1 URBAN NEWSLETTER Winter Issue February 2003 James D. Walters, Jr., Piedmont Regional Urban

REPAIRING STORM DAMAGE

Ice storms and recent high winds have combined to break up a lot of . Bradford pears and other trees with tight crotches and included were hit hard. While a badly split is not repairable, broken branches can be remedied. In repairing broken tops, it’s important to understand the principle of Drop-crotch pruning. Drop-crotch pruning involves cutting a main branch or leader back to a lower crotch. The limb you cut back to should be at least 1/3 the diameter of the part that’s being removed. The critical part of making the cut, besides cutting back to a branch of sufficient diameter, is cutting at the appropriate angle. The proper angle is found by bisecting the angle of the branch bark ridge, and a 90° cut. The final cut should end just above the branch bark ridge. See the illustration below.

Certified know how to make proper drop-crotch cuts. For an up to date list of ISA Certified Arborists in you area, go to www.isa-arbor.com. Partially split trees can sometimes be repaired through the use of cables and reinforcing rods, but such repairs are expensive and not always effective. Specialized hardware should be used, according to ANSI A-300 specifications. Hardware store bolts and cables are not satisfactory. Cabling and bracing must be inspected annually and adjusted or replaced as needed. If a high-value tree needs to be reinforced with cables or braces, a Certified should be hired to install the hardware and maintain it annually. Cables and braces can be used to prevent splitting of bad crotches, but they are no guarantee against failure. Proper, preventive pruning of young trees is the best way to minimize the chances of storm damage. 2

FILLING CAVITIES

Forty years ago, filling tree cavities was an accepted practice. Good masonry in a tree hollow was almost an art form. The “tree expert” would excavate all the rot down to the sound , then either fill the void with concrete or close off the opening with brick and mortar. More recently, the industry decided that flexible, rubber bricks were the thing to use, since they would bend somewhat with the tree. Asphalt mixed with sand has also been used extensively. Fortunately, cavity filling has faded, along with flush pruning cuts and tree wound dressings. Occasionally, though, we run into a client (or a tree service practitioner) who insists that tree cavities must be filled in order to retard decay, or to deny access to animals. It’s up to us to educate them that filling cavities not only does not retard decay, it may (an probably will) accelerate it; and cavities in trees are valuable for animals other than squirrels. The accepted procedure for filling cavities involved removing decayed and discolored wood before adding the fill material. This frequently penetrated the tree’s protective chemical barrier, or compartment wall, allowing decay to spread further. An inflexible fill material, such as concrete, would then further abrade the wood as the tree swayed. Flexible fill materials, such as rubber or asphalt, did nothing to strengthen the tree, and provided a nice, moist environment for fungi. Tree cavities provide important shelter and cover for many animals, including flying squirrels, screech owls, bats, American kestrels (“sparrow hawks”), nuthatches, bluebirds, chickadees, swallows, flycatchers, martins, wrens, and the Prothonotary warbler. Closing off cavities does not hinder gray squirrel breeding—they just resort to leaf nests when cavities are not available. So how does one handle tree cavities? In most cases, it’s best to do nothing. A tree will seal over a small cavity eventually, and the tree’s reaction wood is stronger than anything we can put in the hole. Large cavities may never close, but as long as the tree does not sustain further damage, a basal cavity might not be a problem. A trained arborist can determine whether a cavity seriously weakens the structure of a tree. If an arborist determines that a tree is hazardous because of a cavity, then removal is usually the best solution. Tree cavities eventually show up in most broadleaf trees in our part of the world. Proper and timely pruning can prevent some cavities. We might have to live with others, and some will require removal of the tree. Filling of cavities, though, should be done by a dentist, not an arborist.

STAY AWAY FROM THOSE GUYS!

Guy wires, that is. For many landscapers, it is standard practice to use stakes and guy wires to stabilize newly planted trees. The guys typically consist of wire, with a loop of garden hose to cushion the tree. The wires are usually pulled tight to prevent the tree from swaying in the wind and possibly blowing over. Occasionally, installers even use turnbuckles to get the guy wires really tight. Although guys on newly planted trees were the state of the art thirty years ago, we now recognize a number of problems that result from their use. 3

Trees need to sway. As a tree flexes and bends in the wind, the growing tissues in the and branches adapt. This adaptive growth results in a tapering trunk, whereas a tightly guyed tree may develop little or no taper in the trunk. When the guys are finally removed, the trunk cannot handle strong winds. A tightly guyed tree might even break just above the guy wires in a strong wind or ice event. Another problem arises when the guy wires are not removed after a year. The guy wires can constrict the cambium and phloem tissues beneath the bark, stressing the tree by girdling. Trees often overgrow the wires, even with garden hoses, resulting in a weak spot in the stem. The problems with guys are easily avoided. If guys must be used, they should be made of a soft, flexible material, and should be slack enough to allow the tree to sway. The guys should be removed after the first growing season. A better idea, though, is being promoted by the University of Florida’s Dr. Ed Gilman. If a tree must be anchored, he recommends driving two untreated wooded stakes into the ground on either side of the root ball, to the side of the trunk. A third piece of wood is placed across the top of the root ball from one stake to the other, and attached to the stakes with screws. The untreated wood will decay in a year or two, so removal is not needed. There are no wires to trip pedestrians, and the tree is free to sway. For an illustration of Dr. Gilman’s tree anchoring method, visit the University of Florida’s web site at

http://hort.ifas.ufl.edu/woody/planting.

Once you’ve tried it, you’ll find that you no longer have any use for guys!

Newly planted trees can be anchored with two stakes, on either side of the root ball, driven into the soil. A cross piece is attached with screws or wires. Untreated wood should be used, so it will decompose and not need to be removed. This method eliminates the need for guy wires. On smaller trees, a single anchor is sufficient. The wooden anchor can be hidden with mulch, if desired. 4

THE SCHI TRADE SHOW

Myrtle Beach was the site for the South Carolina Industry conference and trade show. The three-day annual event is sponsored by the SC Nursery and Landscape Association. Exhibitors from the Carolinas, Georgia, Florida, Tennessee and elsewhere flock to the convention center to show off their nursery stock, equipment, and services. This year’s trade show was likely the largest ever. Here are some interesting plants being offered in the wholesale nursery industry this year: ‘Dynamite’ crapemyrtle—this medium to large-size crapemyrtle has bicolor flowers. The flowers begin as cherry-red buds, then open white with some red, later turning an intense red color. This variety should be cold hardy anywhere in South Carolina. Like other red varieties, it is probably not as trouble-free as the whites, but it would be a good choice where space is limited and bright color is desired. This patented variety was rare at last year’s show, but numerous growers are stocking it this year. Nuttall oak—this is the Quercus nuttallii you learned in school, but never saw in the wild (unless you’ve worked in the Mississippi River Valley). The tree is a fast- growing red oak, with potential to be a large tree. It looks very similar to Shumard and Pin Oak, but has better fall color than Shumard. Being a river bottom tree, it should adapt well to urban soil conditions. It is supposed to be more tolerant of pH conditions than pin oak. Nuttall oak tends to develop a strong central leader, without the annoying tendency to fork like some other species. Nurserymen should find it easy to grow, so it will probably be widely available soon. It was everywhere at the trade show. Bluff oak—Quercus austrina is native to SC, where it is found, of all places, on the bluffs along the Savannah River. The Florida grower who was promoting this tree was enthusiastic about its great fall color. This tree is a white oak, but not as large as Q. alba. According to Guide to Southern Trees, it prefers rich, moist soil near streams. It remains to be seen how it will fare in an urban setting, or in colder climates than Zone 8. This tree also goes by the rather unattractive name of Bastard White Oak. Two new cultivars of familiar oak species are the ‘Hightower’ willow oak and the ‘Highrise’ live oak. Both of these are cloned, own-rooted cultivars that should make really good trees without the forked leaders that are such a problem on seedling trees. They should be much easier for nurserymen to grow, too.

“SOUTHERN TREES” FACT SHEETS

The “Southern Trees” CD ROM has been around for some time, and is a bit obsolete when compared to “Horticopia,” with its color photos and all. The “Southern Trees” CD won’t even work on some of the newer computer operating systems. Still, the fact sheets were very useful, and being in black and white, they were easily printed and copied. There is good news: the 680 tree fact sheets are available over the internet at the University of Florida’s web site. The CD is not needed. Just go to:

http://hort.ifas.ufl.edu/trees/ and you’ll find the fact sheets. Dr. Ed Gilman, who developed both of the CD ROM programs, has lots of other good information and useful diagrams on the web site, so surf around and you’ll no doubt find some useful information.