Plant Answers  >  What is "Drought" and "Drought Stress"?

What is "Drought" and "Drought Stress"?
A List of Drought-tolerant Plants For Texas

In nature, water is usually the most limiting factor for plant growth. This is also the case in home or commercial landscapes. If plants do not receive adequate rainfall or irrigation, the resulting drought stress can reduce growth more than all other environmental stresses combined.


Drought can be defined as the absence of rainfall or irrigation for a period of time sufficient to deplete soil moisture and injure plants. Drought stress results when water loss from the plant exceeds the ability of the plant's roots to absorb water and when the plant's water content is reduced enough to interfere with normal plant processes. In Texas, plants may frequently encounter drought stress. Rainfall is very seasonal and periodic drought occurs. During drought, local governments may place restrictions on landscape irrigation in order to conserve water, and landscape plants may become subject to drought stress. The use of drought tolerant plants in the landscape can reduce the likelihood of plant injury due to drought stress.


How Does Drought Stress Affect Plants?

A plant responds to a lack of water by halting growth and reducing photosynthesis and other plant processes in order to reduce water use. As water loss progresses, leaves of some species may appear to change color -- usually to blue-green. Foliage begins to wilt and, if the plant is not irrigated, leaves will fall off and the plant will eventually die.


How Long Before Drought Stress Develops?

The time required for drought injury to occur depends on the water-holding capacity of the soil, environmental conditions, stage of plant growth, and plant species. Plants growing in sandy soils with low water-holding capacity are more susceptible to drought stress than plants growing in clay soils. A limited root system will accelerate the rate at which drought stress develops. A root system may be limited by the presence of competing root systems, by site conditions such as compacted soils, or by container size (if growing in a container). A plant with a large mass of leaves in relation to the root system is prone to drought stress because the leaves may lose water faster than the roots can supply it. Newly installed plants and poorly established plants may be especially susceptible to drought stress because of the limited root system or the large mass of stems and leaves in comparison to roots.

How Does Environment Affect Drought Stress?

Aside from the moisture content of the soil, environmental conditions of high light intensity, high temperature, low relative humidity and high wind speed will significantly increase plant water loss. The prior environment of a plant also can influence the development of drought stress. A plant that has been drought stressed previously and has recovered may become more drought resistant. Also, a plant that was well-watered prior to drought will usually survive drought better than a continuously drought-stressed plant.


What Changes Can Be Made to Reduce Effects of Drought in the Landscape?

The landscape environment can be modified to reduce or prevent drought stress by irrigation, mulching, and providing shade. Reducing the overall water requirements of the landscape is best achieved by initially designing the landscapes for water conservation, including efficient irrigation systems, proper watering and the use of drought tolerant plants where appropriate.

What are the Characteristics of Drought Tolerant Plants?

Some species have an inherent tolerance of drought because they have evolved in arid areas, regions with frequent drought, or regions with soils of low water-holding capacity. Some species have anatomical or physiological characteristics that allow them to withstand drought or to acclimate to drought. All plants have a waxy coating on their leaves called "cuticle," but some species have developed exceptionally thick cuticles that reduce the amount of water lost by evaporation from the leaf surface. Leaf hairs, which reduce air movement at the leaf surface, are another means of reducing evaporation from the leaf. Since the amount of surface area exposed to the atmosphere affects evaporation, leaf size and thickness are other adaptations, with thicker leaves and smaller leaves being more resistant to water loss. Some species have evolved large surface root systems to quickly absorb rainfall, while other species grow deep root systems to tap deep water tables. Some plants avoid drought by dropping their leaves during droughts, and quickly regrowing new leaves when environmental conditions improve.

Lists of Drought Tolerant Plants

The plants listed tolerate drought stress better than most landscape plants. Although these plants are considered drought tolerant, new plantings will require regular irrigation for 6 weeks to 6 months or more before they become established well enough to be effectively drought tolerant. Trees larger than two inches caliper will take longer
to establish.

Plants are listed by common and scientific names (alphabetized by scientific name) and are divided into categories such as trees, shrubs, groundcovers and vines. Those marked with **** are considered to be Deer
Resistant also. Remember that all plants brought into the landscape
which are
thought to be deer resistant MUST be protected from deer for at least three months
after planting to avoid "curious or hopeful feeding by the deer".
This can be
accomplished by the use of a repellent such as Liquid Fence or by installing a
physical barrier or fright device (such as a motion sensor water sprinkler). No trees
are so marked as all are vulnerable until they reach a size sufficient to withstand the rubbing of the buck deer.

===================================
===================================

Drought Tolerant Trees

Common Name Scientific Name
---------------- --------------------

Pecan Carya illinoensis

Cedar Cedrus spp.

Texas Redbud Cercis canadensis 'Texensis'

Citrus Citrus spp.

Persimmon Diospyros virginiana
Oriental persimmon Diospyros kaki

Loquat Eriobotrya japonica

Guava, Pineapple**** Feijoa sellowiana

Yaupon,
yaupon holly Ilex vomitoria

Crape myrtle Lagerstroemia indica, L. fauriei, L. (indica X
fauriei)

Wax myrtle Myrica cerifera

Olive Olea species

Avocado, Mexican Persea americana var. drymifolia Blake

Japanese black pine Pinus thunbergiana

Pistachio Pistacia species

American Plum Prunus americana

Pear Pyrus species

Shumard oak Quercus shumardii

Live oak Quercus virginiana

Mountain Laurel Sophora secundiflora

Bald Cypress Taxodium distichum

Jujube Ziziphus spp.

========================================

Drought Tolerant Shrubs

Common Name Scientific Name
---------------- -------------------

Glossy abelia Abelia x grandiflora

Century plant **** Agave americana

Aloe Aloe

Japanese barberry Berberis thunbergii

Butterfly bush Buddleia spp.

Cactus **** Cactaceae family
Some Species

Bottlebrush Callistemon spp.

Dwarf natal plum **** Carissa grandiflora 'Prostrata'

Pampas grass **** Cortaderia selloana

Cotoneaster Cotoneaster spp.

Pineapple guava Feijoa sellowiana

Fig Ficus carica L.

Kumquat Fortunella japonica

African daisy Gamolepis chrysanthemoides

St. John's-wort Hypericum spp.

Yaupon, yaupon holly **** Ilex vomitoria

Juniper **** Juniperus spp.

Lantana **** Lantana spp.

English lavender Lavandula angustifolia

Texas sage **** Leucophyllum frutescens

Agarita **** Mahonia trifoliolata

Wax myrtle Myrica cerifera

Oleander **** Nerium oleander

Prickly pear **** Opuntia ficus-indica

Pittosporum Pittosporum spp.

Plumbago **** Plumbago auriculata

Pomegranate **** Punica granatum

Pyracantha Pyracantha spp.

Indian hawthorn Raphiolepis spp.

Rose Rosa spp.

Rosemary **** Rosemarinus officinalis

Texas Mountain Laurel **** Sophora spp.

Spiraea Spiraea spp.

Yellowbells, Gold Star Esperanza Tecoma stans
Cup of Gold (Cupea de Oro)

Blueberry, Sparkleberry Vaccinium spp.

Viburnum **** Viburnum spp.

Chaste tree, 'Texas Lilac' Vitex**** Vitex agnus-castus

Yucca **** Yucca spp.

================================================

Drought Tolerant Groundcovers

Common Name Scientific Name
---------------- ----------------

Bermudagrass **** Cynodon dactylon

Daylily Hemerocallis spp.

St. John's-wort Hypericum spp.

Morning glory Ipomoea spp.

Juniper **** Juniperus spp.

Lantana **** Lantana spp.

Liriope Liriope spp.

Rosemary **** Rosemarinus officinalis

Blackberry Rubus spp.

Purple heart Setcreasea pallida

Cape honeysuckle Tecomaria capensis

Asiatic jasmine Trachelospermum asiaticum

Society garlic **** Tulbaghia violacea

Zoysiagrass **** Zoysia spp.

==========================================

Drought Tolerant Vines

Common Name Scientific Name
---------------- ----------------

Crossvine Bignonia capreolata

Bougainvillea Bougainvillea spp.

Trumpet creeper Campsis spp.

Creeping fig **** Ficus pumila

Carolina yellow jasmine**** Gelsemium sempervirens

Morning Glory Ipomoea spp.

Honeysuckle Lonicera sempervirens

Virginia creeper Parthenocissus quinquefolia

Cape honeysuckle Tecomaria capensis

Confederate jasmine Trachelospermum jasminoides

Grape Vitis spp.
Grape, Muscadine
Grape, Mustang
Grape, American


 


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