| 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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