Study Guide 1 - Southwest Trees and Shrubs
Southwest Home Gardening
Climate is the key to southwest gardening. Our climate ranges from subalpine to subtropical
deserts, so a wide array of landscape trees and shrubs can be grown in Southwest. Very few
landscape trees and shrubs grow well over the entire range of climates found in the region.
Therefore, it is important to know how local climate influences the types of plants that can grow
in the region. Many climatic factors play a role in determining the kinds of plants that will grow
in a given location. Some of these factors include geography, minimum winter temperature and
maximum summer temperatures, rainfall amount and distribution, humidity, day length and light
intensity. The Sunset climate system divides the Western United States into climate zones and
then lists many landscape plants and what zones they grow best in.
Leucophyllum Frutescens or Texas Ranger
●Medium to large, mostly evergreen shrub
●Native to the Chihuahuan Desert located in the South Texas and Northern Mexico
●Go- to shrub when designing a southwestern, desert - style landscape
●6 - 8 feet tall with a similar width
●Covered with short, light gray hairs on leaves called tri - cones
●Magenta to lavender colored flowers at the end of the shrub’s stems
●Prune heavily once a year in March
●Water only during the summer
●No extra water required in the winter
Bougainvillea
●Woody shrubs
●Tropical and semi - tropical
●Common in hot, arid, and Mediterranean cities around the world
●Hybrid mixture of genus Bougainvillea and some are from South America
●Frost sensitive, where leaves and stems are easily damaged in Phoenix by winter
temperatures lower than 32 degrees Fahrenheit
●Colorful white, pink, red, orange, salmon, magenta, and purple flowers are modified
leaves called bracts
●Bracts surround the base of very small, white, inconspicuous flowers
●Some plants have multicolored flower bracts or variegated foliage, such as Raspberry Ice
●Hybrid selections range from growth habits, from dwarf to compact, to large and
sprawling with arching, vine - like stems
●Climbs up with structural support
●Leaves usually obscure sharp, stiff spines and can cause injury if mishandled
●Not recommended to be near walkways
●Provides accents and compliments landscapes in the desert southwest
Lantana
●Quintessential oasis, landscape shrubs in the desert southwest
●Common and scientific name
●Hybrid mix of 2 lantana species from South America
●Evergreen shrub with aromatic foliage with a sandpaper texture
●Accent throughout the warm temperatures
●White to yellow, orange, pink, red, and purple
●Upright or low as a ground cover
●Gold Mound have a mounding habit of growth as a low growing plants to cover the
ground, hang in patio baskets, or in pots as accents
●Lantana Montevidensis or the Purple Trailing Lantana
○Can be used as a ground cover as a mixed landscape design setting
○Can be damaged in temperatures lower than 32 degrees Fahrenheit
○Quickly recover and regrow in the warmer weathers
○Durable plant responds well to pruning
○Easily managed year round by applying consistent water during the summer
○Versatile
Nerium Oleander or Oleander
●Most common in the southwest desert
●Originated from the Mediteranean region
●Ornamental shrub
●Dense canopy of 4 - 6 inch evergreen leaves that tolerate the strong sun and heat during
the Arizona desert summers
●Evergreen
●Heat tolerant
●Freeze sensitive and will occasionally suffer damage below 25 degrees Fahrenheit
●Profuse Blooms
●Fast growing
●Low - maintenance
●Heavy bloomers
●Fragrant plant
●White to deep wine red flowers
●March through September
●Depends in height and width
●5 feet to 20 feet
●Summer accent plant, hedge, or screen
●Pruned and trained through consistent maintenance
●All parts are POISONOUS
●Contact to the skin will cause irritation
Hesperaloe Parviflora (scientific name) or the Red Yucca (common name)
●Belongs to the Agave family
●Neither a true yucca or aloe
●Native to the Chihuahuan desert areas, including Mexico, Texas, and New Mexico
●Staple accent plant in xero or dry landscape gardens throughout the Phoenix Metropolitan
area
●Grows semi - stiff, strap - like leaves from the ground in relatively small but upright
clumping or rosetting form
●Mature shrubs range in height from 2 - 4 fee, depending upon water availability
●In the spring and early summer months, they adorn themselves with a dense array of
flower stalks from 6 - 8 feet tall covered in numerous coral pink to red, tubular flowers
●Usually holds wildlife
●Small birds
●Attracts hummingbirds
●Floral nectar is provided within the flowers
●Little water and pruning care
●Merely remove flower stalks at the root
●Never shear
●Cannot regrow in a natural and healthy form if sheared
●Low water use
●Heat and cold tolerant
●Accent plant
●Easy maintenance
●Attracts wildlife
●Can be seen planted in roadway medians, shopping center parking lots, and along
highways
●Vital to the landscape
●Provides food and habitat for many animals
●Provides color, form, and texture
Notes - Video - Landscape Trees
●Defines place and relationship with nature (sense of place)
●Vital to health and beauty of the cities
●Provides shade
●Reduce local ambient temperatures
●Produce oxygen
●Mitigate city pollution
●Provide food and habitat for animals
●Grace us with sculpture and beauty
Prosopis or Mesquite Trees
●Taxonomic genus prosopis
●Iconic element for water conservation
●South America to Texas to Arizona
●More wide spreading, open and tall
●Feathery and firm - like leaves that conserve water and prevent from overheating
●Grayish to reddish brown bark on trunks become tough, rough, and ragged during the
summers
●Common for cooking, smoking fine meats on a barbecue, and burning for heat
●During March and April, green creamy catkin flowers grow followed by 3 - 5 inch long
light brown pods that fall off in the middle of July
●Edible pods and provides food
●Valuable and nutritional food source
●Versatile landscape trees
●Summer shades for parks, resorts, civic spaces, and other naturalized areas
●The growth habit and size is unanticipated by homeowners
●Rapid growth rate
●If heavily watered, can grow up to 40 feet tall and spread to up to 80 feet
●Horticultural error if not taken into account with size
●Subject to unbridled packing (mesquite versus man)
●Prune unruly branches which may cause additional problems including wetwood, a
bacterial disease
●Adaptive
Parkinsonia Florida or the Blue Palo Verde Tree
●National state tree of Arizona
●Spanish phrase for “green stick”
●Sonoran desert habitat
●Greenish - blue bark, trunk, and branches
●Naturally rounded form and grow full, rounded canopies
●Shrub like appearance
●Raise the crown and remove the lower branches to provide a tree - like form
●May cause bacterial diseases known as wetwood
●Handle with care
●Open and wide - spreading form
●Grows as tall as 30 feet tall and as wide as 50 feet
●Grows more profusely when it rains
●Sparsely distributed with bluish green leaves and stems that have chlorophyll that process
carbon dioxide into sugars through photosynthesis
●Photosynthetic branches and leaves
●Red and lemon flowers cover the canopy of the tree during the arrival of spring
●Brown pods cover the canopy of the tree and fall during mid - July/summer months
●Wildlife food source with pods
●Grows in the most extreme environment (like Arizona’s desert)
●Best in large - scale landscapes with other desert - adapted landscape plants in the
Sonoran desert
●Not in parking lots as it needs room to grow
●Mature trees are large and provide shade
●No invasive pruning required
●Foundational part of rugged Arizona
Olea Europaea or the Olive Tree
●Relatively small, many - branched evergreen tree that grows best in a Mediterranean or
hot desert climate
●Archaeological evidence suggests that olive trees were domesticated by people as early as
10,000 years ago
●Closely associated with human religious, cultural, medical, and food traditions for
thousands of years
●Some specimens are many centuries old
●Drought and heat tolerant
●Desert - adapted
●Irregular and spreading form
●Similar to a very large shrub
●Asymmetrical and free - spirited
●30 - 50 feet tall with similar width
●Have multiple trunks and can be trained to have a single trunk with persistent effort
●Very old olive trees provide a trunk flare (timeless art with picturesque aspects)
●Grayish green on the top and silver on the underside
●Light reflects off of the leaves, especially in the wind that provide depth to the canopy
●Springtime respiratory allergies
●Plant sterile tree cultivars
●Olive fruit litter
●Only sexually sterile trees can be planted to prevent allergies
○City in Arizona have banned the landscape planting of olive trees
○The dropping fruit is messy and staining on hard surfaces
●Basal suckering and branching
○Basal suckers can lead to landscape oddities
●Needs little care if a natural landscape is preferred
●Strong - willed olive
●Brutally subjected to pruning calamities and sculptures
●Iconic persona Mediterranean garden motif
●Prominent in older Phoenix neighborhoods
●“Legacy” trees
Dalbergia Sissoo or Indian Rosewood
●Native to the Indian subcontinent in South Asia
○Economically important
○Wood is harvested for furniture, cabinetry, and musical instruments
○Foliage is used to feed livestock
●Evergreen with a dense canopy of bright green leaves
●With ample irrigation, can grow large to up to 60 feet tall
●Trunk grows in a crooked manner with asymmetrical canopy
●Bright evergreen aspen - like foliage
●Light colored bark that is light and fissured
○Textural element
●Copious fragrant, small white flowers
●Light brown seed pods that drop to the ground during the late summer and fall season
●Growth quickens in the heat of July during summer monsoon season
●Freeze sensitive
○Damage under 28 degrees Fahrenheit
○Native to semi - tropical India
○Can damage young trees to the point of death
○Older trees are more resilient to the cold and may endure damaged leaves
●NOT a desert landscape tree
●Desert Oasis tree
Ulmus Parvifolia or Chinese Elm
●Name means “elm tree with small leaves”
●Native to China
●Deciduous
●Umbrella - shaped canopy
●Ideal city tree with dense shade and single trunk
●Moderate amounts of water required
●Well - adapted to the hot desert climate in Arizona
●Moderate to fast growers
○Can grow up to 40 feet tall
●Large shade tree
●In late Autumn, after Thanksgiving, leaves turn yellowish - red
○Brief display of Fall color
○Bright green in the spring
○Darker green in the summer
●Puzzle piece bark
●Green, gray, brown, and orange pieces on trunks
●Pruning care includes removing broken or crossing branches in late winter when
deciduous
●Residential backyard, civic space, park, etc.
