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

The Best of the Coralbells- So Far!

Posted by Hugh on April 11th, 2010

Photo: Heuchera villosa natural purple leaved form

The Heuchera x villosa coralbell revolution has been upon us for nearly a decade. Many new hybrid coralbells have been introduced. This southern Appalachian native coralbell exhibits exceptional heat, humidity and drought tolerance. You find hairy alumroot growing in dry shade and partially sunny areas.

This is a report card on the hairy alumroot hybrid cultivars. Listening to other gardeners and observing their performance in my garden, ‘Mocha’ (dark coffee colored foliage), ‘Citronelle’ (bright yellow) and ‘Caramel’ (dark peachy yellow), have earned my highest recommendations among the colorful large foliage types.

I continue to watch ‘Tiramisu’, with its medium-sized, yellow with red splotched leaves. It has yet to impress me. However, gardening friends urge me to wait another year “before throwing in the trowel”.

I also grow the pale green leaf, mid-summer blooming ‘Autumn Bride’. A cloud of tiny white flowers hovers over the plant foliage in August. I see it used en masse as a late summer bedding plant in public gardens around the Philadelphia, PA area.

Spring Lawn Care Tips

Posted by Hugh on April 9th, 2010

April is time for a minor lawn renovation. All lawn chores should be completed before April 18th, here in the Southern Appalachian region (USDA zones 6a – 7a). If you are planning a major lawn renovation, hold off until September.

Following a rough winter, fertilizing is a positive first step for rapid green recovery and filling in dead spots. Steps for over-seeding small dead areas: 1) light soil tilling with a rake, 2) fertilizing, and 3) seeding.

Over the lawn, apply a crabgrass preventative and again 3 months later (early July). Timing is crucial. When yellow flowering forsythia is passed blooming, crabgrass seedlings have germinated and most preventatives don’t work. Do not apply a crabgrass preventative to recently seeded areas.

Dandelion, henbit, chickweed, wild garlic and other broadleaf weeds are sprayed on non-windy days. Choose a day when air temperatures remain above 60°F for 6 hours or more.

Chart your annual mowing height through the year: first mowing at 1 ½ inches high; after first cut at 2 ½ inches until Memorial Day; during summer at 3 inches; and after Labor Day, back to 2 ½ inches.

Eastern Tent Caterpillar (crabapple, cherry, peach)

Posted by Hugh on April 8th, 2010

photo credit: Dr. Frank Hale, Entomologist, University of Tennessee
The Eastern tent caterpillar is frequently the first insect that I receive calls about in the spring. Eggs overwinter on wild cherry trees and move on long silken treads to tasty landscape tree foliage nearby. Larvae and caterpillars consume lots of leafy matter over the next month.

Dirty white webs form in limb crotches beginning in late March when wild cherry leaves are developing. Larvae leave the web on warm sunny days to consume leaves of ornamental crabapple, peach and cherry. They remain in the web during cloudy or rainy weather.

Large landscape trees are damaged temporarily, and new foliage grows back rapidly. However, newly planted or young trees may lose most of their 1-2 year old foliage and have no reserves to grow new shoots.

In March and April, many different insecticides are labeled including horticultural oil, Sevin (Carbaryl), Bt (Dipel), Orthene, Malathion, and insecticidal soap. Always read the pesticide label for all precautions. For example, the label on Orthene states “may cause foliar injury to flowering crabapples”.

Awesome Ornamental Peach

Posted by Hugh on April 7th, 2010

Photo is an 18- year old ornamental peach tree in Columbia, Tennessee. This tree blooms with 4 different colors bright pink, pink, peppermint, white each year. The tree is full of bloom and obviously well-pruned and cared for.

It may have been a “5 in 1” grafted tree that the home gardener purchased years ago. Ornamental peach is very challenging, susceptible to numerous diseases and insect pests. I congratulate the homeowner for keeping the tree healthy all these years.

Winter Hardy Camellias

Posted by Hugh on April 6th, 2010

pictured: ‘April Remembered’

Growing camellias in the Southern Appalachian region (USDA zone 6-a) is no longer a dream. As many as 40 cultivars of winter hardy camellias to -15 °F are now available. Flower colors range from white, many shades from pink, and red. Hardy cultivars possess big bloom size, long flowering period (fall or spring), and lustrous evergreen foliage.

Start with these outstanding cultivars. For spring blooming, plant ‘Pink Icicle’ (pink semi-double), ‘April Tryst’ (dark red anemone) and ‘April Remembered’ (pink semi-double). Dependable in the fall garden are ‘Winter’s Star’ (pale pink single) and ‘Winter’s Interlude’ (pink anemone).

The culture of camellias is similar to azaleas, rhododendrons and hollies. Plant them on the east or north side of your home or nearby large shade trees, protected from direct summer sunlight and drying winter winds.

Add generous amounts of organic compost, leaf mold or sphagnum peat to maintain an acidic soil pH. Feed shrubs every two months in spring and summer, using either water-soluble Miracle Gro™ or Schultz™ brand fertilizer.

Established shrubs are very drought tolerant after two years, needing water when rainfall is very low. Camellias enjoy relief from most pest problems that plague them further south.

Golden Hakonegrass Lights Up The Shade Garden

Posted by Hugh on March 28th, 2010

Light up dark areas in your shade garden with this wonderful golden ornamental grass from Japan. Golden hakonegrass (Hakonechloa macra ‘Aureola’) grows 12-18 inches tall and 18-24 inches wide with a mounding cascading form.
Very thin green stripes (veins) flow the length of the ½ inch wide golden leaf blade. The cool nights in the fall adds a pink to reddish tinge to the blades before all dies back for a long winter’s nap. Tiny, relatively inconspicuous, floral spikes appear for a short time in late summer.
Golden hakone prospers in moist humus-rich, well-drained soil. Contrarily, it grows poorly in compact heavy clay soils. Hakone prefers a partially shaded garden spot, receiving 2 hours of early morning or 1/2 day of dappled sunlight.
Golden hakone grows slowly, spreading by stolons and rarely trespasses spaces occupied by neighboring hosta, astilbe, heuchera and other companions in the shade garden.
Golden hakone is rarely bothered by disease or insect pests and is not troubled by deer. ‘Aureola’ hakone grass was selected the Perennial Plant of the Year in 2009.

Viburnums for Privacy Screening

Posted by Hugh on March 27th, 2010

photo: the clean summer foliage of ‘Allegheny’ viburnum

Must you plant an evergreen hedge when a semi-evergreen flowering shrub is fine for the task?

Leatherleaf viburnum hybrid cultivars ‘Allegheny’ and ‘Willowwood’ are 60% evergreen, dropping their foliage very late in autumn in U.S.D.A. zones 6 and 7-a. ‘Willowwood is preferred over ‘Allegheny’ in areas of zone 6 and 7 where powdery mildew disease may be a problem.

Prague viburnum (Viburnum pragense) is the only “true” evergreen viburnum. It possesses lustrous dark green foliage year-round and grows to 9-10 feet. Its height is tall enough to become a beautiful privacy screen and noise barrier from the neighbors and traffic.

All three viburnums are excellent growers. They have a distinct advantage over most conifer species used in privacy screening. These lovely viburnums flower in late spring and early summer, something the conifers don’t offer.

When to Prune Flowering Shrubs

Posted by Hugh on March 26th, 2010

Weigela 'Wine and Roses'

Prune spring flowering shrubs and trees immediately within one month after flowering. These plants set their flower buds on last summer’s woody shoots. Common shrub examples include forsythia, lilac, weigela, mockorange, loropetalum, honeysuckle, and many viburnum species.
Summer-flowering plants set their flower buds on spring wood (this year) when they bloom. They are pruned in late summer into early fall (after flowering). You may also wait until late winter into early spring before shrubs leaf out. Some examples are crape myrtles, althea (Rose of Sharon), chaste tree (vitex) and most hydrangeas.
Other tips: remove all dead, diseased, and damaged wood anytime of year. If scale insects are present, remove the worst infested shoots, reducing the need for pesticide spraying.
Prune off weak spindly wood if it takes away from the desired shape or form of the shrub.
Finally, you can reduce shrub height by pruning off the branch(es) at point of origin, near the ground around the base of the shrub.

Lo and Behold ‘Blue Chip’ Buddleia Is Late Summer Gem

Posted by Hugh on March 21st, 2010

photo taken at JC Raulston Arboretum in Raleigh, NC in June 2009

Lo & Behold® ‘Blue Chip’ is a very dwarf butterfly bush (buddleia) for the summer garden. Its compact 3 x 4 foot height and width is an excellent choice planted in a garden bed or in a container on a sunny patio deck or patio. In a large container Blue Chip can stand alone or add a mix of low trailing bedding plants such as petunisa, scaevolas, sweet potato vines, dichondras, or Joseph’s coat (alternanthera).

Lo & Behold® ‘Blue Chip’ maintains its clean growing habit all season long. Gardeners with limited space can attract butterflies and hummingbirds to their garden with this colorful buddleia. It produces loads of fragrant blue flowers which bloom continuously. It thrives in the summer heat and humidity and the foliage remains blemish-free.

‘Blue Chip’ is non-invasive. It’s self-cleaning and will bloom from mid-summer to frost without deadheading. At the start of every spring, prune ‘Blue Chip’ back to 6 inches from the ground, similar to the larger growing buddleias. Within a month new growth will emerge both below and above the soil line. I feed each plant with granular 10-10-10 fertilizer after pruning and add 2-3 inches of mulch. Little additional care is needed through the year.

‘Blue Chip’ blooms from mid-August to late October in my Southern Appalachian garden (zone 6). Buddleias are deer resistant and drought tolerant.

Best of Perennial Veronicas for Gardens

Posted by Hugh on March 17th, 2010

Veronica spicata ‘Royal Candles’ (not evaluated in CBG study)

Chicago Botanic Garden (CBG) has published the results of a 10-year study of speedwells (Veronica and Veronicastrum) in its 33rd issue of Plant Evaluation Notes, “A Comparative Study of Veronica and Veronicastrum“.

Seven speedwells received good-excellent ratings for their overall performance, including Veronica ‘Fairytale’, V. ‘Giles Van Hees’, V. austriaca ‘Ionian Skies’, V. longifolia ‘Blue John’, V. spicata ‘Baby Doll’, V. spicata ‘Ulster Blue Dwarf’, and V. wormskjoldii. These top-rated speedwells exhibited strong growing and excellent flower production throughout the evaluation period. The lack of any serious pest or disease problems, along with good winter survivability, contributed to their high ratings. Additionally, 18 taxa received four-star good ratings for similarly strong performances.

Speedwells are generally easy to grow and prefer sunny locations in moist, well-drained soils. Plants grown in less light will not bloom as profusely and may become lax or open in habit. Crown loss or plant death may occur in wet soil conditions in winter.

Many speedwells require a midsummer shearing after the first bloom to promote a healthy new basal foliage and to encourage late summer flowering. Deadheading of spent blooms produces many new bloom spikes later in the summer. By selecting the best cultivar(s), you should be able to avoid potential foliar diseases, including powdery mildew, downy mildew, leaf spots, and foliar rust.

Generally, plant disease pressure is more severe here in the Southern Appalachian Region than in the Midwest. Read the entire 8 page CBG report (Issue 33, 2010) authored by Richard G. Hawke