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

Spring – Summer Care of Herbaceous Peonies After Flowering

Posted by Hugh on May 26th, 2017

Spring flowering Peony

White herbaceous peony

Summer weather can be tough on the foliage of tree and herbaceous peonies tree (P. lactiflora). Here are some tips to ensure your peony plants will prosper for many years to come.

Keep foliage disease-free and prune off all badly infected with mildew or black spotted. Some varieties naturally shed their leaves (go dormant) early. Itoh hybrids and most hybrids maintain their foliage very late into growing season. Healthy foliage will build strong roots and increase numbers of flower buds next season.

Fertilize after flowering with granular 10-10-10 or equivalent. Usually 1-2 handfuls spread around the plant is adequate. Keep fertilizer a minimum of 6 inches away for the plant base. Mulch with an organic-based mulch such as chipped bark, composed shredded leaves, or straw to conserve soil moisture and prevent weed competition.

Deadhead your peonies, e.g.,prune off the spent flowers and seed pods. This will improve plant appearance through the long hoy summer ahead. Varieties with large blooms may have fallen over due to heavy rainfall. Many varieties will produce seeds, fall to the ground, and germinate. Eventually, seedlings grow and over time compete with the original peonies.

For foliar mildew problems, clip off all diseased or dead foliage and discard. If your area does not allow burning put it into the trash. Don’t compost diseased plant material since the spores will carry over into next year. Remove from the garden and throw in household trash or burn debris. The dead leaves are full of spores that may injure new spring foliage.

If you have additional gardening queries, contact your local Extension agent. He or she can suggest fungicides are approved in your state for peonies. Master Gardeners may also be knowledgeable area experts.

A great resource for peony information: Hollingsworth Peonies, P.O. Box 517, Hockessin, DE 19707. Telephone number: (302) 635-0140. For general information: nursery@hpeonies.com

Five Perennial Staples For Your Summer Garden

Posted by Hugh on May 23rd, 2017

‘Zagreb’ Coreopsis & ‘Becky’ Shasta daisy

Salvia ‘May Night’

If you are designing a new perennial garden, here are five proven perennials to start out with. All varieties are standout garden performers known for their long blooming period and showy flowers. Coreopsis and veronica are often utilized for edging along a sunny border. All can be planted in mixed containers.

‘Pow Wow Wild Berry’ coneflower (Echinacea purpurea ‘Pow Wow Wild Berry’) – is a distinctive cultivar of purple Coneflower. Plants form a midsized mound of coarse dark-green leaves, bearing large daisy flowers with magenta-pink petals surrounding an orange-brown central cone by midsummer. ‘Pow Wow White’ is a white flowering companion. 24 inches tall and 20 inches wide (Zones 3-9)

‘Zagreb’ Threadleaf coreopsis (Coreopsis verticillata ‘Zagreb’) – forms a spreading clump of very delicate, ferny foliage. This compact selection (12-18 inches tall and wide) bears loads of starry golden-yellow daisies, from early summer into the fall (Zones 4-9).

‘Becky’ Shasta daisy (Leucanthemum x superbum ‘Becky’) – Becky is a tall growing cultivar (36-42 inches high and 24 inches wide). Flowers are large single white daisies with a yellow eye, is excellent for cutting (Zones 4-9).

‘May Night’ Salvia (Salvia x sylvestris ‘Mainacht’) – is a medium grower (18-24 inches high and wide) with deep indigo blue flowers (Zones 3-9).

‘Royal Candles’ Spike Speedwell (Veronica spicata ‘Royal Candles’) – an outstanding upright growing speedwell with large, attractive deep-green glossy leaves and deep purple-blue flower spikes. Other veronicas available in deep purple, pink, and white; highly recommend dwarf pink flowering ‘Giles Van Hees’. Zones 4-8.

All five perennials listed here are easily to care for in full to partial sunlight (minimum 6 hours sunlight) and in average well-drained soils. Plants tolerate long dry periods after their first year in the garden. Expect 4-5 years of good flowering without the need of dividing plants. Deadheading flowers will extend blooming through the summer months. All tolerate summer heat and humidity. Flowers attract numerous bees, butterflies, and an occasional hummingbird.

How Drought Affects Our Landscape Trees*

Posted by Hugh on May 20th, 2017

Leaf shedding of drought stressed tulip poplar (Liriodendron tulipifera)

Long term drought can be devastating on landscape and woodland trees. An environmentally stressed tree must expend additional energy to survive. Extremes of drought leads to decreases in trunk diameter and height growth, declining resistance to pests and diseases, less food production via photosynthesis, and in flower and fruit production. Symptoms of drought stress include wilted leaves, early leaf loss (defoliation), and leaf edge burn / brown leaves.

Drought susceptible sugar maple (Acer saccharum)

While newly planted trees and seedlings are in immediate jeopardy, droughts lasting 1-2 years generally do not kill large well-established trees. Long term dry periods lasting 5 or more years are a different matter, especially mature trees nearing the end of their lives. Stressed trees often die during the following growing season because trees are not able to re-leaf because of depleted energy reserves.

Drought denotes a period without precipitation during which the soil water content is reduced to such an extent that trees suffer. Water deficits in a tree occur when transpiration (the process by which leaves let off moisture and oxygen) exceeds the water amounts remaining to leaves.

Periods of droughts are common in some years in all regions of the U.S. Many landscape trees are stressed by prolonged periods of hot, dry weather. The landscaper’s goal should be to select tree species that utilize water more efficiently without the need for frequent watering (or irrigation). Many municipal water can and will prohibit landscape irrigation during long drought spells. Drought tolerant trees will be healthier and lower in maintenance.

Select trees that use water efficiently. Some examples:

Native trees are better adapted to climate and pest conditions than non-native trees.
Trees with small leaves (linden, elm, willow oak) are more easily cooled and more water-use efficiency than trees with larger leaves (sycamore, cottonwood, basswood, tuliptree).
Upland species are generally more drought-resistant than bottomland species.
Early successional species, those that colonize old fields and disturbed sites (pines, black locust, elms), use water more effectively than late successional species (sugar maple and beech).
Trees with deep, upright crowns are more effective in water use than those with flat, wide-spreading crowns.
Trees with multi-layered crowns having many branches and leaf layers (oak, ash, gum hickory) are more water efficient than those
Multi-layered white oak

trees with leaf canopies that concentrate leaves in single layers along the outer edge of the crown (beech, sourwood, redbud, magnolia).
Drought-tolerant plants usually have thick bark and leaf waxes (cuticle), efficient stomatal control and extensive root systems.

Finally, some tree species respond to drought by shedding leaves prematurely or wilting. They include black cherry, basswood, beech, birch, buckeye, cottonwood, dogwood, sassafras, sugar maple, sycamore and yellow-poplar (tuliptree). These are not drought-resistant species.

*adapted from an article by Dr. Wayne Clatterbuck, Extension Forestry Specialist, University of Tennessee, Knoxville, TN

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.