HORTICULTURE
WATER WISELY
Xeriscaping and Plants for Dry Conditions
Julie Weisenhorn, Extension Educator
WHY IS IT IMPORTANT TO UNDERSTAND XERISCAPING?
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Increase in extremes - drought, flooding, cold, heat
Temperature trend is upward
Reduce dependency on potable water for yards & gardens
DEFINITION: XERISCAPING
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Xeriscaping: water-efficient landscaping
From the Greek word “xeros” meaning dry
Xeric plants: drought-tolerant plants
“Xeriscaping” is a term coined in Arizona where water was reduced by 50% for landscaping when
gardeners and designers chose xeric plants and employed water conserving methods of design and
implementation.
XERISCAPING: GARDEN STYLES
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Xeriscaping is not a new landscaping style
Historical garden styles reflect xeriscaping principles and ideas
Useful examples as we experience hotter summers and drier conditions.
1.
Islamic garden – Courtyards, water features, fruit trees, flowers, calligraphy on walls;
a. Water is a gift of mercy from Allah and a sin to waste it. Water is used to emphasize architectural
features, add movement and sounds, irrigate, humidify.
b. Influenced by: earlier people, the holy Qur’an, traditions of the Prophet Muhammed, the arid landscape.
c. Plants are used to create shade, shadows on architectural features
d. Gardens are placed to renew spirit and mind and offer respite from heat.
Patio garden - A Spanish garden style designed to offer sanctuary and seclusion, peace and shelter from hot sun,
heat; little or no plantable ground except for vines or maybe a single tree;
a. Four walls; invisible from the building; patio surface, containers
b. Provides a cool, quite retreat from urban life
c. Microclimate; provides opportunity to experiment with plants with marginal hardiness
d. Two distinct styes:
i. Andalusian (Spanish)
1. “Plantaholic” - crammed with plants
2. Water feature, stonework, wall-hung plants
3. Reflects the Moorish style
ii. Luis Barragán – Mexico
1. A harmonious extension of the home: “My house is my refuge and the garden is the
soul of the house”
2. Minimalist, simple, austere, uncluttered
3. Beautifully finished walls and stonework, adobe walls become a feature
4. Each element has a design purpose
5. Plants are elegant and play a secondary role to the “outdoor room”
Mediterranean garden
a. Fragrant, drought-resistant plants;
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Gravelly well-drained soil;
Plants that need little attention, little water and little nutrition (thrive better without).
Areas: California, South Africa, Australia, Chile
Three habitats
i.
Woodland – dominated by oaks and conifers
ii.
Marquis – dense cover of shrubby trees evergreen shrubs, small oaks and olives
iii.
Garrigue – sparse and open, aromatic shrubs, wild flowers, spring bulbs; grazing for sheep and
goats
Plants have evolved to complete their lifecycle before the heat of summer
Naturalistic
a. Tough, self-sufficient plant combinations
b. Thrive on difficult sites with minimal attention
c. Droughty lawn grasses (fescues)
Architectural features & material:
a. Terracotta – must-have (containers, tiles, roof tiles);
b. Wood - rough, rustic, rough-hewn
c. Stone / tile - loose gravels, cobbles, mosaics, steps and terraces
d. Colors – terracotta, rusty reds, brown-pink, ochres; whitewash, blue (northern Mediterranean);
red, orange, yellow, blue (Provence, France)
4.
Gravel garden
a. Sustainable, adaptable, low maintenance
b. Low-input - deep gravel suppresses weeds, conserves moisture;
c. Highly appropriate for small urban and suburban sites – especially for sites with construction soil
under topsoil.
d. Popular; emerged in 1980s garden design influenced by Modernism architecture of the 1930s and
Japanese garden design (Zen Buddhism – 12th century)
e. Extended outdoors to naturalistic gardens
f. Minimalist design
i.
Few, well-placed plants contrast with hardscape and are living sculpture - sculptural grasses,
topiaries, dramatic succulents
ii.
Gravel instead of lawn
iii.
Hardscape – colorful glass mulches, steel, polished concrete), up-ended rocks
5.
Naturalistic garden – An approach to garden design that mimics nature
a. Drought-tolerant plants – low fertility, low maintenance
b. Good drainage – sometimes raising planting areas
c. Soil preparation – increasing drainage using gravel or grit + OM
d. Highlight special plants using rock, openings / crevices, etc.
e. Dry creek / river bed using gravel + rock as your “river” or “creek”
6. Desert garden - Plants have adapted to desert growing conditions
a. Draw moisture from the air
b. Roots pull the plant underground to shelter tem from hot sun
c. Seeds germinate after heavy spring rains
d. Drop their leaves in response to falling temperatures, growing leaves again after rain
e. Spines reflect light and direct moisture to roots
f. Waxy leaf surface
g. No leaves and photosynthesize through their stems/trunks
h. Only open stomata at night
i. Store water in leaves, stem, roots or all three
j. Dense covering of wool, hairs, bristles to protect them from the sun
k. Barrel cactus can blow itself up and down like a balloon to regulate its surface area
l. Tight rosettes reduce the amount of leaf surface exposed to the sun
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Plants retreat underground (geophytes)
Root systems – long tap roots
Drop leaves, leaves adapted to water-loss
Tiny leaves with reduced surface area and thus transpiration
Thick waxy coating on leaves to reduce evaporation
Grey and silver leaves
Color reflects heat
Small hairs trap moisture - slow down evaporation and protect from drying winds
Aromatic essential oils that cool the plant while evaporating
Prefer droughty soils that well-drained and alkaline, low nutrients, full sun
Exception: French lavender – acid soils
Prune after blooming including lavender
XERISCAPING CONSIDERATIONS
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Planning & design
a. Function
b. Sun
c. time
Soil improvements
Appropriate turf areas
Low water-use plants
Efficient irrigation
Mulching
Proper maintenance
Water zones
1. Zone 1: Mini-oasis
a. Area nearest the house is where highest water-use plants should be located
b. Create the lushest plantings.
c. Lawn area
d. Coolest areas north and east
e. Area that receive run-off from your roof and down spouts.
2. Zone 2: Transition / Intermediate
a. Used to blend lush areas and drier parts of the landscape
b. Low to moderate water-use plants
c. Plants that require infrequent supplemental watering (1X per wk or less)
3. Zone 3: Arid
a. Farthest away from the house
b. Removed from most active areas
c. Most drought-tolerant plants
d. Natives and other varieties that rarely require supplemental watering
CONSERVING WATER
1. Choose and use drought-tolerant plants
a. Sedums
b. Natives
c. Plants with fibrous root systems
2. Harvest and use rainwater
a. Rain barrels
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b. Cisterns
c. Direct overflows
d. Measure water use
i. Rain gauges
ii. Rainfall reports
iii. Soil-moisture meters are helpful, but it’s best to get to know your soil, plants
Reuse water
a. Greywater: Check municipal and state statutes
b. May reuse water from cooking vegetables to water plants
c. Use mild, vegetable-based soaps
d. Pour around plants, not directly on them
e. Don’t use water with grease or oils, bleach or strong detergents
Conserve soil moisture, moderate soil temperatures and cool plant roots
a. Amend with organic matter (compost)
i. Herbaceous: 1-2” of compost, incorporated 6-8” deep.
ii. Woodies in a new bed: 4” of compost , incorporated 12” deep.
iii. Sandy soil - Increase water-holding capacity
iv. Clay soil – reduce compaction, improve drainage
b. Mulch plant roots
Reduce water waste
a. Hand watering directly at root zone
b. Irrigation
i. Gardens: locate drip hose locate on plant root zone
ii. Containers
1. Set up automatic irrigation for containers
2. Invert bottle reservoir or small flower pot sunk
iii. Lawns
1. Calibrate sprinklers and equip with timers
2. Turn off irrigation systems till grass looks dry equip with rain sensor
c. Trees
i. Water mature trees
ii. Create a moat and fill with water
Water in early morning
a. Water soaks in with minimal evaporation
b. Foliage dries off reducing fungal disease
c. Use an irrigation timer so you don’t have to get up early
d. Low water-use time for our communities
e. Less wind, cooler air temperatures
Water deeply and infrequently to encourage roots to grow deeply
Water the root zones, not the leaves
Prioritize watering
a. Annual containers
b. Young plants - seedlings, transplants, young trees, new shrubs
c. Fruits, vegetables
d. Plants that are not drought-tolerant
e. Lawns when they show signs of drought stress (wilt, dry, dull)
TECHNIQUES FOR COOLING A GARDEN
1. Water features cool and humidify a hot dry garden space.
a. Efficient recirculating pumps
2. Create shade to reduce solar heat
a. Shaded porch, pergola, gazebo
b. Tree canopy over seating area
c. Create shade with a canopy, umbrella, retractable awning
3. Use cool, reflective hardscape materials.
a. Tile
b. White, light-colored brick, stone
PLANT SURVIVAL STRATEGIES
1. Annuals flowers
a. Set seed quickly then die
b. Seeds germinate in fall rains, pause over winter (dormancy?) then start growing rapidly in
February.
2. Geophytes
a. Storage parts under underground
b. During growing season, add water and nutrients to storage parts, then upper dies in summer.
3. Double root system
a. Plant germinates, quickly grows long tap root with little growth above ground
b. Grows fibrous roots near surface that absorb any water and nutrients available
c. May have a symbiotic relationship with mycorrhizal fungi that helps plant take advantage of any
organic matter
d. Most dry-climate plants have roots 5x to 10x longer than their aerial stems.
4. Reduce transpiration
a. Photosynthesis uses carbon dioxide from the air
b. O2 is released along with some water vapor through the stomata.
c. Schlerophyllus (Grk. skleros ‘hard’, - phyllon ‘leaf’) plants have evolved that have leathery
evergreen leaves with a waxy cuticle on the upper surface.
d. In summer, transpiration is reduced to reduce water loss. However, transpiration is necessary
for growth as it powers the “pump” that carries nutrient-rich sap from the roots to the aerial
parts of the plant.
e. Scherophyllus plant go dormant during the summer. So best to plant these in fall when they are
starting their growth cycle (opposite of our cycle).
5. Reduce leaf surface / support
a. Summer dormancy – drop leaves
b. Reduce exposed surfaces
i. roll leaves
ii. shrink leaf size
iii. Leaf heliotropism - solar tracking behavior of plant leaves; orient leaves at an angle to
reduce sun heat (diaheliotropism)
6. Hairy plants, grey foliage
a. reflect light
b. reduces heat on leaf surface reducing evaporation
c. serve as a windbreak
d. create a microclimate over the stomata to conserve water vapor during transpiration.
e. Capture moisture from air - maintain coolness and humidity on plant’s surface.
7. Essential oils in plants
a. Produced by glandular hairs
b. Trap a film of air and acts as a barrier and limiting water loss from stomata
c. Evaporation of essential oils cools the environment around the plant
d. Protect its leaves from burning due to a rise in temp of the epidermis.
e. The stronger the plant’s scent, the more it is protecting itself from heat and sun.
8. Conserve water
a. Succulents: sponge-like interior that holds water
b. leaf arrangement shades other leaves
c. vertical ribs on stems shade and protect each other
d. Stomate close during the day and open at night (opposite of other plants)
i. CO2 is absorbed through stomata at night and fixed
ii. Then used at during day for photosynthesis without opening stomata
iii. No water loss through transpiration.
9. Salt will literally draw moisture out of leaves due to difference in osmotic pressure (pressure on either
side of the cell).
a. Plants grow low to ground to protect from salt, wind, etc.
b. Plants have waxy cuticles to protect leaves
c. Tough leathery leaves with hairs act as a windbreak
d. Plants will grow in a ball shape (close on itself) to protect itself from wind
e. To protect from cold, spiny xerophytes are small dense balls with spines to protect themselves
from wind and from browsers.
RESOURCES
Bennett, J., Dryland Gardening, Firefly Books, Ltd., Buffalo, NY. 2005.
Edwards, A. Gardening in a Changing Climate. Aquamarine, an imprint of Anness Publishing Ltd., London. 2011.
Filippi, O. The Dry Gardening Handbook: Plants and Practices for a Changing Climate, Thames & Hudson, Ltd., London.
2008.
Hamed, S., “Gardens of Islam”, Department of Landscape Architecture, Texas Tech University. http://z.umn.edu/15o9.
Accessed 05/02/16
The Complete Guide to Xeriscaping, City of Albuquerque, NM 1999
Seeley, M. WeatherTalk, http://climate.umn.edu/seeley/. Accessed 05/02/16
Seeley, M., “Understanding Earth’s Climate”, http://z.umn.edu/15o8. Accessed 05/02/16