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

New PG Hydrangeas Excel In Performance

Posted by Hugh on August 10th, 2016

H. paniculata ‘Little Lime’

Hydrangea ‘Quick Fire’

Panicle, PeeGee or PG hydrangeas (Hydrangea panculata) brighten up the July and August garden landscape. They’re native to China and Japan.

They grow and bloom almost anywhere in the U.S. (USDA hardiness zones 3 – 8). Unlike mophead hydrangeas (H. macrophylla), that often fail in full day sun, PGs excel in 6 hours or more of sun.

PG hydrangeas are vigorous growers with upright branching and coarse textured deciduous foliage. Depending on variety, shrubs grow 3-15 feet (some to 25 feet) tall. Multi-branched shoots are clothe with dark green, oval shaped leaves and are topped with upright, sharply-pointed, conical, 6-8 inch long terminal flower panicles. Flowers may be a mix of both fertile and sterile florets and bloom from mid-summer into fall. PG hydrangeas are pruned any time from late fall to mid-spring. They may also be trained into a tree form.

Most gardeners today know PGs by the best selling cultivar ‘Limelight’ which has become the standard for excellence. It grows 6-10 feet tall (depending on amount of annual pruning provided); heavy with 6-8 inch, conical shaped, terminal flower panicles; branching is very upright.

‘Limelight’ at NC Arboretum, Asheville, NC

Three of “new” best paniculatas are:

‘Little Lime’ – grows 5-7 feet tall; large, tightly packed, lime-white flowers that turn shades of pink where summers are cool.

‘Quickfire’ – grow 6-8 feet tall and equally wide; blooms are white, become pink after a few weeks, and finish rosy-pink.

Bobo™ – this Belgium introduction is a very compact size that is ideal size-wise in small gardens and patio containers; large white loose blooms midsummer to fall.

Bacterial wilt, leaf spot, rust, and mildew diseases and aphids and mites are occasional disease and insect problems. Poor site selection often enhances problems with diseases and pests.

Garden Phlox – Select Mildew Resistant Varieties

Posted by Hugh on August 7th, 2016

Garden phlox (bicolor)

Phlox ‘David’

Garden phlox (Phlox paniculata), aka summer phlox, is native from New York to Iowa south to Georgia, Mississippi and Arkansas (USDA hardiness zones 4 to 8(9)). They are valued for their long beautiful floral display and fragrance. In the wild phlox grow it in moist, rich open woodlands, alluvial soils along streams and rich garden soils.

The right location is an absolute when growing garden phlox. Phlox prefer an compost-rich, moist, moderately acidic, well-drained soil. Best flowering on sturdy healthy plants is in full sun. Space plants adequately for good air circulation to prevent or reduce powdery mildew problems. Phlox are intolerant of dry soils and summer dry spells. Avoid overhead watering and trickle irrigation; mulching helps to cool soil and maintain soil moisture. Remove faded flower panicles to prolong bloom period and to prevent unwanted self-seeding (cultivars generally do not come true from seed).

Garden phlox are clump growers and grow 2-4 feet tall and 2-3 feet wide on sturdy stems. The dark green lance-shaped leaves are 4-6 inches long and prominently veined. Dome shaped flower clusters are densely packed with a hundred or more 1 inch wide tubular florets. Each individual floret has a long corolla tube and five flat petal-like lobes. Color choices include white, lavender, pink, rose, red and bi-colors. Butterflies and hummingbirds swarm around the fragrant flowers; deer usually stay away.

Divide clumps every 3-4 years to maintain plant vigor.

Phlox is not always an easy plant to grow. Powdery mildew and occasional spider mites can be troublesome, particularly in the southeastern U.S. Do your homework when selecting the cultivars to plant in your garden. Check for trial garden evaluations at state agricultural university. A cultivar rated as resistant in powdery mildew in Chicago may not be in Philadelphia, Atlanta, or Dallas. In a 1999-2001 North Carolina State University Trial in Mills River, no varieties proved to be completely powdery mildew resistant. However, these cultivars exhibit a high degree of disease resistance: ‘David,’ ‘Delta Snow,’ ‘ Natascha,’ ‘Robert Poore,’ ‘Speed Limit 45’ and the species Phlox caroliniana.

Some comments from Mt. Cuba phlox trials (2015-17) in Delaware have been added. This garden blog will be updated in future.

Powdery mildew resistant cultivars to try:

‘David’ – pure white tubular florets; 3-4 feet tall and 2-3 feet wide; floral display not impressive in Mt. Cuba trial.

‘Delta Snow’ – snowy white tubular / purple eye florets; 2-3 feet tall and wide; plants became floppy in midsummer in Mt. Cuba trial.

Flame™ Pink – fuchsia pink /darker pink eye florets; compact 15-18 inches tall and wide; some leaf spotting in late summer.

‘Katherine’ – dense, blue-lilac / white center florets; 2-3 feet tall and wide; spider mites problem in Mt. Cuba trial.

‘Minnie Pearl’ – white florets; 20 inch tall and wide; repeat blooming; floppy plant habit in late summer.

‘Robert Poore’ – rich lavender purple florets; 4-5 feet tall and 2-3 feet wide; spider mites problem in Mt. Cuba trial..

‘Shortwood’ – pink / dark pink eye florets; 42-48 inches tall and 24-30 inches wide.

‘Volcano Purple’ – lavender/purple / white eye florets; very compact 12-20 inches tall and 18-24 inches wide.

Joe Pye Weed Is No Longer A “Weed”

Posted by Hugh on August 4th, 2016

Joy Pye (Eupatorium) and Goldenrod (Solidago)

Eupatorium dubium ‘Baby Joe’ at Univ. of Tennessee Gardens, Knoxville

U.S. native Joe Pye (Eupatorium spp.), formerly “Joe Pye Weed”, has been tamed. Modern day selections grow more compact compared to 8+ feet tall wildlings that inhabit fields across eastern North America (USDA hardiness zones 4-8). Huge, terminal, domed, compound flower heads measure 12-18 inches across (depending on cultivar) and make excellent cut flowers.

The most popular cultivar is ‘Gateway’ (E. purpureum ssp. maculatum ‘Gateway’) which produces magnificent domes of mauve pink flower clusters that sit atop sturdy purple stems. ‘Gateway’ typically stands 4-5 feet tall and erect in clumps and with dense thick inflorescences. Dark green 8-inch long lance-shaped leaves are coarsely-serrated and arranged in whorls of 3-4 on sturdy, wine-red stems.

Common Forms of Joe Pye:

Hollow stemmed Joe Pye (E. fistulosum) is a robust, upright perennial with hollow purple stems accented by huge, rounded, tight clusters of pink or purplish-mauve flowers.

‘Baby Joe’ Joe Pye (E. dubium) – mauve purple flowers appear on 3 to 4 foot tall plants from July to September (zones 3 to 9).

E. rugosa ‘Chocolate’ leaves with deep shiny purple stems makes a wonderful contrast to explosions of white flowers along with numerous kinds of butterflies in September and October.

‘Phantom’ is a new hybrid cultivar of E. maculatum ‘Atropurpureum’ and E. rugosum. Phantom is a very short growing Joe-Pye, just under 3 feet tall. The dome-shaped lavender head flowers appear most of August. The whorled foliage is dark green on sturdy stems.

Joe Pye thrives in moist fertile soils along edges of ponds and streams. Plant is highly drought tolerant, although leaf edges often scorch in dry summers. It is disease and pest resistant and deer and rabbits stay away. Many kinds of butterflies, bees and other pollinators visit the florets. Seedheads persist well into winter and provide food for foraging birds. Keep poisonous leaves of Joe Pye away from grazing animals. Shortened cultivars are great stand-alone flowering perennials and serve as bold background plants.

Herbal folklore: Joe Pye (or Jopi) is named for a traveling Native American medicine man who lived in New England around the American Revolution era. He sold various herbal remedies to the colonists. Historically, Joe Pye weed was utilized to treat typhoid fever.

August Is Also An Important Planting Month

Posted by Hugh on August 1st, 2016

Cabbages heading at Dallas Arboretum in early January

‘Wirosa Savoy’ Cabbage at Atlanta Botanical Garden in October

“A” starts the alphabet. To most gardeners April starts out the spring planting season. Temperatures are in the comfortable 70°F degree range. Four months later in August, temperatures outside are sweltering. Many of us call them the hot humid “dog days” of August. Dogs and gardeners are suffering alike.

However, August is also a great time to plant flowers and vegetables. Visit the local garden center and buy large 6 inch size annuals which are often “on sale”. Buy fresh plants and not the potbound, worn out leftover annuals which the store did not sell in the spring. Some of the best to plant in August include petunias, calibrachoas, (million bells), geraniums, snapdragons, diascias, and marigolds. Pansy seed must be started in a cool basement environment under “gro-lights”.

In the mid-South region (USDA hardiness zones 6 and 7), September and October weather is usually great for flowers planted in mid-summer. When setting out plants, water them daily during week one, then every 2-3 days in the 2nd and 3rd weeks. Then, water plants as needed. These annuals are demonstrate exceptional cold tolerance, unfazed by mid-20°F nights in fall.

Many vegetables may be established in August. Cabbage, broccoli, cauliflower, lettuce, carrots, beets, and green beans need 60-70 days above freezing to produce a good crop. Cole crops such as broccoli, cauliflower, brussel sprouts, and cabbage are easiest to produce in the late summer into autumn than those started in spring. Spring plants often bolt (go to seed) in the spring as temperatures heat up. Cole crops welcome the cool days of autumn.

In addition, pest activity diminishes with cooler temps. Some pesticide spraying may be needed, although plants can be protected with a cheesecloth or Remay fabric cover. Use a safe bio-insecticide like Dipel or Bt (Bacillus thuringiensis kurstaki) against wormy caterpillar pests.

Chanticleer Garden – A Garden For Ideas

Posted by Hugh on July 30th, 2016

Fall Scene at Chanticleer

Tropicals In Terrace Gardens

Chanticleer Garden is an estate and botanical gardens, that bills itself as a “pleasure garden”. Chanticleer is “a garden for ideas”. The property is located at 786 Church Road in Wayne Pennsylvania, approximately 30 minutes of Philadelphia. Chanticleer celebrated its 100 year centennial in 2013 as the Rosengarten estate and 20th year as a public garden. The entrance gate is crested with carved stone roosters (chanticleers in French). The house and grounds have been listed on the National Register of Historic Places since 1984.

Chanticleer is a destination garden to enjoy, learn, and relax. Gather lots of ideas to take home to your property. The garden has evolved greatly since the death of the owner in 1990. As the home of the Rosengartens, Chanticleer is green and beautiful with impressive trees and lawns. Most of the floral and garden development you see today has occurred since 1990, designed by Chanticleer staff and consultants.

Seven horticulturists are assigned to the seven areas of the garden; they design, plant, and maintain their garden area. The Teacup Garden and Chanticleer Terraces feature seasonal plants and bold-textured tropical and subtropical plants. The latter areas change greatly from year to year. In the fall non-hardy plants are dug up and overwintered in greenhouses and basements.

The Tennis Court, Ruin, Gravel Garden, and Pond Garden focus on hardy perennials. The Tennis Court is a floral and foliar delight. The Ruin is a folly, built on the foundation of Adolph Rosengarten, Jr.’s home. It is meant to look as if the house fell into disrepair. The Gravel Garden is hot and dry, a touch of the Mediterranean in Pennsylvania. The Pond area is nothing short of a floral masterpiece.

Asian Woods and Bell’s Woodland are shady areas that feature native plants of eastern Asia and eastern North America. The cut flower and vegetable gardens produce flowers for arrangements and food for the restaurant and staff tables. Surplus goes to a local shelter.

Chanticleer gardeners will answer your questions about our 5,000+ plants. Plant lists and photographs are posted in on-site handmade mailboxes. The information is also available online.

The Chanticleer Foundation owns 47 acres, 35 of which are now open to the public. The main walking path is just under a mile long. Relax, read, sketch, converse, meditate. Picnic tables, benches and Adirondack chairs are spotted around the property for leisure and to catch views of plants and wildlife.

Chanticleer is open Wednesday through Sunday, April through October, from 10 a.m.to 5 p.m. Admission fee: $10 (2014). Plan a minimum 2-3 hour visit.

Woodland Respite

Need To Deadhead Perennials

Posted by Hugh on July 28th, 2016

Veronica ‘Royal Candles’

Blanket flower (Gaillardia) re-blooms after deadheading

Deadheading is the practice of removing spent blossoms to stimulate re-blooming. It also refreshes the plant’s appearance, and lessens the threat of seed dispersal. It redirects the plant’s energy from seed production to root and shoot growth.

Deadheading is an extra chore throughout the growing season. When the plant (perennial or annual) has stopped blooming or its appearance starts to decline, remove the entire flower stalk. Depending on species, a perennial may bloom again 2 -3 more times. Weather and soil moisture and soil fertility are also key factors.

After deadheading apply a water-soluble fertilizer such as Miracle-Gro™ or Schultz™. This is good time to clean up the bed, weed, and add organic mulch. If the soil is dry, irrigate the bed deeply with 3 – 4 hours of overhead irrigation (equivalent of 1 ½ inches of rainfall).

Many perennials do not respond to deadheading. Like other types of pruning, deadheading is plant species specific. It can be difficult to group plants (or people) into categories. For most plants remove spent flowers and stems back where they originate near the plant base. New lateral shoots should appear within a few weeks and blooms 3-5 weeks later.

Deadheading Some 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)

Canna lily (Canna spp.)

Tickseed (Coreopsis spp.)

Cheddar pink (Dianthus gratianopolitanus)

Delphinium (Delphinium spp.)

Foxglove (Digitalis spp. and cvs.)

Purple coneflower (Echinacea purpurea)

Blanket flower (Gaillardia x grandiflora)

Gaura (Gaura lindheimeri)

Geum (Geum spp.)

Sneezeweed (Helenium autumnale)

False sunflower (Heliopsis helianthoides)

Lavender (Lavandula spp.)

Shasta daisy (Leucanthemum x superbum)

Lupine (Lupinus spp.)

Bee balm (Monarda spp.)

Penstemon (Penstemon barbatus)

Garden phlox (Phlox paniculata)

Perennial salvia (Salvia nemorosa)

Pincushion flower (Scabiosa spp.)

Indian pink (Spigelia marilandica)

Stokes’ aster (Stokesia laevis)

Spiderwort (Tradescantia x andersoniana)

Spike speedwells (Veronica spicata)

Culver’s root (Veronicastrum virginicum)

Time to deadhead Helenium

Long-Blooming Tennessee Coneflower

Posted by Hugh on July 24th, 2016

Echinacea tennessiensis

TN coneflower at Butterfly Arboretum in Jonesborough, TN

Native to a two-county area of mid-Tennessee, Tennessee coneflower (Echinacea tennessiensis) is a popular favorite among gardeners across the U.S. because of its long blooming season. It has also spawned a few hybrid selections. The pale pink, flat-topped flowers with green and burgundy centers (cones) follow the tract of the sun across the sky.

From July thru September Tennessee coneflower has short, slightly upturned petals that are 2 to 3 inch across. Petals are not reflexed backwards as those of purple coneflower (E. purpureum).

Tennessee coneflower prefers moist well-drained soils until well-established. It is an ideal choice for hot sites and in rocky shallow soils. The species is best suited in full sun, but can cope with partial shade.

Tennessee coneflowers have no serious insect or disease problems. Japanese beetle, powdery mildew and leaf spot are occasional problems. They do not benefit from additional fertility which may actually weaken stems. Flowers attract many species of birds and butterflies. Deer do not normally feed on coneflowers.

Divide clumps when they become overcrowded every 4 to 5 years. Plants re-bloom without deadheading. Prompt removal of spent flowers improves general appearance. Group several plants together in a perennial border, meadow, or wildflower garden. Compact forms grow well in containers for a long bloom season.

Hybrid cultivars:

‘Rocky Top’ is a compost grower with pastel pink on 2 to 3 feet tall and 1 foot wide plants.

Pixie Meadowbrite™ is another compact form medium pink flowers. A true dwarf, each plant grows to 18 inches tall and 20 to 24 inches wide.

Once listed as endangered, Tennessee coneflower has now been de-listed and is easy to find in commerce.

Spider Flowers Excel In Summer’s Heat And Humidity

Posted by Hugh on July 21st, 2016

Spider flower (Cleome) at Dallas Arboretum in Texas

Cleome ‘Senorita Mi Amor’ at Univ. of Tennessee Gardens, Knoxville, TN

Spider flowers (Cleome x hybrida) are top performing summer flowering annuals. Each year plant breeders introduce compact varieties to beautify flower beds and container gardens. Select among vegetative and seed produced types.

Spider flowers ask for weekly watering and full day sunlight (best) to achieve maximum blooming potential. They will grow in a partially shaded beds but bloom less and the plants tend to stretch.

Cleomes grow in average soil that is well-drained. Amending the soil with compost at planting and mulching are highly recommended to keep them highly floriferous. Rated as moderately drought tolerant, spider flowers prosper under weekly irrigation. Before planting work in lots of compost into garden soil or container media; broadcast a slow release fertilizer over the entire bed.

By mid-summer heavy feeding plants, particularly those in containers, become nutritionally deficient. Bottom leaves are first to turn yellow and bloom count becomes more sparse. Summer- feed container plants twice monthly with a water soluble fertilizer such as Miracle-Gro®, Peters®, or Schultz® at label rates.

Spider flowers are highly disease and pest resistant. Low compact forms require no staking compared to old-fashioned tall varieties that your grandmother used to grow.

Leading Cleome hybrids are:

Cleome Clio Magenta – 18 – 36 inches tall and 12 – 24 inches spread violet spider-like flowers with pink overtones.

Senorita Rosalita – 24 – 48 inches tall and 18 – 24 inches wide; do not self seed, keeps its lower foliage all season long; not prickly.

Sparkler series -reach 3 1/2 – 4 feet tall; plants are vigorous, and bloom heavily from spring to early fall; choice of white, blush and lavender.

Do Not Call Them “Weeds” Any Longer

Posted by Hugh on July 18th, 2016

‘Gateway’ Joe Pye in East Tennessee Garden

Helenium ‘Moerheim Beauty’

Butterfly weed (Asclepias)

Some plants deserve more respect. Over the years several U.S. native species have been tamed or domesticated. Yet, they retain their common name “weed”. Four popular former “weeds” are:

butterfly weed (Asclepias tuberosa)
ironweed (Vernonia lettermannii ‘Iron Butterfly’),
sneezeweed (Helenium autumnale), and
Joe-Pye weed (Eupatorium spp.).

Butterfly weed (Asclepias tuberosa) is a tuberous rooted long-lived perennial found in dry/rocky open woods, glades, prairies, fields and roadsides across the Eastern and Southern U.S. Plants are slow to establish and may take 2-3 years to produce flowers. Mature plants may freely self-seed in the landscape if seed pods are not removed prior to splitting open. Butterfly weed does not transplant well due to its deep taproot, and is probably best left undisturbed. It typically grows in a clump to 1-3 feet tall and features clusters (umbels) of bright orange to yellow-orange flowers atop upright to reclining, hairy stems with narrow, lance-shaped leaves.

Joe-Pye (Eupatorium spp.) has 4 to 5 feet select varieties which grow much shorter than the wild species. Sturdy stems are clothed with whorls of green leaves and topped with dome-shaped heads of lavender to pink flowers in mid-summer . Leading cultivars are: ‘Gateway’ -tiny, dusky rose-pink flowers form a huge, terminal, domed, compound inflorescence (12-18 inch diameter) in mid-summer to early fall, ‘Chocolate’, and ‘Little Joe’.

Ironweed (Vernonia lettermannii) is a compact, well-branched and vigorous plant. In late summer its vivid purple flowers are covered with butterflies and other pollinators. Ironweed is found growing in poor rocky soils, tolerates long periods of submersion (flooding), yet it is highly tolerant of hot dry sites. Cultivar ‘Iron Butterfly’ is a low mounding perennial form with narrow fine textured foliage. Plants are 2-3 feet tall and equal in spread. Sturdy plants are strongly anchored by a sturdy taproot. Branch terminals are covered by small clusters of deep purple disc florets in late summer.

Sneezeweed (Helenium autumnale) is an erect, clump-forming perennial which typically grows 2-3 feet tall (sometimes to 4 feet) on sturdy stems. It has a lengthy bloom season from summer into to early fall. Daisy-like 2 inch wide flowers have wedge-shaped, coppery-red (or yellow) rays that are notched at the tip and prominent, dark dome-like center disks. Leading cultivars are ‘Moerheim Beauty’.

All four perennials are favorite nectar plant of bees and butterflies, particularly the Monarch butterfly larvae. They prefer sunny sites with average to dry soils. Grow in average, medium to wet, well-drained soil in full sun. Over-fertilization may force plants to grow too tall. Although not required, three species, not butterfly weed (Asclepias) may be cut back in early July (at least 6 weeks before normal flowering) to reduce plant height and encourage branching, thus increasing bloom count, healthier foliage, and less need for support. Remove spent flowers to stimulate additional bloom. Divide clumps every three years to maintain vigor. They are disease and pest resistant and is not bothered by deer or other herbivores.

Late Summer Planting of Vegetables

Posted by Hugh on July 15th, 2016

Two Varieties of Cabbage for the Late Summer Garden

Cauliflower seedlings for sale at local Garden Center

Mid to late summer is the second season for planting many (not all) kinds of vegetables and herbs in many parts of the U.S. There is still 3 months or more of great growing weather ahead to harvest veggies planted now. You’ll enjoy great harvests for the Thanksgiving and perhaps the Christmas/winter holiday table (USDA zones 5-7).

Start with leafy greens for salads or garnish such as lettuce, pak choi, chard, and parsley. Carrots, beets, peas, green onions, spinach, radish, and some brassicas (cabbage, broccoli, cauliflower, and turnips) are good picks for the fall garden. Long season veggies such as tomatoes, cucurbits (cucumber, pumpkins, squash, and others), and sweet corn are not included.

Diseases, insects, and weeds are less problems. Crops like cabbage, cauliflower, and broccoli can be store outdoors in the garden row through most of the winter without them going to seed (bolting) or developing a bitter taste. Pick them as you need them for the dinner table. Transplants of lettuce, cabbage, broccoli, cauliflower, and others are available at local garden centers starting in August, depending on locality.

In summer start seedlings in pots, flats, or other containers in the cool home basement under gro-lights or in an outdoor cold frame; or directly sow seeds directly into the garden in dappled sun or light shade, but not in direct sun.

Set your new veggie transplants in a moist garden or raised bed, preferably around twilight when it is cooling off. In the mid-South protect new transplant seedlings under row covers or shade cloth for several days to acclimate them to sun and heat. Light sprinkling (spritzing) seedlings 2-3 times daily also cools seedlings.

Seedlings should adapt to outdoor beds within a week. Keep them adequately watered and fertilized. In USDA zones 8, 9, and 10, some fall-planted crops are harvested all winter long.