The difference between drought tolerant and drought resistant plants?

Define drought tolerant.  What is a drought resistant plant? Here is the difference between drought tolerant (true desert plant) and drought resistant (originated in semi-arid places).

A flower or plant that has naturally evolved to survive periods of drought with little water and has the ability to tolerate substantial dehydration of their tissues and organs is drought tolerant.  Xerophytes are the BEST drought tolerant plants, shrubs, trees, and cacti.

cactus plants use little water are heat tolerant
Drought tolerant Saguaro Cactus and Prickly Pear Cactus

Cacti and many plants survive on little water and make Xeriscape not only essential but pleasing to the eye. Derived from the Greek word “xeros”, meaning “dry” and combined with landscape, xeriscape means gardening with less than average water.

drought resistant landscape yard
flowering, hairy cactus with drought tolerant agave plants

Many xerophyte plants have specialized tissues for storing water, as in the stems of cacti and the leaves of succulents. Others have thin, narrow leaves, or even spines, for minimizing water loss.  Xerophyte leaves often have abundant stomata to maximize gas exchange during periods in which water is available, and the stomata are recessed in depressions, which are covered with fine hairs to help trap moisture in the air.

drought resistant tolerant bushes in yard design
xeriscape yard with XEROMORPHIC plants like cactus, yucca, ocotillo

Drought tolerant plants have adapted by making use of either C4 Carbon Fixation or CAM (crassulacean acid metabolism) a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions.

xerophyte plants best drought resistant
A drought tolerant Joshua Tree and Yucca Cactus in this photo

In a plant using full CAM, the stomata, in the leaves, remain shut during the day to reduce the loss of water as vapor, but open at night to collect carbon dioxide (CO2). The CO2 is stored and then used during photosynthesis, which is the process of capturing the suns energy.

what is drought tolerant and resistant plants
Saguaro cactus and Palo Verde Tree are well – adapted drought tolerant plants.

CAM is particularly good for arid conditions because CO2 can be absorbed at night, allowing the pores on the leaves to stay closed during the day and thus reducing water loss. A easy way to explain it is drought tolerant plants can slow down metabolism.

Blue agave cactus plant with spike leaves in desert
Lovely Agave titanota BLUE variety

High elasticity of the cytoplasm and the capacity to withstand compression of the cells during dehydration are characteristic of drought-tolerant plants. What is cytoplasm? An easy definition of cytoplasm is a gel-like casing, covering – containing all the contents of the cell’s organisms, except the nucleus. Most metabolic (chemical reactions) pathways occur in the cytoplasm.

ocotillo tall cactus for drought tolerant yard arizona
Ocotillo Cactus plant in the desert

Not to be confused with drought-tolerant plants, Drought Resistant plants are not true desert plants. Many have originated in semi-arid regions, the area around the Mediterranean, Latin America and sub-Sahara.

Here are pictures of drought resistant plants that are not native desert plants.

color ideas for your desert low water, garden
colors of flowering lantana drought resistant plants next to oleander bushes

Lantana

drought tolerant and heat resistant flowering plants of the desert
The New Gold Lantana along with Trailing Purple Lantana plants
drought tolerant flowering lantana plants
White, Red (Texas) and Gold Lantana drought resistant desert plants

Lantana, in the verbena family, is a highly attractive drought resistant flowering plant that originated in tropical regions of Africa and the Americas.

drought tolerant and heat resistant purple lavender plant
lavender shrub is drought resistant

Lavender

top best drought tolerant flowering plants
young lavender drought resistant plant

This plant has it all: Drought resistant, it looks great, it smells wonderful, and it’s as tough as nails (as long as it’s not too wet).  Lavender is in the mint family and originated in the Old World around the Canary Islands, Africa, India, and Asia.

best drought tolerant heat resistant desert plants
Yarrow, yellow flowering drought resistant plants

Yarrow

Not only does yarrow tolerate heat and drought like a champion, but this easy-growing perennial is also a great cut flower.  Yarrow, Achillea millefolium, originated in regions of Asia and Europe.

best drought tolerant heat resistant desert plants
Yarrow (Achillea millefolium) drought resistant plants

There is a difference between drought resistant and drought tolerant plants. Knowing the difference can save you considerable heartache.

Interesting Saguaro Cactus Facts

One of Arizona’s most majestic, lovable desert cactus plants is the Saguaro, Carnegiea gigantea. Being aware of the saguaro’s history and incredible internal design, it is an honor to walk close to the Giant Saguaro that is over 150 years old and standing tall.

Sonoran Desert cactus tall
Giant Saguaro Cactus of Arizona

These desert cacti are large, tree-like columnar cacti that develop branches (or arms) as they age.

Saguaro Cactus can not tolerate freezing temperatures in the winter and this is what limits their range.

Saguaro National Park
Saguaro Cactus

Saguaro FACTS:  Saguaros are a very slow growing cactus.  A 10 year old plant might only be 2 inches tall.

How tall can a Saguaro Cactus grow?  It can grow 40 to 60 feet tall.

Arizona Saguaro Giant Cactus
Saguaro Cactus on Mica Mountain
60 foot Saguaro Cactus plant
A Tall Saguaro Cactus

Below are Saguaro cacti at the bottom of Mica Mountain in Saguaro National Park.

Mica Mountain Saguaro National Park

Saguaro cactus roots are only 4-6 inches deep and travel out as far from the plant as it is tall. There is one deep tap root that extends down into the ground.

A Saguaro Cactus can gather enough water through its remarkable root system, during a significant rain, to last a year!

holes in big cactus
Holes in Saguaro Cactus for birds nest

Why are there holes in the Saguaro Cactus?  The gilded flicker and Gila woodpecker excavate nest cavities inside the saguaro’s pulpy flesh.

Birds nesting in the Arizona Saguaro Cactus

Cactus Wrens are common birds that live in the holes (nests) of the Saguaro Cactus.

red fruit of cactus
Saguaro Cactus Flowers bloom, then turn to fruit

When a saguaro reaches 35 years of age it begins to produce flowers.

white flower on cactus arizona
Saguaro cactus Bloom – Flower

A Saguaro can only be fertilized from a different cactus – cross pollination.  Only a few bloom each night awaiting to be pollinated and close by late morning.

pollinated cactus flower to fruit
red fruit on Saguaro Cactus
dead saguaro cactus ribs
A living and dead Saguaro Cactus.

Because the major part of a desert saguaro cactus is made up of water, an adult plant may weigh 6 tons or more. This tremendous weight is supported by a circular skeleton of inter-connected, woody ribs.

After the saguaro dies its wood ribs can be used to build roofs, fences, and parts of furniture.  The holes that birds nested in are called saguaro boots.

holes in cactus in Arizona
Saguaro Boot used by Native American

Native Americans used saguaro boots as water containers.

200 year old tall saguaro cactus
Saguaro Cactus next to a biker to compare the size

Saguaro branches normally begin to appear when the cactus reaches 50 to 70 years of age.

The average life span of a saguaro is approximately 175 years of age.  Experts have estimated that a Saguaro Cactus with more than 5 arms can be 200 years old.

nurse tree for saguaro cactus
Yellow Palo Verde Tree is a nurse tree

Young saguaro cacti can be very hard to find because they grow under the protection of a “nurse tree”.  The nurse tree releases nitrogen in the soil which the Saguaros and other desert cacti use to grow healthy and strong.

Saguaros sometimes grow in odd shapes or forms. The growing tip of the cactus occasionally produces a fan-like form which is referred to as crested or cristate.

rare arizona cactus
Cristate Saguaro Cactus

These crested saguaro cacti, Carnegia gigantea forma cristata, are rare.  Biologists are not sure why these Saguaros grow this fan-like shape.

Fan like shaped cactus rare
Crested, Cristate, Fan-like Saguaro Cactus from AZ
crested cristate cactus in Tucson Phoenix
rare Saguaro in Tucson

Arizona has strict regulations about the harvesting, collection or destruction of  The Arizona Saguaro Cactus. It is illegal to harm a Saguaro in Arizona. During building or construction, precautions must be taken to move every saguaro that may be affected.