Desert Plant Adaptations

8/6/11
     After moving to the desert southwest and finding it difficult to deal with the blazing hot sun and triple-digit heat, I wondered how the native plants and trees survived here.  After researching, I found that desert plants and trees have devised unique adaptations to survive the intense heat and sun.

tiny leaves - mesquite tree

I noticed that most native trees, bushes and plants have very small, even tiny, leaves.  As I suspected, tiny leaves have limited surface area reducing water requirements.  I also discovered that some plants reduce moisture loss by foregoing traditional leaves.  Cacti spines are actually modified leaf parts with sharp points.  Cacti and other desert plants also reduce water loss through their stomata (pores) by opening them at night when temperatures are cooler.  Another adaptation to reduce moisture loss is a waxy coating found on such plants as creosote and cacti.  When there is an extreme drought, some trees like the palo verde drop their leaves so there is less plant material that needs water.  When rainfall occurs, leaf growth returns.  I have noticed when we have a rainfall, some bushes, like Texas sage, burst into bloom a few days later.

tiny leaves - palo verde tree

To take advantage of any rain that falls, plants such as agave, hesperaloe and yucca use their funnel-like shapes to collect rainwater and direct it to their main stem and roots.  The spines of cacti act as drip tips for the same reason.  I also learned that cacti develop shallow, but wide-ranging root systems to have a better chance of absorbing rainfall.  An example is saguaro roots, which can extend up to 100 feet in all directions.  Also, cacti and other succulents can store water in their roots, stems and fleshy leaves to use during dry spells.

funnel-shaped desert spoon plant

golden barrel cacti spines as drip tips

     One thing particularly noticeable here in the desert southwest is that many trees and plants are not truly green.  Many, like Texas sage, have gray, silver or pale green foliage.  This is a modification that helps reflect sunshine and reduces heat build up on the leaf's surface.

Texas sage gray-green leaves

bush morning glory silver-green leaves

     Other plants, like brittlebush, have fuzzy hairs on their leaves that act as sun reflectors to keep the plant cool.  Some plants, like the jojoba bush, angle their leaves vertically so that surface area exposed to the sun is minimized.

vertical leaves on jojoba bush

vertical leaves on hopseed bush

     Adaptations to reduce moisture loss, harvest rainwater and reduce sun exposure help desert plants thrive.  Since non-native plants do poorly in the intense heat and sun, most homeowners here choose low-maintenance, water-thrifty native adapted plants for the bulk of their landscaping.