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

Urban Trees Reap Cleaner Air

Posted by Hugh on January 30th, 2014

Urban Tree Planting In Downtown Charlotte, NC

U.S. Forest Service scientists with the Center for Urban Forest Research report that planting and nurturing street trees in Indianapolis, IN returned 500 percent in benefits from storm water reduction, energy conservation, cleaner air and increased property values.

The researchers evaluated more than 117,000 trees the city’s Parks and Recreation Forestry Section manages. It found that every $1 spent brought a $6.09 return. Each tree annually removed 1.5 pounds of air pollutants, valued at $2 per tree or $212,000.

“Indianapolis’ urban forest is uniquely diverse, with only one of over 170 species representing slightly more than 10 percent of the total tree population,” said Greg McPherson, Center for Urban Forest Research director. Species diversity is important because the urban forest is at less risk of catastrophic losses from diseases or pests.”

Scientists found Indianapolis trees annually intercept 318.9 million gallons of rainfall, an estimated worth $1.98 million or $17 per tree per year. Trees also annually cut electricity use by more than 6,447 megawatt hours, worth $432,000. They reduce natural gas use by more than 150,000 therms, yielding annual benefits of $165,000 or $5 per tree.

Total annual tree benefits varied by species and size. For example, silver maples (Acer saccharinum), representing the largest species planted, produced the greatest benefit at $60 per tree, but they also were the most expensive to manage. Several were nearing the end of their productive lives and required removal or intensive care.

Source: U.S. Forest Service, Center for Urban Forest Research, January 2014.

Winter Sap Bleeding From Trees Not Harmful

Posted by Hugh on January 28th, 2014

Icicle Off Poor Pruning Cut in Fall

Winter can be a cruel period for trees. Day-night temperatures may wildly fluctuate and drying winds tend to injure tender buds. Maples (Acer spp.), flowering dogwoods (Cornus florida), birches (Betula spp.), yellowwoods (Cladrastis kentukea), walnuts (Juglans spp.) and elms (Ulmus spp.) are “bleeders”. The sap pressure inside branches is highest during the winter months.

If any tree jeopardizes a house, property, utility lines, and human safety, it should be pruned no matter the time of year. The bleeding sap phenomena is over-rated. Winter-pruned bleeder trees will not die. If it humanly bothers you, prune these “bleeder” species in the summer when sap pressure is lowest.

Leaky sap may drip on pedestrians, cars, and walkways resulting in stains on trunk bark and sidewalks. Puddles on walkways may freeze and create slippery pavement.

Bleeding or sap loss will eventually stop on its own. Quickly, the pruning wound cuts have internally sealed off and the healing process started.

Spraying paint (wound dressing) does not help. Many times the sap flow is so plentiful as to wash the wound paint off. You may want to irrigate the tree during dry spells to speed wound healing.

If you’re seeking advice about pruning large shade trees, consult a certified arborist first. The International Society of Arboriculture (ISA) website should list one or more in your area.

Soil Sampling Is Good Insurance

Posted by Hugh on January 25th, 2014

Soil sampling is good gardening insurance!

Do you know what your soil needs to grow a great lawn, flower, or vegetable garden? If you haven’t analyzed the soil in the past five years, get it done in any season. Most gardeners do it in late winter when university, state, and private soil labs are busiest.

The local Extension office or a garden center can supply you with one or more sample kits with instructions and forms detailing how to sample. Mail the soil, form, and money to the soil lab.

If soil conditions have drastically changed because great amounts of organic matter, topsoil, etc. were added or accidentally spilled fertilizer or another chemical, retest your soil. Do you have a special problem area? Separately test this spot and explain the problem. Photos are optional.

In early fall, before you’re ready to tackle a major fescue/bluegrass lawn renovation, soil test before the work starts. Be sure to mark on the form that you want recommendations for a lawn. With a lab results in hand, they detail how many pounds of fertilizer to apply. If lime or sulfur to raise or lower the soil pH, that is included on your report.

If you’re planting acid-loving plants such as azaleas, blueberries or mountain laurels (Kalmia app.), inform the soil lab; they will estimate when and how much sulfur to apply. Planning a home fruit orchard (apples, peaches, plums, grapes, brambles), tell the lab intended use of the land.

Basic sampling instructions: using a trowel, take 8-10 random samples of topsoil from various parts of your yard. Dig only 5-6 inches deep. Mix all together thoroughly in a bucket. Place a small amount of the soil mixture in a paper (not plastic) bag or box, enough to fill a small baby food jar. Do not ship wet soil.

“Death By Mower” Disease

Posted by Hugh on January 22nd, 2014

Dead Dogwood By “Mower Disease”

“Mower disease” is a totally preventable human malady caused by permitting lawn grasses and weeds from growing near the crown of trees and shrubs. The problem is commonly seen on large properties such as church grounds, cemeteries and public parks. Large gang mowing machines (with many reels) cut 95-98% of the turf area. Workers follow along with push mowers and string, blade weed-eaters or “weed wackers” around trees and shrubs.

String mowers are blamed for most of the unsightly bark injuries. The tree or shrub is eventually weakened by sap leakage and nutrient loss. The damage also exposes the tree/shrub crown to numerous disease infection and insect borers.

A better management practice is to maintain a thin organic mulch zone around the tree or shrub base. The mulch should never be piled up against the trunk. A mulch layer more than 4 inches is not recommended.

Weeds will eventually grow on surface of decaying mulch barrier. Periodically, hoe or hand-pull invading grasses and weeds atop the mulch. An alternative is to spray a weed herbicide such as Round-up™ or an equivalent product according to label directions. When done, add 1-inch of mulch for a fresh clean appearance.

Nativars – New Cultivars Of Native Plants

Posted by Hugh on January 20th, 2014

Improved Serviceberry Nativar ‘Autumn Brilliance’

Nativar is a new term coined by Dr. Allan Armitage, Professor Emeritus from the University of Georgia. It combines the words “native” and “cultivar”. Nativar refers to a cultivar of a native plant. It attempts to excite the horticultural marketplace about new cultivars of native perennial plants, such as blackeyed Susan (Rudbeckia spp.), purple coneflower (Echinacea purpurea), coreopsis (Coreopsis spp.), and many others.

Nativars are native plants that resulted from natural or man-made cross pollination. Many natives have undergone a so-called “facelift”, one that enhances the plant’s appeal or improves past deficiencies such as better flowers or disease resistance. The “new and improved” versions drive new sales of natives to professional landscapers and gardeners. This excites their pop and sizzle at the garden center.

A native tree may not develop good fall color. When an individual plant is spotted in a nursery row or in a forest, the nativar is born, tested, named, and propagated. Plant scientists at the University of Tennessee found anthracnose resistant flowering dogwood (Cornus florida) in a Maryland forest. It was tested, propagated, and named ‘Appalachian Spring’. Since its introduction sales of native dogwoods have increased.

A single nativar may be derived from a large seedling population which possesses wide genetic variability for its ecological surroundings. The nativar may not excel over thousands of acres. For example, a nativar exhibiting deep red fall color may not express this color trait a thousand miles away.

Provenance, where the plant originates, plays an important role. Red maples (Acer rubrum) grow in a wide geographical area in the U.S. and Canada. A cold hardy red maple from Wisconsin will likely not survive a hot humid Georgia summer; a Georgian red maple may not cope with a hard Wisconsin winter. An Oregon red maple nativar with flashy red fall color may fizzle in the southeastern U.S.

Native aster species (Symphyotrichum spp.) grow over a wide geographic area of the eastern U.S. Not all aster nativars planted on a single site will flourish.

Baptisia ‘Purple Smoke’ is hybrid nativar of two species

European Hornbeams Serve As Great Garden Sentinels

Posted by Hugh on January 17th, 2014

Touch of Fall Color on Carpinus betulus 'Columnaris'

Upright European hornbeams (Carpinus betulus cvs.) are versatile small to medium-sized deciduous trees that fit most landscape settings. Depending on which cultivar you select, the tree stands with a narrow vertical profile. It grows 35-40 feet tall and 15-20 feet wide. It’s cookie cutter by design as a street tree or tall narrow hedge.

Hornbeams are best planted in late winter balled and burlapped (B&B) and in any month if container-grown. Tall popular cultivars ‘Fastigiata’ and ‘Columnaris’ are being supplanted by shorter growing ‘Frans Fontaine’.

Leaves are small, dark glossy green on the surface and finely serrated along the edge. Autumn foliage turns golden yellow. Tiny spring flowers and pendulous clusters of samara seeds are ornamentally insignificant. European hornbeam is often nicknamed “muscle wood” or “ironwood” as its smooth gray main trunk is muscular.

Annual growth rate is slow. Hornbeams are long-lived when properly sited and nurtured. They prefer in moist, well-drained, acidic to slightly alkaline pH soil. Full open sunlight or partial 5 to 6 hours of sunlight is adequate. Newly planted trees should be irrigated every 7 to 10 days over the first two summers if summers are unusually dry. Otherwise, hornbeams are moderately drought tolerance. Fertilize young trees in late winter with granular 10-10-10 or equivalent. Pruning is rarely needed except to maintain the narrow upright form.

Young trees may be fashioned into a tall hedge or screen, set out 5 to 10 feet apart. Create a garden arch by planting two rows 8-10 feet apart; bend and attach tree tops (leaders) over time to form a natural archway or hut.

Are Your African Violets Looking OK?

Posted by Hugh on January 14th, 2014

Sickly African violet plant

Healthy African violet plant

African violets (Saintpaulia ionantha) are easy to grow flowering house plants. Modern day varieties sold at supermarkets and plant shops often bloom 8-9 months a year.

Lighting needs are minimal, either from indirect sunlight from an east-facing window or under special “grow lights” 12 hours daily. African violets prefer water at room temperature (65-75 °F). Fill your watering container several days prior to watering to evaporate off fluorides and chlorides in the water.

Common problems with African violets are overwatering and fertilizer scheduling. Feed violets twice monthly, November thru February, with any brand “house plant” fertilizer. Use 1/2 the amount recommended on the package added to water. From March thru October, feed 3-4 times monthly with 1/2 rate solution. You must feed plants without burning roots with fertilizer salts. Once each month leach pots thoroughly, watering pots from above. Repot all plants once a year, generally in early autumn.

Water all plants at same time and never leave pots standing in water more than 1 hour. For old or large plants, a second watering may be occasionally needed as the roots fill the pot and need more. In general, interval between waterings may be 5-6 days. Waterlogged plants are an indicator of poor roots or bug infestations.

Check for mealy bugs. They often start out looking like debris (dust or soil) over the leaf surfaces and petioles. A mealy bug outbreak can build quickly. Applying rubbing alcohol to individual bugs with a cotton swab every 3-4 days should clean up an infestation within a month. Insecticidal soap, applied every 3-4 days, is also effective.

For Dry Sites Try Arizona Cypress

Posted by Hugh on January 11th, 2014

Cupressus ‘Blue Pyramid’ on ETSU campus in Johnson City, TN

Arizona cypress (Cupressus glabra) is silvery blue needled medium-sized evergreen (USDA hardiness zones 6 to 9). This southwest U.S. native demands full sun and excels in droughty, infertile, and well-drained soils. Conversely, Arizona cypress does not tolerate shade, poor air circulation and flooded soil. Arizona cypress is mostly disease and pest free unless too crowded in a landscape.

‘Blue Ice’, ‘Blue Pyramid’, and ‘Carolina Sapphire’ are three leading cultivars. The latter cultivar exhibits a silvery needle fine foliage, but may be northern hardy to zone 7. Depending on the cultivar planted, this upright branched pyramidal conifer grows rapidly to 30-50 feet high and 15-20 feet wide. An older specimen displays a rugged or furrowed trunk with reddish brown bark, a showy contrast with the silvery to steel blue foliage.

Whether planted as a single specimen or with several grouped together as a privacy fence or windbreak, the metallic needle foliage offers different foliage color with other conifer species. While needle color of some conifers may turn bronze or brown in winter, the silvery blue needle color seems to intensify.

Fall thru early spring are ideal times to plant Arizona cypress. Planting on a slope is highly recommended to avoid soils from becoming too soggy. This evergreen is not finicky regarding soil fertility or pH. Arizona cypress exhibits excellent drought tolerance once established for two years. Pruning is rarely necessary except to remove a wayward or broken branch.

‘Carolina Sapphire’ (left) and Cryptomeria

Shagbark Hickory

Posted by Hugh on January 8th, 2014

Shagbark hickory

Most tree lovers don’t plant U.S native shagbark hickory (Carya ovata) (USDA hardiness zones 4-8). Instead, they often inherit one when purchasing property. Shagbark hickory is notoriously difficult to transplant and grows very slowly in its early years. Like oaks (Quercus spp.) and beeches (Fagus spp.), hickories are long-lived, often standing tall in an open woodland setting for 200 years or more. Success with growing hickory is to not disturb its roots.

Shagbark hickory is a large tree, reaching 60-80 feet in height, but is capable of growing over 100 feet. Hickory grows naturally in moist well-drained river bottom soils although it is not uncommon to find hickory growing in a dry upland site.

Summer foliage is medium green and coarse textured. Leaves are alternate, pinnately compound, 8-14 inches long with usually 5 leaflets, sometimes 7. Each leaflet is 4-6 inches long and 1 – 2 ½ inches wide. Leaves stay mostly blemish-free until minor leaf spot diseases arise in late summer. Hickory is susceptible to a number of environmental stresses, including drought and hickory bark beetles. Over a 3-4 week period leaves color from bright gold to bronze before abscising in late autumn.

Male and female catkin flowers appear on the same tree in mid-spring and get little notice. Hickory nuts are a delicious food resource for humans as well as woodland inhabitants, including several bird species. The thin shelled round nuts are 1 – 1 ½ inches in diameter. Among nut lovers trees with sweet kernels and quality are tagged.

The grayish brown bark separates into thin curved plates, creating an overall “shaggy” appearance, hence the name “Shagbark Hickory.” Over the years large amounts of bark, leaf and nut debris may accumulate lots of litter. Hickory’s beauty far outweighs a little extra raking.

Hickory is a large shade tree suited for large properties, parks and golf courses. Winter gray shaggy bark and golden fall color are its major assets.

Moving Large And Mature Trees

Posted by Hugh on January 5th, 2014

Mature ‘Crimson Queen’ Japanese maple at Samara Farms Nursery, Nashville, TN

Perhaps tree lovers can’t plant wonderful trees such as shagbark hickory (Carya ovata), American beech (Fagus grandifolia), or white oak (Quercus alba). They can purchase property with the tree(s) growing on them. Most nurseries do not grow these difficult species or guarantee their success after planting. But, all is not lost!

Modern nurseries, backed by university research, have debunked many tree planting myths. For example, the recommended size and shape of a planting hole has changed. Digging a wide shallow hole is better than a narrow deep one.

Perhaps an old 100 year old Japanese maple may require a new home. There are specialty nurseries which are able to transport old mature trees hundreds of miles. We know more about how trees grow and the best time to lift and transplant one to a new hole several hundred miles away.

Some difficult to transplant trees can be moved during a narrow window of 4 to 6 weeks commencing in mid-winter. Digging is performed by a knowledgeable certified arborist and a specialty nursery with the proper equipment. These tree experts are listed on the International Society of Arboriculture (ISA) website: www.treesaregood.org

Some tree species are reputed to being difficult to move. Blackgum or tupelo (Nyssa sylvatica) is one such tree. Perhaps, this was true 50 to 100 years ago, but better cultivars have come along. Cultivars ‘Wildfire’ and ‘Red Rage are improved blackgum selections.