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Monday - October 31, 2011

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Drought Tolerant, Trees
Title: Trees and shrubs turning brown in Dripping Springs TX
Answered by: Barbara Medford

QUESTION:

Due to the extended drought - a number of trees and shrubs in our Dripping Springs area property have turned brown. Specifically: Live Oak; Agarita; Ash Juniper; Cedar Elm. Is this a dormant stage due to low water? Or is it likely that they will not recover?

ANSWER:

This is a question we are getting fairly frequently from all over the Southwest and one to which we really do not know the answer. A lot is dependant on whether we get some substantial rains soon, how hot it is next Summer and whether the stressed trees are susceptible to disease. From our Native Plant Database, we will extract some comments on each that might be informational:

Quercus fusiformis (Escarpment live oak):Note the warning about drought-stressed trees being prone to contacting Oak Wilt. Be careul to avoid damaging the bark of the oak trees and prune only in the coldest part of the Winter, painting the pruning wound of any branch larger around than your thumb with pruning paint.

"Ranging from the Glass Mountains and Arbuckle Mountains of southern Oklahoma south through the center of Texas to the mountains of Coahuila, Tamaulipas, and Nuevo Leon in Mexico, Quercus fusiformis is the common live oak used in landscaping and found in the wild in central Texas. It is more drought-tolerant and cold-hardy than Q. virginiana, which it is sometimes considered a variety of. Like Q. virginiana, its magnificent, stately form has endeared it to generations of residents and it remains popular to this day. Also like Q. virginiana, it is susceptible to live oak wilt and live oak decline when stressed by drought, so care must be taken to protect it from injury both aboveground and below ground to prevent infection."

Mahonia trifoliolata (Agarita): This plant is native to this area, and is considered drought tolerant.

"Water Use: Low
Light Requirement: Sun , Part Shade
Soil Moisture: Dry , Moist
Soil Description: Rocky, limestone soil.
Conditions Comments: This evergreen shrub has rigid, spreading branches often forming thickets. Gray-green to blue-gray, trifoliate, holly-like foliage has needle-sharp tips. Clusters of fragrant, yellow flowers are followed by red berries from May to July. Songbirds eat the fruits, and quail and small mammals use the plant for cover. It is considered a good honey source."

Juniperus ashei (Ashe juniper) - although often hated because of the seasonal pollen allergies, this is a very sturdy drought-tolerant tree.

"Ashe Juniper is native, it has been abundant since the earliest European explorers arrived (and likely longer, given evidence that it has been in Texas since the Pleistocene), and it is an integral part of the native flora. The uniquely rich and well-draining soil that builds up as juniper leaves fall and decompose is ideal for several native plants, some of which tend to occur almost exclusively in association with it, including Cedar Sage (Salvia roemeriana) and Cedar Rosette Grass (Dichanthelium pedicillatum). The beautiful but notoriously difficult to propagate Texas Madrone (Arbutus xalapensis) also seems to germinate best in the soil beneath these trees."

Ulmus crassifolia (Cedar elm) - often considered an East Texas tree, this one nevertheless does well in Central Texas, and is drought-resistant.

"Water Use: Medium
Light Requirement: Part Shade
Soil Moisture: Moist
CaCO3 Tolerance: Low
Cold Tolerant: yes
Soil Description: Moist to dry, alkaline soils. Sandy, Sandy Loam, Medium Loam Clay Loam, Clay, Caliche type, Limestone-based
Conditions Comments: Cedar elm is a nicely-proportioned, hardy, drought tolerant shade tree for a broad range of soil types. It brings vivid yellow color to the landscape in autumn. No need to rake the small leaves—they compost nicely. Young trees have corky wings on their branches. The Mourning Cloak and Question Mark butterflies use it for larval food. Withstands drought and heavy, infertile soils. Susceptible to Dutch elm disease. Reasonably fast-growing. Known to cause severe allergy reactions."

Bottom line: The natural reaction to heat and drought in plants is to curl their leaves to conserve moisture. Leaves may turn brown and even fall off early in extreme heat and drought. Nevertheless these trees have, genetically speaking, seen all these conditions before over the centuries that they have survived in Central Texas. Some trees may very well be lost, which is probably Nature's way of avoiding expenditure of resources on weakened trees. We certainly would not destroy any trees until they have the opportunity in Spring to begin leafing back out. The roots of these trees have food and moisture stored up to sustain the tree through hard times. This is the core reason Mr. Smarty Plants insists on plants native not only to North America but to the areas in which those plants grow naturally-they have survived extreme conditions before, and will again.

 

 

 

 

 

From the Image Gallery


Escarpment live oak
Quercus fusiformis

Agarita
Mahonia trifoliolata

Ashe juniper
Juniperus ashei

Cedar elm
Ulmus crassifolia

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