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

‘Gateway’ Joe-Pye Fits Most Gardens

Posted by Hugh on August 22nd, 2011

'Gateway' Joe-Pye

On hot clammy August days, towering 6-8 feet in height, there is Joe-Pye* weed (Eupatorium purpureum) to enjoy. It is visually hard to miss when driving along rural roads in the Southern Appalachian region (USDA zones 6 and 7). Joe-Pye’s flowering sends me a timely message that autumn is only six weeks away.

For gardens the cultivar ‘Gateway” (E. purpureum spp. maculatum ‘Gateway’) is a better fit, more compact at 4-5 feet tall and 3-4 feet wide. Its enormous compound inflorescences measures 12-18 inches in diameter. From late summer into fall the dusky pink flowers invite numerous butterflies and other insects into your garden and make great cut flowers.

Gateway’s upright form and stout branches require no staking. The large narrow dark green leaves are 5-8 inches long and coarsely-serrated, arranged in whorls around the purple and white splotched stems. The mighty architectural seed heads persist well through the winter months.

Joe-Pye, aka “Queen of the Meadow”, demands full to partial (6-hours minimum) sunlight. Joe-Pye is a wetland native and thrives in moist, compost-rich garden soil. Fertilizing this long-lived perennial is not necessary. Plants emerge in late spring and grow very rapidly. Situate in the rear of flower borders due to its plant size and coarse foliage texture. Joe-Pye has no serious diseases or insects and is deer resistant.

* According to forklore, the plant is named for Joe Pye (or Jopi), who was a traveling Native American medicine man. He lived in New England around the late 1700s and sold various herbal remedies to the colonists to treat kidney and urinary problems and typhoid fever. Leaves were also dried and burned as incense to repel flies.

Summer Leaf Drop From Trees

Posted by Hugh on August 20th, 2011

Leaf shedding from tulip poplar

It’s late summer in the Southern Appalachian region (USDA zones 6 and 7). Outdoor temperatures continue to hit 90°F almost daily, and weekly precipitation is low. Over the past 3-4 weeks leaves have been dropping prematurely from landscape trees.

Tulip poplar (Liriodendron tulipifera), river birch (Betula nigra), willow (Salix spp.), sycamore (Platanus x acerifolia), elm (Ulmus spp.), hackberry (Celtis spp.) and redbud (Cercis canadensis) appear the worse offenders.

What these trees have in common, other than yellow fall color, is that growth is continuous from early spring thru late summer. Trees produce new leaves as long as air temperatures and soil moisture are favorable. Such trees abort excess foliage when environmental conditions become stressful.

Another way of stating: these species tend to overachieve, producing more leaves than they can support as environmental conditions turn negative. Under typical hot dry summer weather, they conserve through a dry patch by shedding leaves. The older interior foliage is typically the first to abort. Most summers all seven listed species lose leaves prematurely.

Bottom line: prematurely shedding leaves is very normal for these and some other landscape trees. Deep irrigating of trees reduces leaf loss, but is generally unnecessary. Leaf loss is a natural phenomena and is not detrimental.

The Challenge and Reward of Harlequin Glorybower

Posted by Hugh on August 17th, 2011

Harlequin glorybower in mid-August

Harlequin Glorybower (Clerodendron trichotomum) is a rambling 15 foot tall shrub, and can be easily shaped into a multi-stemmed 10-12 foot small tree. Glorybower shines in the late summer and early fall landscape. Its sweetly scented, very showy flowers attract the attention of gardeners as well as hummingbirds and butterflies.

Glorybower reaches its northern- most hardiness limit here in the Southern Appalachian region (USDA zones 6-b and 7). Some winters do not treat glorybower kindly. Significant reconstruction is needed. Moderate pruning in late winter repairs most ills with fast growing glorybower looking great by summer.

Flowers are arranged in wide 6 – 9 inch clusters, comprised of individual white 1 ½ inch blooms and are borne on current season’s wood. Next up in mid-September are the metallic looking topaz colored fruits with beet red calyxes which give quite a show.

Foliage texture is bold with broad 4 to 9 inch long dark green leaves providing cooling shade to a nearby deck or patio. Its pale yellow autumnal leaf color contributes little. Glorybower is relatively disease and insect free.

Glorybower grows in a moist well-drained average soil and in full to partial (minimum 6- hours) sunlight. A 2-year old established tree is only moderately drought tolerance and requires irrigation during long dry spells.

This under-utilized native of Japan and China is sold principally by internet nursery vendors.

Old-Timey ‘Royal Standard’ Hosta Still Rules

Posted by Hugh on August 14th, 2011

Hosta 'Royal Standard' at Kingwood Center

Kingwood Center is a wonderful public garden in Mansfield, Ohio with several top notch beds of hostas. One glorious bed of ‘Royal Standard’ hosta blooms their heads off from mid-August into September. With over 35,000 registered hostas available, why look back at this vintage variety.

Royal Standard was patented and introduced in 1965 by Wayside Gardens and still remains popular. Its 4 – 5 inch long green leaves are ordinary compared to modern day hosta cultivars. A multi-division clump develops foliage around 18 inches tall and spreading to 4 feet across. White trumpet shaped flowers rise 24 inches tall on leafy scapes in August and are pleasantly fragrant.

Royal Standard grows in a wide array of garden soils, yet it excels in compost rich soils. Two-year established Royal Standard demonstrates good summer heat and drought tolerance in the Southern Appalachian region (USDA zones 6 and 7).

Morning sunlight followed by light afternoon shade is preferred, but I have seen a terrific bed planted in a gas station island under full day sun, assumedly with regular irrigation.

Plant foliage dies down in the winter. Clumps are easy to divide either in early fall or late spring. Slugs are the principal major pest problem of many hosta cultivar, including ‘Royal Standard’.

‘Kim’s Knee High’ Coneflower For Small Gardens

Posted by Hugh on August 11th, 2011

'Kim's Knee High' coneflower

We are in the midst of an Echinacea revolution. Purple coneflower (Echinacea purpurea) is a popular 5-6 foot tall native perennial commonly planted in meadow and butterfly gardens. Kim Hawkes, former owner of Niche Gardens Nursery in Chapel Hill, N.C. introduced compact growing ‘Kim’s Knee High’ a decade ago. It is still one of the finest cultivars.

‘Kim’s Knee High’ fits into most small gardens at 2-3 feet in height and 1-2 feet in spread. Coneflower grows in average well-drained soil and in full to partial (minimum of 6 hours) sunlight.

‘Kim’s Knee High’ is low maintenance. It exhibits moderate heat and drought tolerance after one year’s establishment in the garden. Coneflower thrives on late winter feeding. Clumps should be divided every 3-4 years.

The 3 ½ inch rose pink ray petalled flowers are slightly reflexed, and surround a russet-orange cone center. Coneflower blooms from late June through late August in the Southern Appalachian region (USDA zones 6 and7). Deadheading old spent blooms extends flowering time through first October frost.

Coneflowers attract numerous butterflies and bees, and seeds are a major winter food source for many species of birds, particularly finches and hummingbirds. Seeds self-sow and become nuisance weeds. Remove all old growth in the early fall to avoid the seed load or wait until late winter in order to feed the birds.

Pest problems are minimal if plants are not overcrowded. Coneflowers are deer resistant.

Explode Your Plant Roots

Posted by Hugh on August 9th, 2011

Dead rootball

One of my gardening frustrations is watching a new plant linger and not grow. I dig a proper hole, deep and wide enough. I pour gallons of water on the plant to keep it alive during a dry hot summer. Four months later, the plant is the same size as last spring or it finally dies!

What went wrong? I dig it up. What I see is a root system which did not grow into good soil in the hole (photo). A friend asks, “did I explode the roots”. He has seen this problem many times at his nursery/ landscape business. He took action. His objective: “no plant, annual, perennial, shrub or tree, goes into a container or planting hole without exploding its root ball.

He uses a brick to bust apart the soil (media) around the root ball. His objective is two-fold: first, to break apart circling or potentially girdling roots; and secondly, to shake off as much soil that the plant is growing in. His goal is to coax new roots to venture out into the surrounding soil in the hole. Some landscape gardeners use a butcher’s knife to slice apart the root ball. He uses a brick.

When purchasing plants from late spring thru fall, assume that the nursery/greenhouse plants are leftovers that did not sell. Plants on sale likely need to be transplanted. The grower/garden center manager does not want to expend time and material to repot it. The grower is passing that chore along to you at a discount price.

‘Morning Calm’ Trumpet Vine

Posted by Hugh on August 5th, 2011

Campsis grandifolia 'Morning Calm'

Our native trumpet vine, aka trumpet creeper (Campis radicans), may instill fear in gardeners. A wild vine may climb a utility pole, 30- 40 feet in one year. The late horticulturist Dr. J. C. Raulston at NC State University in Raleigh recommended its tamer Chinese cousin (C. grandiflora) and the cultivar ‘Morning Calm’.

Trumpetvine climbs and supports itself by strong rootlets or “holdfasts”. Start one on a cedar pole, tying the shoots loosely with cotton cord. Within one year the vine bonds solidly to a wooden trellis, wire fence, or a coarse surfaced brick wall. The trellis should be structurally strong to support the vine’s incredible growth and weight.

The 7-9 leaflet glossy compound leaves are 6-12 inches in length. The vine blooms on new growth and the trumpet-like flowers are clustered in numbers from 6-12, sometimes more. The dark apricot colored flower (corolla) appears from late June thru mid- August. Each trumpet flower measures 3 inches in length when fully open.

Trumpet vine grows in average garden soil, is very heat and drought tolerant, and has few enemies. The vine should be pruned aggressively in late winter. Trumpet vine benefits from liquid feeding with Miracle-Gro™ or an equivalent fertilizer containing minor nutrients.

‘Morning Calm’ attracts numerous butterflies and hummingbirds and is often falsely marketed as “hummingbird vine”.

Hibiscus Sawfly Devastates Plant Foliage

Posted by Hugh on August 3rd, 2011

Hibiscus Sawfly Damage

The hibiscus (mallow) sawfly is a devastating pest of hibiscus (Hibiscus moscheutos) and hollyhock (Alcea rosea). The adult sawflies are small, barely a quarter inch long. They are mostly black, except for a yellowish brown spot on their thorax, and their smoky wings. The pale green larvae mature to 1/2 inch in length.

The larvae turn hibiscus foliage into lacy skeletons. The adult females lay eggs in the upper surfaces of leaves and, at first, produce blister-like bumps. The larvae hatch, move to the underside of the leaf, and begin to feed voraciously. Mature larvae pupate at the base of the plant. Hibiscus sawfly develops up to six generations from mid-spring until frost.

Select one of two control strategies:

foliar sprays of any one of the following insecticides: acephate, pyrethrins, synthetic pyrethroids (such as bifenthrin, permethrin, and cyfluthrin), and spinosad; spray every 7 -10 days or when leaf damage is observed.
soil drench with any insecticide product containing imidacloprid; only one application offers season long control.

Sawfly resistant cultivars may be in the future. Currently, there is no resistance in H. moscheutos, but some in swamp rose mallow (H. grandiflora), and in scarlet rose mallow (H. coccineus).

Related: Blog on ‘Fireball’ hibiscus published June 18, 2011

A Canna Lily Revival

Posted by Hugh on July 30th, 2011

'Bengal Tiger' Canna at Kingwood Center, Mansfield, Ohio

'Australia' Canna at Kingwood Center, Mansfield, Ohio

Depending on where you garden, Canna lily (Canna spp.) is a tropical-looking, herbaceous annual or perennial. Its colorful foliage and long blooming time leaves a huge visual impact. Canna is not reliably winter hardy in the Southern Appalachian region (USDA hardiness zones 6 and 7). Canna relishes moist soils. Container grown plants thrive submerged in a water garden.

Leaves wrap spirally around the main stem(s). Most cultivars have emerald-green foliage, either a waxy (glaucous) or dull (matted) leaf surface. Some exhibit colorful andvariegated foliage. New canna leaves unfurl at night.

Canna flowers from midsummer up to first frost. Cultivar heights range from 5 to 15 feet (and more), depending on the cultivar and its care. Removal of spent flowers stimulates formation of new floral heads. Flower choices range from oft-white, yellow, orange, red, and a mosaic of many colors. Canna flowers are visited by bees, hummingbirds, and butterflies.

Three favorites in the colorful foliage category are ‘Australia’ (purple leaf, red flower); ‘Bengal Tiger’ aka ‘Pretoria’ (yellow/green striped leaf, orange flower); ‘Tropicana’ aka ‘Phaison’ (green, red, purple, gold striped leaf, salmon orange flower).

A serious problem of cannas is virus diseases, which cause leaves to distort or mar the colorful foliage. Leaf roller insects may also build up and become a serious pest in some gardens.

In late fall canna rhizomes are lifted from garden beds and stored in dry peat moss above freezing over winter.

More about “Winter Care of Tropicals” in a late October blog.

Native Plumleaf Azalea Blooms In The Heat Of Summer

Posted by Hugh on July 28th, 2011

: Plumleaf Azalea (Rhododendron prunifolium)

From my garden here is a look today (July 28th) at plumleaf azalea (Rhododendron prunifolium). Plumleaf is an Alabama native, and its orangey red flowers has been growing in my east Tennessee garden for the past 15+ years.

It is hardy to zone 5-b (- 15°F) which includes most of the mid-Atlantic and southern New England states. Plumleaf handles Southern clay and mid-6.0 pH soils quite well. Flowering time is nearly two weeks long, mostly in morning sunlight. A red and pinkish-red flowering selections are now available.

Annual care is minimal, including little pruning, nutrition and watering chores. There have been no disease or insect problems over the years. I admit to irrigating established shrubs during severe dry spells.

Plumleaf azalea may be purchased from most native plant vendors in the Southeastern U.S., several within reasonably close drive of your home or on-line. I purchased my plant, seems like a long time ago, at Callaway Gardens in Pine Mountain, GA .