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Drought-Tolerant Plants for the Conscientious Gardener: Drought Survival for Your Garden

Parched earth photo courtesy of Flickr CC/Bert Kaufmann
photo courtesy of Flickr CC/Bert Kaufmann

In times of drought, limitations on the water supply usually go into effect. These restrictions can be challenging to the gardener. Water conservation in the landscape is one way to help our natural resources last. Don't wait for restrictions on outdoor water use, or worse yet, an outright ban. You can begin now to assess and improve your garden so that it becomes far more "water thrifty".

Site Inventory and Analysis

To conduct a site inventory and analysis with water conservation in mind, determine which plants have a high water demand. Learn the prevailing wind directions, patterns of sun and shade, existing topography and soil type on a site in order to improve growing conditions. Assess the condition and placement of your plants; do they conform to the principles of water use zones outlined below? Also, note existing large expanses of lawn and determine ways to minimize these areas to some extent if possible.

Create Water-Use Zones

A well-designed, water-conserving landscape is organized into three water-use zones: high, moderate and low. If water-demanding plants are spread throughout the garden, regroup them together close to the water source. The high-use zone should comprise the smallest area, such as a planting near the front of the home, where ornamentals are easily visible and near the water source. The largest numbers of plantings should be in the low water-use zone, where established plants need no supplemental irrigation. Drought-tolerant turf grasses, woody ornamentals and native or naturalized plants fit into this category. Moderate-use zones would include plants that need to be watered as they show signs of drought stress.

Landscape to Conserve Energy

Environmentally sound landscape techniques include planting for energy conservation and micro-climate improvement. For example, a house with southern exposure will benefit from the strategic placement of deciduous shade trees along the southwest corner. This lowers the amount of heat and glare received on summer afternoons. Existing micro-climates may be utilized to establish particular types of plantings; a garden in the shade is almost 20 degrees cooler than one in the sun. An area that receives sun only in the early morning will tend to dry out less, as the overall transpiration losses will be lower. 

Water Harvesting

Saving rainwater is a simple, water-wise idea. Connect downspouts from roof gutters to a plastic rain barrel equipped with a tap to save every precious drop of rainfall. The rain barrel will come with a top filtering screen to keep out leaves, twigs and very importantly mosquito larvae, which breed in standing water. Try to utilize this water as soon as possible to avoid larval breeding. To easily water your garden, attach a hand-held hose with a shut-off nozzle to the barrel's tap.

Water-Efficient Irrigation

Traditional sprinklers require high water pressure and waste almost 25 to 30% water due to evaporation and wind effect. Most existing water-wasteful systems can be refitted with low-flow components to deliver water precisely where it is needed - to the root area. With systems such as point/source drip, micro irrigation, drip line and soaker hoses, less water is wasted, moisture and nutrient uptake is maximized and soil-borne diseases can be reduced as leaf surfaces are kept dry.

Water-Wise Horticultural Techniques

Planting

  • Group plants together with plenty of room so their roots do not compete for water
  • Reduce size of water-thirsty turf areas
  • Introduce drought-tolerant species
  • Group plants according to their water needs

Watering

  • Water newly planted trees and shrubs as they are the most vulnerable to drought
  • Water early in the day to reduce water losses from evaporation
  • Water thoroughly - deep watering encourages deeper rooting
  • Water efficiently - low-flow watering delivers water precisely where it is needed

Maintenance

  • Amend soils to improve drainage and water-holding capacity
  • Use mulches to conserve soil moisture
  • Keep weeds down as they compete for moisture
  • Prune out all sucker growth, dead and dying wood and unwanted growth
  • Incorporate more "hard" landscape features, like patios, decks, fencing and garden structures to reduce large expanses of water-thirsty lawn
     

Further Suggestions

Designing for drought will help keep our green investments and natural landscapes alive. While some plant species are more xerophytic (better equipped to withstand dehydration) than most, others resist drought by slowing down the growth process. Oak, black locust, ginkgo, callery pear, Kentucky coffee tree and honey locust will slow growth considerably under drought conditions. Certain other trees, such as Katsura tree, shadblow, birch, moutain ash, yellowwood and flowering dogwood, have little drought tolerance.

Rosa rugosa has low water requirements
Beautiful Rosa rugosa has low water requirements

PLANTS WITH LOW TO MODERATE WATER REQUIREMENTS (*=native)

Shrubs

Botanical Name

Common Name

Water Requirement

Spirea japonica
spirea
moderate
Myrica pensylvanica*
bayberry
low
Viburnum prunifolium*
black haw
moderate
Cytisus species and cultivars
broom
low
Buddleja davidii
butterfly bush
low
Vitex agnus-castus
chaste tree
low
Rosa rugosa
rugose rose
low
Ilex glabra*
inkberry holly
moderate
Juniperus species and cultivars
juniper
low
Viburnum carlesii
Korean spice bush
moderate
Viburnum lentago*
nannyberry
moderate

Perennials and Herbs

Botanical Name

Common Name

Water Requirement

Artemisia species and other cultivars
artemisia, wormwood
low
Aster* species and other cultivars
aster
moderate
Gaillardia species and other cultivars
blanketflower
low
Rudbeckia fulgida*
black-eyed Susan
low
Asclepias tuberosa*
butterfly weed
low
Oenothera fruticosa
evening primrose
moderate
Liatris* species and other cultivars
gayfeather, dense blazing star
low
Echinacea purpurea*
coneflower
low
Rosemarinus officinalis
rosemary
low
Sedum species and other cultivars
sedum, stonecrop
low
Helianthus species and other cultivars
sunflower
low
Thymus species and other cultivars
thyme
low
Achillea species and other cultivars
yarrow
low

Annuals and Tender Tropicals

Botanical Name

Common Name

Water Requirement

Celosia cultivars
cockscomb
low
Cosmos bipinnatus
cosmos
low
Zinnia
zinnia
low
Sanvitalia procumbens
creeping zinnia
low
Senecio cineraria
dusty miller
low
Gazania cultivars
gazania
low
Pelargonium cultivars
geranium
low
Lantana camara
lantana
low
Tagetes cultivars
marigold
low
Portulaca grandiflora
portulaca, moss rose
low

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Noteworthy Books on Drought-Tolerant Plants