The Post Oak’s “Roll” in the Cross Timbers Region
The gently rolling native grasses of the Fort Worth Prairie once stood between the two Cross Timbers. Settlers wrote of stark transitions from the prairies to the forests, describing them as “walls of woods”. Post oaks invaded the Fort Worth Prairie about the same time we did. Through the suppression of fire, agriculture, and ranching, the abrupt transition has been blurred by an invasion of woody species into the grassland. Many groups of post oaks and black jack oaks grow in Fort Worth where there was once only prairie or savanna. As the oaks matured, their canopies closed and they shaded out the native grasses reducing the fire fuel load. Post oak may have been well suited to survive the rigors of the Cross Timbers or an effective opportunist at invading the prairie. However, it has not faired as well in modern urban developments. Post oak cannot tolerate root disturbance. The tree grows so slowly it is unable to heal torn and ripped roots before they decay. Many post oaks die in patches without apparent cause. Dr. Dave Appel, Associate Professor of Plant Pathology and Microbiology at Texas A&M University, has conducted some interesting studies on post oak decline. He discovered that much had to do with the depth to hardpan. Hardpan is an underground impermeable layer that is associated with water table depth. Since Cross Timbers post oaks grow under arid conditions in well-drained soils, trees over shallower hardpans have water that is more available during prolonged droughts. Trees less than a few hundred feet away that have a deeper hardpan may not be able to survive. Dr. Appel also found just the opposite was true in urban areas. Post oak is one of the least tolerant species to flooding. Post oaks over shallower hardpans will be more susceptible to over watering than those over deeper hardpans. A new water loving homeowner, a new irrigation system, or a recent change in drainage patterns can be enough to tip the scale. Post oak death due to over watering will have similar symptoms of trees with other types of root damage. Tips of branches will die back causing an abundance of epical sprouting (sprouting of small twigs along trunk and/or major limbs). Trees with root damage often take several years to die. As the tree consumes its starch reserve, it will produce fewer and smaller leafs while branches will continue to die back. As the tree uses up the last of its energy reserve, death can appear to happen suddenly after a flush of growth in the spring or acorn production in the fall.
You are fortunate indeed if you have a post oak in your yard. Because of their slow growth rate and their difficulty surviving transplanting you will never find one at a nursery. Your tree successfully took hold in the arid grassland or cross timbers and grew slowly and steadily. It was one of the lucky few that survived construction and it provides an abundance of shade for you and food for urban wildlife. If you are lucky enough to have a post oak under your care, like a cactus, it will be healthier if you simply ignore it. Don’t over prune it or feed it, and avoid putting flowerbeds or driveways under the canopy where you will disturb its roots. Just enjoy its beauty and its shade. When your neighbor’s exotic imported trees are wilting in the hot Texas sun, you’ll be as happy as your post oak with your reduced water and electric bill.
The morning of Friday, December 15, 2017, three Citizen Foresters and several other volunteers from the Master Gardeners program planted 16 trees in Arlington. The species planted were cedar elm, bur oak, bald cypress, desert willow, and Mexican plum. Although the morning began with chilly weather, volunteers worked tirelessly, and soon the sun rose over the treetops onto four trees that had already been planted. Thanks to the efforts of the volunteers and the forestry staff, all 16 trees were planted by 10 a.m. The event was coordinated between the City of Arlington, Citizen Foresters, and Master Gardeners with the help of local resident Juliet Bran.
The trees were planted on the median of Shorewood Drive near Bowman Springs Park in Arlington. This street had only a few existing post oak and cedar elm, but will now be able to grow to provide a full tree canopy and beautify this residential street.
Loyd Park, Grand Prairie
September 22, 2017
Make plans to join us for our annual membership meeting. Everyone is invited to have lunch, review the year that was and vote on a new Executive Committee. After the business meeting, you can enjoy the hiking trails, rent a kayak or canoe, or make an evening of it by reserving a cabin or campsite. Loyd Park is located on the western shore of Joe Pool Lake in south Grand Prairie. Admission if free just say you are with Cross Timbers, everyone will meet in Loyd Lodge. Click on the map for more information about Loyd Park.
Let us know you are coming by registering on Eventbrite
Please Support Us!
Cross Timbers Urban Forestry Council
2018 Urban Forestry Conference
February 1, 2018
Arlington Convention Center
1200 Ballpark Way
Arlington, TX. 76011
The Crosstimbers Urban Forestry Council and Trinity Blacklands Urban Forestry Council are teaming up with North Texas Nursery Growers for the 2018 conference. This collaboration will allow attendees to continue to have the top notch class that everyone is accustomed to and access to North Texas Nursery Growers trade show. More information coming soon.
Emerald Ash Borer: The Ash Nightmare
By Rachel Murray
Many US cities are preparing for an Emerald Ash Borer, Agrilus planipennis (EAB) invasion. The EAB is native to northern Asia, but was discovered in Michigan and Ontario in 2002. The adult EAB has a bright outer metallic green color, with copper colored abdominal. It is roughly half an inch long, and only one eighth of inch wide. The EAB larva is milky white with bell shaped segments. Since it is discovery it has spread to over 25 states and most of eastern Canada. The invasion continues to move west. Already 70 million ash trees have been infected and there is a chance of losing a large percentage ash trees in North America. East Texas has already been affected by the EAB. There is a chance that EABs will travel to the DWF metroplex.
You can easily identify if your tree has been infected or not. When an EAB larva bores in to an ash tree, they create a winding S shape path, called galleries. These galleries become visible when the bark begins to split. If your tree is infected, callous tissue will start to form causing the bark to become weak. Another thing to look out for is D shape holes. After they become an adult, the EAB exits the tree and create the hole. You can recognize if your tree has been infected by checking for the S shaped galleries and D shape holes. A citizen can also observe if the tree has been infected by watching for epicormic shoots. Epicormic shoots are small shoots that grow from previously dormant branches. If you can identify these factors on your tree, it is likely it has been infected and needs to be treated.
There is multiple ways for you to prevent the invasion of EAB. Most time if an ash tree gets infected it will die in 2-3 years. At this time it would be helpful for you to remove your tree and replace it with another species. As a citizen you can also spray/inject pesticides for your ash tree. You will have to do this annually, but most the time is will protect your trees from the EAB. To reduce the spread of EAB larvae, do not bring any firewood or ash wood into the area. Even after a tree is cut down the EAB larva can survive and continue to infect the area. Also when you do store firewood, be sure to always keep it away from existing trees, in case of any other pests.
Being observant of signs and knowing the prevention’s can help us stay protected from the emerald Ash Borer.
IT’S A TREE’S LIFE!!
by Cheryl Bourne Netto – copyright © June 2017
Have you ever given thought
To the benefits that are brought
By those majestic living statues that are trees?
We may take them for granted
Not knowing how they were planted,
Decorating outdoor space with such grace.
Summer landscapes would be boring
Without these giants with limbs soaring
Displaying a palette of magnificent hues.
Some stand like honor guards
On either side of great, long yards
Leading to grand estates and stately mansions.
A welcome haven for our feathered friends
Many a bough and branch surely lends
A cosy roosting place at the end of day.
Leafy crowns reach out to the sky
As if to touch clouds passing by
While oxygenating the air for our well-being.
Mahogany, teak, cedar, oak, maple and pine
Are some types of trees that we may find
Are used for crafting beautiful furniture pieces.
For Christmas trees the fir is preferred
And by children even perhaps revered
When sparkling with fairy lights and colored balls.
Graceful palms tower protectively over a tropical scene,
Evergreens persevere through the winter in green
Wispy willows weep until the autumn, it seems.
Paper, firewood, planks and housing material too
Are some other uses trees are put to,
Not least of all providing necessary shelter and shade.
There are so many useful purposes that trees serve
And for that much appreciation they deserve.
They are a natural resource which redounds to our benefit.
Providing food and employment while preventing soil erosion,
Shielding ultra-violet rays and cutting down noise pollution,
Without this vital natural resource what would we do?
Mother nature cooperated and the predicted storms held off long enough to complete our spring Tree Tour. Over 20 people spent the day visiting some of the most notable trees in the region. Some were historic, some were really big and some were just odd! Local arborist Wes Culwell designed the tour stops and had a wealth of information on each tree visited. The day started with a stop at a giant post oak tree where Sam Houston camped while traveling through North Texas and ended with a live oak in Lake Worth that was saved from destruction when the highway was expanded. This tree is currently being cared for by a group of local patrons! Also thanks to the City of Grand Prairie for providing vans and drivers for transporting the tour participants.
Courtney Blevins, CF, CA
Texas A&M Forest Service
Ft. Worth Regional Forester