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

See Your Perennials Blooming Again

Posted by Hugh on June 4th, 2017

Red Hot Poker (Kniphofia)

Gaillardia ‘Mesa Yellow’

Deadheading is the removal of old spent flowers and stems of many perennials. Many (not all) perennials will respond and bloom a second and even a third time. Deadheading also refreshes the plant’s appearance and reduces or eliminates the threat of seed dispersal. It redirects the plant’s energy away from seed production toward root and vegetative growth.

Deadheading is one more added chore in the growing season. When perennials have finished blooming, remove the entire flower stalk. Depending on species, a perennial may bloom again 2-3 more times.

To reinforce the benefits of deadheading, the perennial bed should be weeded, mulched, fertilized, and watered. Apply a water soluble fertilizer such as Miracle-Gro™ or Schultz™. Clean up the bed, weed, and distribute additional organic mulch. If soil is dry, deeply irrigate the bed for 3 -4 hours (equivalent of 1 ½ inches of rainfall).

Many perennials will not respond to deadheading. Some specific species respond to deadheading, and others not. For most plants prune spent flowers and stems back where they originate near the plant base. New lateral shoots should appear within a few weeks and flowers within 4-5 weeks.

Deadheading Perennials (this list is not complete):

These popular perennials respond to deadheading:

Yarrow (Achillea spp.)

Hollyhock (Alcea rosea)

Columbine (Aquilegia spp.)

Butterfly weed (Asclepias tuberosa)

Hardy begonia (Begonia grandis)

Tickseeds (Coreopsis spp.)

Delphinium (Delphinium spp.)

Cheddar pink (Dianthus gratianopolitanus)

Foxglove (Digitalis spp. and cvs.)

Purple coneflower (Echinacea purpurea)

Queen of the Meadow (Filpendula ulmaria)

Blanket flower (Gaillardia x grandiflora)

Gaura (Gaura lindheimeri)

Geum (Geum spp.)

Sneezeweed (Helenium autumnale)

False sunflower (Heliopsis helianthoides)

Red hot poker (Kniphofia uvaria)

Lavender (Lavandula spp.)

Shasta daisy (Leucanthemum x superbum)

Lupines (Lupinus spp.)

Bee balm (Monarda spp.)

Penstemon (Penstemon barbatus)

Russian sage (Perovskia atriplicifolia)

Meadow phlox (Phlox maculata)

Garden phlox (Phlox paniculata)

Balloon flower (Platycodon grandiflora)

Perennial salvia (Salvia nemorosa)

Pincushion flower (Scabiosa spp.)

Indian pink (Spigelia marilandica)

Stokes’ aster (Stokesia laevis)

Spiderwort (Tradescantia x andersoniana)

Spike speedwell (Veronica spicata)

Culver’s root (Veronicastrum virginicum)

Fall In Love With Haas’ Halo® Hydrangea

Posted by Hugh on June 1st, 2017

Hydrangea ‘Haas Halo’ (photo submitted by Plants Noveau)

Closeup of huge flowers (photo from Plants Noveau)

Anyone walking through your garden will stop to see Haas Halo®) hydrangea (Hydrangea arborescens Haas Halo®). This native smooth hydrangea has intense blue-green, leathery foliage and huge pure white wide lace cap blooms (USDA hardiness zones 3-9). Flowers stand tall on stout sturdy stems. Shrub branching is upright.

This new hydrangea was found by Frederick H. Ray, former horticulture professor at Delaware Valley College in Pennsylvania. Rick selected Haas’ Halo’ from a batch of seedlings given to him by Joan Haas from her garden. Rick chose this plant because it has so many fine traits: strong, sturdy, erect stems, deep bluish-green, glossy foliage, and huge white lace-cap flowers. Flowers measure up to 14 inches across.

Lovely bluish-green foliage is thick and hearty and sets off the huge white lace cap blooms, most of which are fertile. Pollinating insects all cover ‘Haas Halo’. Ray states that very few visited the blooms of ‘White Dome’ growing nearby. The tiny fertile flowers provide nectar for beneficial insects and butterflies.

Smooth hydrangea grows best in average to medium moisture, well-drained soil in part shade although it is very adaptable to different soil types except for very dry. In the mid-South (zones 6 and 7), site it where it primarily receives morning sunlight, and weekly watering if rainfall is sparse. It tolerates more sun the northern part of its range. Blooms on new wood so you may cut it back in late winter to 1-2 feet to keep the shrub looking young and vigorous. Feed with a slow release fertilizer in early winter. Mulch to conserve soil moisture in summer.

Haas Halo is highly drought tolerant after its first year in your garden. It is beautiful planted as a specimen and just as lovely en masse along a woodland edge. Picked flowers also dry well.

Rain Barrels Save Water!

Posted by Hugh on May 29th, 2017

Artwork by Joy Stewart

Rain barrels Connected To Downspouts

The following is a guest blog from Joy Stewart, a good friend who gardens in Bristol, Tennessee. Photos taken at her garden.

Regional droughts and potential water shortages are causing people to turn to a centuries old practice of collecting rain as an alternative source of water. By collecting rainwater from your home’s roof, you have an additional supply that doesn’t tax the groundwater or shoot up your water bill.

Better yet, rainwater is oxygenated, non-chlorinated and warmer than tap water; all of these factors make it a superior source of water for your garden plants. Rain barrels are one of the simplest, cheapest means of providing water for the plants in your yard.

You will be surprised at the amount of water generated by even a brief downpour. One inch of rain on one square foot of ground surface produces .623 gallons of water. That means if you live in a smaller 1,000 square foot home and have a downspout from collects water from one quarter of the roof area, one-half inch of rain will give you almost 100 gallons of water for your rain barrel.

Rain barrels are available commercially, ranging from 50 up to 850 gallons and costing between $70 and $600. However, you can easily make your own barrel for as low as $30, depending on where you obtain your barrel. With a little searching, you can often find a used 55-gallon barrel, one formerly used to ship soda syrup, cooking oil, soap for car washes and even jalapeno peppers (although that smell is hard to remove) for about $10.

All other parts for construction are available at your local home construction supplier. A wide range of “how-to” instructions for construction and installation are available on the Internet. Once built, you can even use a good quality house paint to decorate them.

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.