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

Add Some Gold to Your Landscape

Posted by Hugh on January 30th, 2013

'All Gold' Hakone Grass Planted in Container

Is your garden awash in green foliage? A few well placed bright gold-leaf shrubs or perennials can awaken almost any dull green landscape spot. Here are two shrubs, Mellow Yellow® spirea and Gold Nugget barberry, plus one perennial (‘All Gold’ hakone grass) that may add some flair.

Mellow Yellow® Spirea (Spiraea thunbergii ‘Ogon’) forms small white flowers which cover the branches in mid-spring, and bright yellow narrow leaved foliage soon to follow. Branches take on a drooping habit. The yellow leaves fade to green in the summer, and all leaves turn burnt orange in the fall. It grows 4-5 feet in height and spread in full to partial sunlight. Mellow Yellow tolerates dry soils in summer with little leaf burn.

Golden Nugget barberry (Berberis thunbergii ‘Golden Nugget’) offers bright colored foliage which does not burn in the summer heat. Grow in full sun to sharpen its golden hue. Barberry grows well in average soil as long as it is well drained. The foliage develops an orange cast in the cool autumn air. Golden Nugget is a low slow growing plant for the front border.

All Gold hakone grass (Hakonechloa macra ‘All Gold’) shimmers in a partially shaded spot. Foliage holds its spectacular color all summer, especially when sited in morning sunlight. All Gold grows as a neat, cascading mound, 12 inches high and 18 inches wide. It prospers in compost rich soil with regular watering. Just tuck one or more among green leafy plants and see what happens.

Pruning shrubs shortly after spring flowering as spirea and barberry bloom on last year’s wood. Hakone grass is mowed down in late fall to three inches in height. Bees and butterflies visit spirea and barberry flowers in the spring.

Vernal Witchhazel and New Cultivar ‘Quasimodo’

Posted by Hugh on January 24th, 2013

'Quasimodo' Dwarf Vernal Witchhazel (photo by Highland Creek Nursery, Fletcher, NC)

Vernal witchhazel (H. vernalis) is a dense growing 8 to 12 foot native shrub which blooms in mid-winter in the Southern Appalachian region (USDA hardiness zones 6 and 7). It is winter hardy to zone 4. Small ½ inch wide yellow flowers, flushed red at the base, emit a pleasant witchhazel aroma in the February garden. Often, it’s the fragrance that attracts gardeners to the small strap-like flowers blooming in the winter garden.

New leaves flaunt a reddish purple tint in early spring. The 2 – 5 inch long by 2 – 3 inch wide leaves are medium green and remain pest free throughout the growing season. Fall leaf colors gradually change from green to yellow to gold. Unfortunately, many dead leaves often hang on through the winter, concealing many of the winter flowers. Vernal witchhazel’s root system tends to sucker prolifically. The branch wood displays a pale gray color.

‘Quasimodo’ is a compact 3 – 4 foot high shrub, slightly taller than wide. This diminutive cultivar is an excellent choice for a small garden. Quasimodo was hybridized and introduced by Pieter Zwijnenburg in the Netherlands. Quasimodo drops most leaves in late fall so that its burnt orange flowers are in plain sight in the mid-winter landscape. Winter flowering period may last 3-4 weeks.

Vernal witchhazel grows in full sun to moderate shade and requires little extra care. The soil should be adequately drained and mildly acidic.

Fragrant Honeysuckle Is Long-Lived Heirloom Shrub

Posted by Hugh on January 21st, 2013

Fragrant Honeysuckle on Mid-January Day at Biltmore Estates, Asheville, NC

Old Pruned Shrub at Biltmore Estates, Asheville, NC

Fragrant honeysuckle (Lonicera fragrantissima) has creamy white flowers which open in January during a brief warm-ups and continues, off and on, through February and March in the Southern Appalachian region (USDA hardiness zones 6 and 7). It is an old heirloom shrub indigenous of China. It’s hardy in USDA hardiness zones 4-8.

Fragrant honeysuckle is beloved for its lemony floral scent in the winter. Gardeners cooped up in their homes may force cut boughs indoors. It typically grows 8-10 feet tall and wide, although taller unkempt shrubs are easy to find in old landscapes in the South.

Rounded shaped leaves are 1-3 inches long and tend to hang into late fall with little significant color change. The 1/4 inch green berries ripen dark red in late May and the dark bluish-green spring foliage hide most of them. The bark sheds off in narrow strips.

Fragrant honeysuckle asks for little care and grows in adequately drained average soil. This shrub should be pruned annually from late winter or spring after most flowering is completed. Disease and pest problems are rarely an issue.

Fragrant honeysuckle can be utilized as a low cost deciduous privacy screen. Old plants may be cutback to a few inches above ground with a chainsaw, (called “renewal pruning”), and fed 2-3 handfuls of 10-10-10 granular fertilizer broadcast at least 6-12 inches away from the shrub base.

Information from Mr. John Elsley, South Carolina plantsman: ‘Winter Beauty’ (L. purpusii ‘Winter Beauty’) is a showier winter flowering selection of fragrant honeysuckle. It is a hybrid cross between L. fragrantissima x L. standishii, and has been listed in Hillier Nursery catalog in England. Its winter blooming creamy white flowers are slightly larger and highly fragrant.

Regarding possible invasive issues, fragrant honeysuckle blooms very early when most insect pollinators are not active. Seedlings are rarely found growing around shrubs.

‘Otto Lukyen’ Cherry Laurel Exhibits Better Winter Hardiness

Posted by Hugh on January 17th, 2013

'Otto Luyken' cherry laurel (photo credit- Michael Valk, Evergreen Garden Center, Johnson City, TN)

Otto Luyken (Prunus laurocerasus ‘Otto Luyken’) is a very compact form of cherry laurel. It produces showy, fragrant, erect white spike flowers primarily in the spring, and repeats with light blooming thru the summer months.

Its fragrant white flowers are showy racemes which rise several inches above the foliage in mid-spring. Its glossy pointed tip leaves are steadfast green all four seasons long and exhibit better pest resistance than other cherry laurels in that size class. Presence of shot-hole disease, powdery mildew, and root rot, is mostly the result of poor planting site or exceptionally dry summer weather.

Otto Luyken forms a low foundation specimen or group several into a low hedge. It has a moderate growth rate, 3 to 4 feet high and 5 to 6 feet spread in first 5 years. Utilized it as an evergreen substitute for hollies and boxwoods. Its foliage tends to remain full right to the ground.

Otto Luyken is a relatively low maintenance shrub. It is best pruned immediately after flowering. The black drupes fruits ripen in mid-summer and attract many kinds of birds to your landscape.

Otto Luyken grows best in full sun to partial shade and in a moist well-drained moist soil. Cherry laurel does not tolerate standing water around its base. It copes with an alkaline soil pH, although best in an acidic soil. Its foliage is both salt tolerant and inner city urban pollution.

Skip (Schipka) Laurel Creates Dense Evergreen Privacy Screen

Posted by Hugh on January 14th, 2013

Schip Laurel Screen or Hedge in Johnson City, TN

Schipka laurel (Prunus laurocerasus ‘Schipkaensis’) is a dense growing evergreen shrub with lustrous evergreen foliage and clusters of small white flowers in the spring. It is rated as one of the cold hardiest of cherry laurels (USDA hardiness zone 6-8). In the garden center it is often labeled ‘skip laurel”.

Skip laurel grows 10 to 12 feet tall, and is often utilized as a medium 6 to 10 foot tall privacy screen or hedge through judicious pruning one to two times annually. It grows best in full sun to partial shade and in a moist well-drained soil. Good soil drainage and proper air movement are crucial to avoid outbreaks of potentially serious disease and pest problems.

The handsome evergreen leaves are 2 to 6 inches long and one-half that in width. Foliage is both salt tolerant and holds up to urban pollutants. Skip laurel is tolerant of alkaline soils, but leaf color is darker green in an acidic soil.

Large, upright clusters of small creamy white blossoms lay on 2 to 5 inch long racemes which originate off the leaf axils in late April into May. Many flowers are hidden amid the thick mass of foliage. Flowers often emit an over-powering odor. Small purplish black drupe fruits ripen in late summer and are quickly consumed by birds.

Cherry laurels are indigenous to southeastern Europe and southwestern Asia; schip laurel originates near the Shipka Pass in Bulgaria.

Will The Best Cherry Laurel Please Come Forward?

Posted by Hugh on January 10th, 2013

Cherry Laurel at Bartlett Tree Lab, Charlotte, NC

Not all cherry laurels (Prunus laurocerasus) are created equal. “Skip” laurel (var. Schipkaensis) and Zabel (var. ‘Zabeliana’) are large size shrubs at 9 to 10 feet in height and 6 to 8 feet in width. Both cultivars are rated the cold hardiest of the tall growing types . ‘Otto Luyken’ is the hardiness small leaf form at 4 to 5 feet in height and 6 to 8 feet in width (USDA hardiness zone 6).

Disease and pest maladies abound, primarily when they’re planted in a poor landscape environment and the site problems are allowed to mount up before proper action is taken. Good soil drainage is a must for cherry laurels. Many varieties become riddled with scale insects, stem cankers, and bacterial shothole disease. Extreme summer drought brings on canker and shot hole diseases. Shoddy irrigation practices often worsen the problems.

Diseased black cherry trees (P. serotina), growing wild in fence rows, contribute to the spread of fungal shot hole on cherry laurel cultivars. Defoliation may not always occur even though spotting is visible.

Pruning off diseased branches and spraying pesticide help to reduce or eliminate disease infections. Banner MAXX® or Captan® fungicides at spring bud break protect healthy foliage from fungal shot hole.
Bacterial shot hole is also common in skip and Otto Luyken cherry laurels. Avoid using any one pesticide more than twice in a year to reduce the risk of building resistance.

Witchhazels Invent Their Own Season

Posted by Hugh on January 7th, 2013

Hamamelis x intermedia 'Gingerbread' blooming in February

Witchhazels (Hamamelis spp.) are medium to large shrubs which can be shaped into small trees by judicious pruning. In general, all witchhazels grow in full sun but can prosper with moderate amounts of shade. Other than pruning, they require little extra care. Plant in any soil type as long as it is adequately drained and mildly acidic.

Species native to the Eastern United States include American witchhazel (H. virginiana) and vernal witchhazel (H. vernalis). Asian species include Chinese witchhazel (H. mollis), Japanese witchhazel (H. japonica), and hybrid forms (H. x intermedia). The witchhazel flower color palette ranges from pale yellow, deep gold, copper, and purplish red.

In calendar order, first to flower is Vernal witchhazel (USDA hardiness zone 4). Vernal is a densely branched 8 to 12 foot shrub which blooms from early to mid-winter. Usually, flowering follows a short warm period. Small ½ inch wide yellow flowers, flushed red at the base, emit a pleasant witchhazel aroma.

The Asian witchhazels follow from mid-February thru most of March. Flowers of many new cultivars are larger and brighter colored. Among witchhazels the Asian forms present the widest flower color palette and have increased in popularity as a group

American witchhazel is the last to bloom in October and November in Southern Appalachian region (USDA hardiness zones 6 and 7). This witchhazel grows tall and is frequently pruned into an 18-25 foot tree.

All witchhazels turn pale yellow to dark golden foliage colors in autumn.

Pest Update – More Pesticide Options for Hemlock Adelgid Control

Posted by Hugh on January 3rd, 2013

Canadian hemlock short needle foliage

Twenty years ago predictions of the demise of our native Canadian (Tsuga canadensis) and Carolina hemlocks (T. carolina) from home and commercial landscapes turned out to be incorrect. The key reason was the effectiveness of the insecticide Imidacloprid®. This product is licensed by Bayer AG, and is found in a number of lawn and garden products, including Bayer Advance Garden Tree and Shrub Insect Control™ and Merit 75 WP.

Imidacloprid is a systemic insecticide. When properly applied to the soil near the hemlock trunks, it must be carried down into the soil and absorbed through the hemlock roots. The pesticide is applied to the soil Read and understand the easy package directions and watered in chemical within 24-36 hours. Do not expect rainfall to carry it down to roots.

There is even better news. Yearly applications is generally unnecessary. Imidacloprid appears to be more effective than the manufacturer’s recommendations. Hemlock adelgids do not destroy a hemlock tree or shrub hedge in 1-2 years. It may take 2-3 years before serious visual damage is observed.

Other insecticides labeled for use in the landscape may be sprayed to kill the crawler that hatches from the insect egg. Labeled products include Merit (imidacloprid), Talstar (bifenthrin), Onyx (bifenthrin), Astro (permethrin) and Safari (dinotefuran). Talstar is most widely used, providing excellent control any time through the growing season. Control from spraying Talstar has given two and sometimes three years of control. Do not spray trees if the material will drift into open water or other property.

Lastly, Safari 20 SG has slightly faster uptake by the tree as a soil drench or bark spray than products containing imidacloprid. Currently, it is sold only to state certified licensed landscape professionals.

All products are available at garden centers and farm supply stores.

Long-Lived Cedar of Lebanon – A Record Of Human History

Posted by Hugh on January 1st, 2013

Lovely Tufted Needles of Cedar of Lebanon at Arnold Arboretum In Boston, MA

Cedar of Lebanon (Cedrus libani) is a tree aristocrat among conifers. Among the true evergreen cedars it is rated the cold hardiest (USDA zone 5). Its broad horizontal branching and dark green needles defines this tree. The bright green tufted needles are less than 1 inch long and not as showy as the more popular Atlas cedar (C. atlantica) from Morocco.

In its first 25-40 years, cedar of Lebanon takes on a predominantly vertical form. As the tree ages, branching widens and develops its distinctive, flat-topped canopy. Its tufts of 30 to 40 short evergreen needles are borne on short spurs. The 4-inch barrel-shaped cones lie upright on the branches. The cones take two years to mature and disperse seed in late autumn.

Cedar of Lebanon grows slowly, less than one foot per year. The long-lived cedar becomes grander with age. At full maturity, it may reach 60-70 feet in height and spread. Starting out, give it lots of room and a full day of sunlight. The soil should be moist, loamy and well-drained. A large specimen tree demonstrates good heat and drought tolerance, but is susceptible to urban air pollutants.

Cedar of Lebanon is the tree that seems a part of recorded human history from the Phoenician, Egyptian and Roman Empires. Traveling through England, you can’t miss seeing hundreds of lovely tall specimens planted almost 200 years ago, commemorating Napoleon’s defeat at Waterloo in 1815. Efforts are in progress to reforest trees in the geographic area between Lebanon and Turkey where it is indigenous.

Cedar of Lebanon is best planted on park grounds, golf courses, and other large properties. A few dwarf forms are available for purchase from on-line specialty conifer nurseries.

Add A Little Muscle To Your Landscape

Posted by Hugh on December 28th, 2012

American hornbeam at NC Arboretum in Asheville, NC

Underutilized and underappreciated. That’s American hornbeam (Carpinus caroliniana), aka ironwood or muscle wood. It grows primarily in moist, slightly acid soils along woodland rivers and streams. Our native hornbeam possesses the ability to adapt to a range of landscape situations. It grows equally well in full sun or partial shade.

Its dark green summer foliage is rarely troubled by disease or pest problems. Its autumn foliage turns intense shades of yellow, orange and scarlet, depending on soil pH and the provenance of the species. It tolerates either wet or dry soils, but should provide adequate drainage. Hornbeam copes with urban conditions better than most. It survives in tough environs such as non-irrigated planting islands in parking lots. Contrarily, it’s an ideal choice for planting in rain gardens.

Ironwood blooms in spring, with separate male and female catkins. While the male catkins are not particularly showy, the female catkins form unique clusters of winged nutlets that are clearly visible in the fall. The nutlets provide mast for numerous forest fauna. Its grayish fluted bark gives the trunk and branches a muscular feature which is easily identifiable in the winter woods.

Hornbeam grows 20 to 35 feet tall and nearly as wide. The tree often grow multi-stemmed. With clean summer foliage, interesting fruits, good fall color and attractive winter bark, hornbeam makes an excellent specimen or patio tree. It also works as a deciduous green privacy screen.