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

Five Reliable Summer – Early Fall Flowering Perennials

Posted by Hugh on May 18th, 2017

Phlox ‘Jeana’ attracts butterflies

‘Fireworks’ goldenrod at NC Arboretum, Asheville, NC

Planning a new perennial garden this summer?Include these five very dependable flowering perennials. All are low maintenance and are U.S. natives (USDA Zones 4–8).

‘Zagreb’ (Coreopsis verticillata) has a very uniform plant habit and finely dissected foliage. Plant grows only about 20 -24 inches tall, and is blanketed with bright yellow (gold) flowers coupled with fine-textured foliage. Zagreb grows more compact and uniform habit compared to species.

‘Summer Sun’ heliopsis (Heliopsis helianthoides), also called ‘Sommersonne’, provide long-lasting beauty throughout the summer. Plant grows 2 -3 feet tall and 2 feet wide with strong stems topped with ruffled golden flowers.

‘Jeana’ garden phlox (Phlox paniculata) produces sweetly scented 6- inch long lavender-pink flowers. The fragrant florets are soft pinkish-lavender with a darker wine colored eye. Plant typically grows as a clump to 2-4 feet tall and 3 feet wide on stiff stems clad with 3-4 inch long deep green leaves. Foliage is highly resistant to powdery mildew.

‘Bluebird’ aster (Symphyotrichum laeve), formerly Aster laevis, produces abundant, violet blue flowers with yellow button centers on 3-4 feet tall stems in September-October. Its attractive bluish-green foliage is virtually pest-free. In mid-June prune back the vigorous growing stems by one-half to encourage branching and compactness.

‘Fireworks’ goldenrod (Solidago rugosa ‘Fireworks’) is a striking, clump-forming perennial with stiff lateral golden yellow flowers in early to mid-autumn. This dwarf growing selection grows only 3-4 feet tall and blooms over 2-3 weeks. Include in a container, garden border or meadow.

All five perennials perform best in full sun and in moist, compost-rich, well-drained soil. All tolerate poor to average soil if drainage is good. All are moderately drought tolerant after first year in the garden. Three of five perennials will bloom into autumn if old spent blooms are quickly removed (deadheaded).

All perennials attract butterflies, bees and other nectar gathering insects into your garden. Bring cut flowers in for fresh and dried arrangements.

Tidying Perennials After Blooming Is Over

Posted by Hugh on May 15th, 2017

Clean-up of Old Blooms in Lambs ears (Stachys byzantina)

Clean-up Old Blooms in Lambs ears (Stachys byzantina)

Heuchera flower scapes

“Deadheading”, the practice of removing the old or spent flowers, can be utilized to improve the appearance of many perennials. These perennials do not rebloom after deadheading, but plants look alot better after the cleanup. Daylilies (Hemerocallis cv.), coral bells* (Heuchera spp.), and hostas (Hosta spp.) are prime examples of perennials that benefit from clean up after deadheading.

The flower or plume stalks of many perennials are highly ornamental and can be left to enjoy. Many ornamental grasses are examples here. On others, you risk the dispersal of unwanted seeds which frequently become next year’s weed problem in your garden.

Gardeners opt to remove flower stalks to put all the plant’s energy into the foliage. The following list is not complete, but includes most popular perennials.

Bear’s breeches (Acanthus spinosa)

Bugbane (Actaea podophylla)

Bishop’s weed, goutweed (Aegopodium podagraria)

Japanese anemone (Anemone × hybrida)

Lady’s mantle (Alchemilla mollis)

Goat’s beard (Aruncus dioicus)

Astilbe, False spirea (Astilbe spp.)

False indigo (Baptisia australis)

Bergenia (Bergenia cordifolia)

Queen of the Meadow, Meadowsweet (Filipendula ulmaria)

Cranesbill, Wild geranium (Geranium spp.)

Lenten Rose or Hellebore (Helleborus x orientalis)

Daylilies (Hemerocallis spp.)

Coral bells (Heuchera spp.)*

Rose mallow (Hibiscus moscheutos)

Hostas (Hosta spp.)

Irises (Iris spp.)

Leopard plant, Ligularia (Ligularia spp.)

Catmint (Nepeta × faassenii)

Herbaceous Peony (Paeonia spp.)

Obedient plant (Physostegia virginiana)

Lungwort (Pulmonaria spp.)

Lambs’ ears (Stachys byzantina)

* There are two forms of coral bells, those with showy flowers (average foliage) and those with lush colorful foliage (non-showy flowers).

After deadheading apply a water soluble fertilizer such as Miracle-Gro™ or Schultz™. This is good time to clean up the bed, remove weeds, and add organic mulch. If ground is dry, water deeply the perennial bed by irrigating overhead (equivalent of 1 ½ inches of rainfall) for 3 – 4 hours.

Act Quickly Against Eastern Filbert Blight

Posted by Hugh on May 11th, 2017

Susceptible ‘Contorta’ filbert

Black stromata lesions

European Hazelnut (Corylus avellana) is highly prized both for its edible nuts and as a landscape shrub/small tree. Unfortunately, it is susceptible to eastern filbert blight (EFB). American hazelnut (C. americana) is relatively resistant.

EFB is a lethal disease as it may kill a large shrub in 4-5 years. The fungus was discovered in the Pacific northwest on commercial hazelnut trees and contorted filbert, var. ‘Contorta’, aka ‘Harry Lauder’s Walking Stick’, a popular landscape shrub (USDA hardiness zones 4-8). EFB is also prevalent in the eastern U.S.

Canker sores (elliptical black stromata) are the key symptoms. Susceptible trees with many cankers must be removed as soon as possible. On American hazelnut small cankers will form on its branches, but do not lead to an extensive dieback as observed on European species.

The fungus disease emerges in spring as a milky ooze and is carried by wind-driven rain and splashing raindrops to other branches and to nearby trees. The fungus invades the phloem and outermost layers of xylem. The cankers appear on the surface of the branch 12-18 months later. Infection worsens during long periods of high humidity and occurs over a wide range of temperatures.

Inspect shrubs in winter for cankers and in July and August for dead or dying branches. Infected branches should be pruned 18 inches past the canker. All cut branches should be burned or removed from the property. Treat with chlorothalonil fungicide (such as Daconil, other brands) at spring bud break and every two weeks through the spring season.

European hazelnuts are valued for their highly prized nuts. Native hazelnuts do not produce high quality nuts, but are valued as a wildlife food source. European hazelnut orchards are produced primarily in the Pacific Northwest.

‘Red Dragon’, a red leaf cultivar of C. avellana ‘Contorta’, is resistant to eastern filbert blight. It grows 5-8 feet tall and 8-10 feet wide (USDA hardiness zones 4-8).

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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