Posts Tagged ‘trees’

By Bill Seaman
All photos courtesy of Arborilogical Services, Inc.

Texas gardens are blessed to have a large variety of trees suited for our climate and soils.  If there is one group of trees where we might be short-changed, it is the conifers.  In the majority of the state, growing spruce, fir, and balsam is but a pipedream.  Between scorching summers and incompatible soils, many conifers struggle to survive a single season.  Even Japanese black pines, a staple in Texas landscapes since the 1960s, show a steady decline.  Masterfully marketed to be planted in threes, fives, and sevens, few of the odd-numbered plantings remain intact.  This year, we have seen the feathery, grey-green foliage of Leyland cypress turn brown and droop from a combination of heat stress and a fungal disease that has no successful management.  Another conifer is moved from the “To Plant List” to the “Don’t Plant List”.

The silver lining to be found in a year full of horticultural disappointment is to look for those trees, and particularly the conifers, that appear to take the stress unscathed.  They are there if you watch for them.  Some of these trees may seem to be old-hat, but are showing that they are trees that may deserve more respect than what they have been given.  Others are waiting to be discovered for what they can be.

Easily recognized by a combination of peeling and iridescent bark, Arizona Cypress trees create a special interest in the landscape.

Arizona cypress (Cupressus arizonica) best fits the first group.  Native to the Trans-Pecos region of the state, this conifer has worth in a landscape if only for its remarkable bark.  It has an exfoliating trunk that reveals an underlying tissue of copper, bronze and gold–iridescent colors rivaling those found on a butterfly’s wings.  Should you choose to add an Arizona cypress to your landscape, you will need to be patient to see the development of the showy trunk, as it is a moderate grower.

The light blue-green foliage of Arizona Cypress trees planted in the 1930s is giving way to recent cultivar introductions of grey and silver.

However, the nursery industry has rediscovered this tree’s importance, and has selected a number of cultivars based on an assortment of foliage colors that range from silver to blue-grey.  Mature Arizona cypress can be found in residential landscapes and park plantings from the 1930s and 1940s.  While their culture tolerates poor soils, Arizona cypress become their best when planted where drainage is nothing short of excellent.  Likewise, they need full sun from the day they are planted until they mature.

Well adapted to drought and high temperatures, California Incense cedar maintains its bright green foliage.

Waiting to be discovered is California incense cedar (Calocedrus decurrens).  Native to the more arid regions of Oregon, California, and western portions of Nevada, incense cedar is an almost unknown conifer that began proving itself in the Texas landscape more than 100 years ago.  Its bright green, scale-like foliage is soft to the touch, differentiating it from many upright junipers.  When mature, it produces a quirky drooping cone containing a single seed.  The bark is a reddish-brown and deeply furrowed.  In fact, the bark is so stylized, you might think the patterns of twists and turns inspired Van Gogh’s painting style.

California incense cedar is easily identified by its unique bark.

As a testament to its tolerance of extreme weather and pour soils, one of the oldest known incense cedars humbly stands in a Garland, Texas pioneer cemetery.  This tree has held its place for over a century.  California incense cedar is not readily available in garden centers, but nurseries that specialize in unique plants can order them for you.

Early Texas plantsmen recognized the similarities of our climate and soils to those of the European Mediterranean.  The introduction of trees that could adapt in Texas was the logical next step in their grand experiment.  As a result, we have Italian stone pine (Pinus pinea).

This Italian stone pines has developed a broadening canopy large enough to shade this two-story home’s roof and western exposure.

Known for its picturesque silhouette, this pine is suited for the thin rocky soils and infrequent rains that East Texas pines will not tolerate.  Mature Italian stone pines are somewhat lost in the summer urban canopies of San Antonio and Austin, but take their deserved place in the winter landscape.  As they grow, their shape morphs from a loose coned-shaped ornamental to a broad canopied shade tree.  Juvenile growth can be rapid, but the growth rate of mature trees is measured.  Winter hardiness of Italian stone pines has long been a topic of debate.  Young trees produce juvenile foliage of short, single bundled needles, which are completely uncharacteristic of the long paired needles of mature foliage.  It is believed that the juvenile growth does not have the same cold tolerance level as mature growth.  Should that be the case, it would make sense to plant nursery stock that has grown into its mature phase foliage.  Established Italian stone pines do grace Texas landscape as far north as Denton.

While this is only three trees to place on the “To Plant List”, the point is this:  Based on some simple observations, the list of conifers can be much larger than we might have first considered.

Bill Seaman is a sixth generation Texan, degreed horticulturist, and member of the certified arborist team at Arborilogical Services, Inc., “The Experts your Trees Deserve.”

Bryan White, a certified arborist with Arborilogical Services, Inc., was recently interviewed by NBC DFW.

The female moth actually lays the eggs on the underside of the leaf in early May after the tree leafs out.  The larvae hatch and build a web for protection, then begin to consume the foliage.  The webs expand as the worms increase their intake of foliage.  The feeding lasts about 2-3 weeks until they leave the tree and pupate.  The female emerges and the cycle can repeat 5 times a year requiring a different spray each time.  They do not move from tree to tree, as they only feed in the tree that the worms hatch from.  They generally cause no permanent damage, but we treat often because the client considers it a nuisance.

A Significant Root Pathogen

Ganoderma lucidum, the varnish fungus, is a pathogen that enters openings in root systems of many tree and shrub species. In our region, Red Oak, Cedar Elm, Pecan, Live Oak, Pears, and Photinia have all been reported to be species commonly infected by this fungus.

The entry points can be from any activity that damages or severs a plants root system. The fungus lives in the soil as a saprophyte, that is to say, it can live on dead organic matter with no ill effects until it encounters live roots that have been cut.

Published literature, archaic as it may be, suggests the fungus colonizes a plants root system slowly and may take several years, 10-20 has been proposed, to finally kill a tree or shrub. Some have theorized that is might just be a natural component of many old tree species.  We feel that it may be quite a bit more aggressive than first thought. Regardless of the pathogens history, it causes significant damage to our shade trees by destroying a trees structural root system.

Trees have two primary root systems. The structural root system is responsible for anchoring a tree to the earth. A trees fine feeder root system is responsible for the daily demands of moisture and nutrients. Once the structural root system has been compromised, a trees stability becomes quite a concern. Often, trees that fail during storms show evidence of colonization by Ganoderma sp.

The fungus will produce a fruiting structure, a fungal conk, near the base of the tree. It is a shelf like structure that varies in color from a rusty orange-red to a dark red with cream coloration almost always shiny in appearance. The concern is that once the fruiting structure is evident, the fungus has often destroyed a large part of the trees ability to stay anchored to the earth, thus creating a high potential for failure and a potentially dangerous situation.

The difficulty is that above ground signs can mimic other problems. Trees infected with Ganoderma sp. often leaf out in the spring with significant dieback and large dead branches with no changes in the trees environment. Tree owners will often report that the tree looked fine last fall. Even at this stage of the infection, there may be no visual evidence, a fungal conk, apparent at the base of the tree. There is also the opposite scenario in that a trees canopy looks perfectly fine, but fruiting structures have developed. In either case, further investigation may be recommended. These recommendations should never include anything that is proposed to help or control the infection. Recommendations should be to immediately investigate a potion of the trees below ground structural root system to determine the extent of structural root loss.

The sad conclusion is that there is no prevention or control once a root system has been colonized. There is obviously the avoidance of root damage of any type, which is very unlikely in the urban environment. The positive aspect is that after investigation, immediate removal is not always necessary. It does give your Certified Arborist a baseline mark to make appropriate recommendations regarding a potential timeline for removal and replacement.

This is not anything new to our urban forest, nor is it any type of epidemic that all susceptible tree and plant species will die from. It is a serious concern if a large.

by Kevin Bassett and Russell N. Peters

Dormant oil applications to trees and shrubs can be a quite effective tool when managing many of our insect and disease problems.

The application is done once a year during the dormant season. In our area this is roughly January through Mid March. Many times Dormant Oil applications are used in conjunction with other foliar sprays, such as fungicide sprays for the management of fungal leaf diseases. The Oil helps reduce the levels of pathogenic fungi that can “over winter” (survive) in bark fissures and leaf scales or unopened buds. The Oil alone does not provide control, additional spray applications with an approved fungicide will need to be done in the spring after the tree begins to leaf out.

Dormant Oil applications are quite effective against “over wintering” insect pests. Many of our early season pest problems can be reduced with Oil applications. We need to mention again that the Oil alone does not always provide complete management. Additional foliar applications with an approved miticide or insecticide may need to be scheduled for a complete management program.

A particular insect pest that Dormant Oil is especially effective against is the various scale infestations we get in North Texas. If you own Red Oak, Live Oak, Pecan, or Silver Maple, you can find one of the various scale species. Sometimes the level of infestation may not warrant an application. However, this pest can increase in severity quite quickly. Many times it’s best to include Dormant Oil applications as part of an overall health management program. Applications on an annual basis will help to keep scale populations below damaging levels.

The material is a very finely refined oil product, with practically no odor, which acts to suffocate the “over wintering” target pest. It is by far one of the safest products used in pest management.

Many times you may find us recommending the Dormant Oil application to include your shrubs. For example, there are a variety of scale problems which Oil applications can reduce, especially on Holly sp.

NOTE: If you own a swimming pool and we are applying Dormant Oil to trees and or shrubs near the pool, you may experience a cloudy look to the pool when we are done. This phenomenon is temporary and does not damage the pool or filter. It will dissipate in 24 – 48 hours. It is also completely safe to swim under these conditions as well.