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

‘Bosque’ Lacebark Elm — a Better Choice

Posted by Hugh on February 10th, 2010

(New planting of Allee elm pictured)

Recent storm damage has caused a re-evaluation, whether to continue to plant the cultivar Allee®, also called ‘Emerald Vase’. Urban foresters around the state of Tennessee report that limb breakage and clean up around Allee elms is greater than around other cultivars. Bosque seemed to fare much better.
Lacebark elm (Ulmus parvifolia) is a beautiful medium -sized street and shade tree. Its use in urban street plantings has become popular over the past decade. The three leading cultivars of lacebark elm are Allee®, Athena® and Bosque™.
The tree earns its name from the delightful orange or brown color mosaic or puzzle-like pattern over the main trunk (s) and branches. The autumn leaf color is rarely memorable and the small 1-2 inch leaves fall without much fanfare and with little mess.

Get your lacebark off to a long and prosperous life by supplying extra water and light fertilize feeding the first two years. In the first two years after planting, a young tree needs deep watering every two weeks in the late spring and summer. An established lacebark elm exhibits exceptional drought tolerance.

If you or your city, town or village is planting lacebark elm in your housing subdivision, request that they select Bosque elm.

‘Clothed in Glory’ daylily

Posted by Hugh on February 10th, 2010

(Photo courtesy of The Daylily Nursery)

Browsing through several garden catalogs on this snowy February day, I spotted a new daylily gem called ‘Clothed in Glory’ from The Daylily Nursery, a mail order emporium in Rock Island, TN.

Tim Hitchcock, nursery owner, describes ‘Clothed in Glory’ as an 18- inch tall lavender beauty possessing regal golden frilled-edged petals with a yellow center eye. Each flower measures 7 inches across and the floral bud count is enormous. ‘Clothed in Glory’ re-blooms in early fall if kept watered and fertilized over a hot, dry summer.

Daylilies are low maintenance perennials which grow in any well-drained soil. Very few disease and insect pests bother them. Plant them in early spring and daylilies will bloom their first summer (late spring). Divide daylilies every 5-6 years to maximize flower numbers.

With over 84,000 registered daylily daylilies in the world marketplace, gardeners still rally around the popular 18-22 inch tall landscape cultivars: ‘Stella D’Oro’, ‘Pardon Me’, and ‘Happy Returns’. I recommend adding ‘Clothed in Glory to your garden this spring.

Salt Damage on Trees

Posted by Hugh on February 1st, 2010

Winter 2010 lingers on across Tennessee, Virginia and North Carolina. The white coating of de-icing salts over streets and highways can damage many trees and shrubs. Salt spray and salt deposits may also leach into the soil and become equally damaging. Plant species vary in their sensitivity to salt injury.
Browning of the tips of needle and broadleaf evergreens is a typical symptom of salt injury. Needle loss can be an extreme result, with evergreen branches becoming progressively bare. Often, evergreens become so weakened and stressed that new spring growth does not slow the needle/leaf loss. Overall tree health gradually declines.

The following practices can minimize salt injury to trees and shrubs:
1. Applications of water will leach some salt out of the root zone. Plentiful spring rainfall will help in this leaching/cleansing process. As much as 6 inches of water is needed to leach about half the soluble salts. In addition, applying gypsum (calcium sulfate) displaces the sodium in the soil.
2. Plant trees in salt-prone areas that are less vulnerable to salt damage. All trees are affected by salt to some degree, but some species are more tolerant than others. A listing of the susceptible and resistant trees to salt (University of Tennessee Extension publication SP-610) appears below.
3. In future plantings, avoid setting salt susceptible tree species in areas where salt-laden brine and slush are likely to accumulate.
4. Plants that are injured and exhibit dieback should be watered, pruned and fertilized.
Fresh mulch may be applied to help reduce water loss during the normally dry summer ahead. Weakened or stressed trees are also more susceptible to disease and insect pests.

Table 1. Salt Susceptibility of Trees
Vulnerable to Salt
Red Maple – Acer rubrum
Sugar Maple – Acer saccharum
Mimosa – Albizia julibrissin
Serviceberry – Amelanchier spp.
American Hornbeam – Carpinus caroliniana
Dogwood – Cornus florida
Hawthorn – Crataegus spp.
American Beech – Fagus grandifolia
Yellow Poplar – Liriodendron tulipifera
Crapemyrtle – Lagerstroemia spp.
Magnolia – Magnolia grandiflora
Spruces (most) – Picea spp.
Eastern White Pine – Pinus strobus
Scotch pine – Pinus sylvestris
Lindens – Tilia spp.
Eastern Hemlock – Tsuga canadensis

More Tolerant to Salt
Norway Maple – Acer platanoides
Buckeyes – Aesculus spp.
Birch – Betula spp.
Hickories – Carya spp.
Ash – Fraxinus spp.
Ginkgo- Ginkgo biloba
Honeylocust – Gleditsia triacanthos
Black Walnut – Juglans nigra
Eastern Redcedar – Juniperus virginiana
Cottonwood/Aspens – Populus spp.
Cherries – Prunus spp.
Oaks (most) – Quercus spp.
Black Locust – Robinia pseudoacacia
Yews – Taxus spp.
Elms – Ulmus spp.

Ferns in Your Garden

Posted by Hugh on January 22nd, 2010

I recommend adding ferns in your shade garden. Ferns offer very fine textured foliage. Plant’em in clumps of three or more. Select the proper fern by your garden site, e.g whether it is likely dry or moist soils. Some grow surprisingly well in full sun, but most prefer partial to full shade. Don’t buy a collection of different ferns for planting in one garden place. Instead, select them by their light and soil moisture needs.

Here are four species which are easy to grow:

Christmas fern (Polystichum acrostichoides)
Autumn fern (Dryopteris erythrosora)
Lady fern (Athryium felix-femina)
Northern maidenhair fern (Adiantum pedatum) – (pictured)- prefers well-drained, highly composted soils and supplemental moisture during long summer dry spells. Keep soil near pH 7.0 (neutral) by occasional liming every few years if soil pH drops.

All four are not finicky, demonstrate good drought tolerance and grow in soil with little to no additional soil prep. Ideally, you should grow them in a richly composted garden soil along with adequate moisture over long dry spells. Bi-monthly feeding with a water soluble fertilizer such as Miracle-Gro™, Jack’s™, or Nature’s Source™ from April to August will get all off to a good start in the first year.

Better Winter Blooming Witchhazels on the Way

Posted by Hugh on January 16th, 2010

Chinese witchhazel (Hamamelis mollis) are a mid-winter garden delight. Depending on the cultivar, small yellow, orange or red flowers open in early February. Flowers survive many cold nights unharmed over several weeks.

Most of the Hamamelis x intermedia hybrid types hold onto their leaves during the winter in the southeast. The popular cultivar ‘Arnold Promise’ is one of the worst offenders for winter leaf retention.

Chinese witchazels retain (don’t drop) their dried leaves through most of the winter, essentially hiding most of the tiny flowers beneath them. Autumn weather plays an important factor. If fall temperature drops are gradual, leaves will drop. A warm fall followed by a quick cold snap will stick leaves to branches all winter long. Often, this is what occurs in the southeastern U.S. (garden hardiness zones 6b – 8a).

1-15-10 Conversation with Brian Upchurch at Highland Creek Nursery in Fletcher, NC
Brian recommends planting Chinese witchhazel cultivars which tend to shed all foliage before flowering starts. His favorites are ‘Wisley Supreme’ (bright yellow blooms), ‘Robert’ (orange) and ‘Twilight’ (red). He adds that all three do not suffer from powdery mildew foliar disease as Arnold Promise does over the summer months. He adds that the cultivar ‘Westerstead’ is a better choice than Arnold Promise in the hybrid witchhazels.

Trees for the Urban Environment

Posted by Hugh on January 8th, 2010

Sulfur dioxide, nitrogen oxides, carbon monoxide, chlorine, fluorine, and ozone are the leading air pollutants that injure tree and shrub foliage in the Tennessee urban landscape. A single tree, depending on species and the genetic (cultivar), may respond differently to particulate and gaseous pollutants. The stage of growth and how close it is growing near the source of the pollution may determine the degree of foliar injury in the tree.

In addition, urban trees are exposed to other environmental stresses such as soil compaction, toxic salts, disease and insect pests. Environmental stresses may develop foliar injury symptoms which appear very similar to those of air pollution.

The following tree species are best adapted to the urban environment:

Small Trees – Suitable Near Overhead Utility Wires (lines under 20 feet)

Amur Maple Acer ginnala

Three-flower Maple Acer triflorum

Shantung or Painted Maple Acer truncatum

Red Horsechestnut Aesculus X carnea

American Hornbeam Carpinus caroliniana

Chinese Fringe Tree Chionanthus retusus

Cornelian cherry Dogwood Cornus mas

Japanese Cornel Dogwood Cornus officinalis

American Smoketree Cotinus obovatus

Winter King Hawthorn Crataegus viridis ‘Winter King’

Goldenrain Tree Koelreuteria paniculata

Amur Maackia Maackia amurensis

Galaxy Magnolia Magnolia X ‘Galaxy’

Flowering Crabapples Malus X ‘Prairifire’, ‘Sugar Tyme’, zumi ‘Calocarpa’, ‘Adams’, ‘David’, ‘Donald Wyman’, ‘Adirondack’, ‘Louisa’, others

Persian Parrotia Parrotia persica

Okame Cherry Prunus X incamp ‘Okame’

Japanese Tree Lilac Syringa reticulata

Medium to Large Trees – NOT Suitable Near Overhead Utility Lines

Trident Maple Acer buergerianum

Hedge Maple Acer campestre ‘Queen Elizabeth’

Red Maple Acer rubrum ‘Red Sunset’, ‘October Glory’

Sugar Maple Acer saccharum ‘Legacy’, ‘Green Mountain’

Heritage ™ River birch Betula nigra ‘Cully’

European Hornbeam Carpinus betulus ‘Fastigiata’

Sugar Hackberry Celtis laevigata

Common Hackberry Celtis occidentalis

Katsura Tree Cercidiphyllum japonicum

American Yellowwood Cladastris kentuckea

Turkish Filbert Corylus colurna

White Ash Fraxinus americana – Emerald ash borer may be serious potential pest

Green Ash Fraxinus pennsylvanica – Emerald ash borer may be serious potential pest

Ginkgo Ginkgo biloba – plant only male cultivars to avoid malodorous fruit.

Thornless Honey Locust Gleditsia triacanthos ‘inermis’

Kentucky Coffeetree Gymnocladus dioica ‘Espresso’

American Sweetgum Liquidambar styraciflua ‘Rotundiloba’ (almost seedless)

Tulip Tree Liriodendron tulipifera

Dawn Redwood Metasequoia glyptostroboides

Black Gum, tupelo Nyssa sylvatica ‘Wildfire’

American Hophornbeam Ostrya virginiana

Chinese Pistache Pistacea chinensis

London Planetree Platanus X acerifolia ‘Bloodgood’, ‘Yarwood’, ‘Liberty’

Sawtooth Oak Quercus acutissima

Swamp White Oak Quercus bicolor

Shingle Oak Quercus imbricaria

Pin Oak Quercus palustris

Willow Oak Quercus phellos

Northern Red Oak Quercus rubra

Bald Cypress Taxodium distichum

Littleleaf Linden Tilia cordata

Silver Linden Tilia tomentosa ‘Sterling’

American Elm Ulmus americana ‘Princeton’, ‘Jefferson’

Lacebark Elm Ulmus parvifolia ‘Bosque’, ‘Athena’

Japanese Zelkova Zelkova serrata

Disease-free Apple Varieties–Judge for Yourself

Posted by Hugh on January 6th, 2010

Weekly spraying of home apple orchards for the dreaded apple scab is a total downer. Over the past half century have come the first scab-free immune apple varieties: Prima, Priscilla, and Sir Prize. However, Prima and Priscilla will never win any taste awards.

All 3 varieties are very susceptible to other apple disease maladies as cedar-apple rust, powdery mildew and fire blight. All are rated as dessert quality, possessing a short shelf life after picking.

Currently, the Penn State Extension website lists Freedom, Enterprise, Liberty, Novomac, Pristine, Redfree and Sundance with good resistance to 3 of the 4 major diseases.

Select 2 -3 varieties as apple trees require cross-pollination. Purchase them on a dwarf or semi-dwarf rootstock, properly prune them annually, and you’ll be harvesting fruit from trees in 3 years.

Pruning An Old Nandina

Posted by Hugh on January 5th, 2010

Nandina (Nandina domestica) is often mis-pruned. By shearing or topping nandina foliage, blooms and resulting berries are lost (see photo). The plant eventually becomes leggy and thin.

Sharply prune back about a third of the taller stems at the base of the shrub in March before spring growth begins. Stagger the cuts 3 to 6 inches above the soil. Within a few months new shoots begin to grow out near the soil line, eventually filling in around the shrub base. The regrowth gives the nandina a fresh appearance.

Why My Tree Or Shrub Doesn’t Bloom

Posted by Hugh on January 5th, 2010

Frustrated by a fruit tree or ornamental tree that does not bloom? There are 5 primary causes:

Lack of sunlight – insufficient light reduces flower bud development
Fertility – too much nitrogen fed to plants can over-stimulate vegetative growth, either delaying or preventing flower bud development
Winter injury or chilling tender flower buds in one or more spring frost
Pruning at the wrong time of year, essentially removing all flowering wood
Alternative (biennial) flowering when a plant bears too much fruit and will not initiate new flower bud for the next year

All these factors are inter-related. While bad pruning practices may reduce flower bud numbers, good timely pruning practices increase blooming. Usually, an unpruned tree or shrub does not bloom heavily. A shrub or tree with an open branch canopy in full sun will flower reliably every year.

Prune spring flowering shrubs and trees immediately after flowering. These plants set flower buds on woody growth produced in the summer. Summer-flowering plants set their flower buds on spring wood in the same year when they bloom. They can be pruned in late summer or wait until late winter and early spring.

Big Begonias

Posted by Hugh on January 4th, 2010

The Benary ‘Big Begonia’ series are a hit, “begonias on steroids”, some gardeners may say. Individual flowers are twice that of other bedding begonias. Colors are vivid with three cultivars currently available . ‘Big Rose Bronze Leaf’ is my personal favorite. (pictured)

Begonias grow best in well drained, humus-rich garden soil. Provide tender -loving care for the first 4 weeks in the spring, and plants will bloom non-stop through a long hot, dry summers into the first hard frost autumn.

Plant the Big begonias in full sun or partial sun (a minimum of 5 hours of sun recommended). Disease and insect pests are rarely an issue for these tough, non-stop flowering annuals. Do not plant begonias in the same garden spot more than 3 consecutive years to avoid buildup of soil pathogens.