needs pruning, other than to maintain its unique stove-pipe appearance.

U.S. Native Bleeding Hearts Dazzle In Woodland Garden

Posted by Hugh on May 5th, 2017

Dicentra exima (unknown cultivar)

One of nature’s delights in the late spring – early summer garden is the wonder of bleeding hearts (Dicentra spp.) in bloom (USDA hardiness zones 3-9). Fringed bleeding heart (D. exima) is a U.S. native to the Appalachian Mountains. Fringed bleeding heart exhibits deeply-cut, fern-like, grayish-green foliage on 10-15 inch tall plants. Dangling bright pink pendant (or heart) flowers are supported on arching stems. Flowers and plant size are smaller and leaves more deeply cut than its Asian cousins. Clumps continue to grow through summer compared to Asian species which disappear upon arrival of summer’s hot dry weather.

White-flowered cultivar ‘Alba’ with pale green foliage is a popular selection. Dr. Alan Armitage describes the cultivar named ‘Margery Fish’ for its white flowers and blue-green foliage on 10 inch high x 12 inch wide plants (zone 5) . He also singles out ‘Dolly Sods’ as a topnotch performer, particularly in Southern gardens; latter features blue-green leaves and heavy numbers of pink flowers. Popular cultivar ‘Luxuriant’ is likely a hybrid form. It grows 15-18 inches tall with pink flowers and dissected foliage; it often re-blooms during a late summer weather cool-down.

Plant in full to partial shade in compost-rich mildly acidic to slightly alkaline soil (6.0 -7.5 pH range). Soil drainage, particularly in clay soils must be well-drained; plants seem to linger or decline in too wet ground in winter. Garden centers usually sell dormant roots in packages or already growing in containers. Space plants or roots 18-24 inches apart in shade or part shade. Mulch lightly. In warm regions plants may die back and become dormant by late summer.

Clipping back plants to 4-6 inches after bloom usually will usually stimulate new foliage and spur a second flush of flowers in late summer. Flowers attract butterflies and hummingbirds. Aphids, slugs and snails occasionally feed on the leaves. Plants are deer and rabbit resistant. Bleeding hearts may self-sow in the garden.

Overcrowded clumps (rhizomes) may be divided in spring or fall. Best time to divide is just after flowering is complete or in very early in the spring before buds emerge. Dig up rhizomes, section into 2-4 buds (or eyes), and replant. Mix in several shovelfuls of rich compost to replenish the ground and lightly feed with a slow-release fertilizer. Light mulching is highly beneficial.

Bleeding hearts compliment other woodland plants such as ferns, lungwort (pulmonaria), brunneras, coral bells (Heuchera), and foam flowers (Tiarella).

Bigroot Geranium

Posted by Hugh on May 3rd, 2017

Bigroot Geranium

G. macrorrhizum ‘Ingwersen’s Variety’

Bigroot geranium (Geranium macrorrhizum), aka “cranesbill”, is a clump-forming perennial ground cover from Southern Europe (USDA Zones 3–8). It is one of the easiest geraniums to grow. Plants spread by thick rhizomes to form a dense ground cover. Individual plants grow 12 to 18 inches high and 18-24 inches spread.

The 1-inch wide, 5-petaled dark purplish pink (magenta) flowers appear in late spring. This cranesbill often re-blooms in summer. Flowers give way to cranesbill-like seed heads. Deeply lobed palmate, deeply-lobed (5 – 7 lobes), medium green leaves (basal leaves may be 4 – 8 inches wide) are hairy, sticky and fragrant when crushed. Leaves take on an attractive bronze tint in fall. Foliage forms an attractive ground cover throughout the summer and fall. Leaves are also fragrant when crushed. Species is called “bigroot geranium” in reference to its thick, fleshy rhizomes.

Bigroot geranium is easily grown in average, dry to medium, well-drained soils and in full sun to partial shade. One year established are very drought tolerant and hold up to summer heat better than most Geranium spp. Raise the height of the lawn mower to 9 – 12 inches high and mow over the planting to removal of spent flower seedheads to obtain an attractive plant appearance and slow possibilities of self-seeding. Feed lightly with 10-10-10 or equivalent fertilizer in early spring.

In general, geraniums as a group have few serious insect or disease problems. Poorly drained, infertile soil and extreme weather conditions will slow down this otherwise carefree ground cover. Rabbits and deer usually leave it alone

Plant this as a reliable ground cover in partially shaded areas of flower garden or around the base of recently planted trees. It grows aggressively, easily naturalizes, and chokes out weeds.

Leading Varieties:

‘Bevan’s Variety’ is a popular cultivar; it tends to grow an inch or two taller than the species and is slightly more vigorous.

‘Ingwersen’s Variety’ has light pink flowers and slightly glossier leaves.

Korean Maple Substitute For Fullmoon Japanese Maple

Posted by Hugh on April 30th, 2017

Acer pseudosieboldianum ‘Takeshimense’

Fall color starting in mid-October

At first sight Korean maple (Acer pseudosieboldianum), aka Korean fullmoon maple, is very similar in appearance to fullmoon Japanese maples (A. japonicum var. Acontifolium). If you live in a northern U.S. such as the upper Midwest, growing Japanese maples will likely become an unfulfilled wish. Korean maple is a hardier choice for northern locales (USDA hardiness zones 4-8).

Korean maple forms a lovely small multi-trunk tree or large shrub. It matures to 15-25 feet tall and 15-20 feet in spread. Foliage is similar to A. japonicum, featuring 3- 5 inch diameter circular leaves edged by 9-11 lobes. Summer leaves are a rich forest green that transitions in autumn to yellow, orange, scarlet, or red; fall leaf color is dependent on environmental factors in your area.

Korean maple prefers a moist, organically rich, well-drained soil and in full sun to partial shade. In the mid-South (zones 6 and 7) the tree does best in half-day sun. Its heat and drought tolerance across the deep South is mostly untested; likely it might prefer a dappled sun site. In colder latitudes, lay down a blanket of organic mulch around Thanksgiving to protect the tree’s root zone from temperature extremes.

Pruning needs are occasional, mostly to develop plant form and size. Korean maple has no serious insect or disease problems. On the disease side, stem canker, leaf spots, tar spot and anthracnose may occur. Watch for aphids, borers, scale, leafhoppers, caterpillars and mites.

Cultivar: ‘Ullung-do Island’ (var. ‘Takeshimense’) grows 20 -25 feet tall and 15-18 feet wide. This selection tends to grow multi-branched. It originates from the Ullung-do Island in the sea of China.

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.