‘Green Giant’ arborvitae and Cryptomeria (Japanese cedar) have proven more dependable over the years than Leyland cypress across Tennessee, Virginia, North Carolina, and South Carolina. Leyland cypress is susceptible to three serious foliar diseases.
Some people love the faster growth of Leyland cypress. Leyland cypress may be weak-wooded, as reported by some gardeners this current frigid winter. Fast growing species tend to be weak-wooded. This may be the problem with the heavy snow and high wind storms this past winter.
Ask yourself “do you really need to construct a 50-60 foot green wall so you can hide from the sight and noise of your neighbors”. A 10 to 12 foot screen is usually what most people need.
I would sway you to choosing a shorter and slower growing needle evergreen like Emerald™ arborvitae, any tall-growing evergreen holly (Ilex spp.) or an evergreen flowering shrub like Pragense viburnum.
Privacy Screening – Avoid Using Leyland Cypress
New Dogwoods for Mildew Resistance
‘Bosque’ Lacebark Elm — a Better Choice
(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.
‘Clothed in Glory’ daylily
(Photo courtesy of The Daylily Nursery)
Salt Damage on Trees
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
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
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
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
Winter Flowering Bulbs
Disease-free Apple Varieties–Judge for Yourself
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.