- Shrubs are the
dominant growth form of deserts.
- They may be evergreen or deciduous;
have small leaves (ex. creosote bush: 1,
- have spines or thorns (ex. desert sage:
(ex. Ocotillo: 1)
- aromatic oils (a form of defense) (ex. creosote bush).
- shallow but extensive root systems procure rainwater from well beyond the canopy
of the shrub whenever it does rain.
These are the true xerophytes adapted
to tolerate extreme drought. They form an open canopy and, except after rains
when annuals may cover the desert floor, the ground between shrubs is bare of
Water is not entirely lacking in the desert environment and
several other growth forms represent strategies to reach water or to store water:
- Succulents store water
accumulated during rains for use during the intervening dry spells.
- Saguaro cactus (1,
- Barrel cactus (1)
ephemeral plants (ex: 1,
2). This is an especially short-lived annual
plant that completes
its life cycle in two-three weeks. The seeds are encased in a waterproof
coating that prevents desiccation for years if necessary. These plants
essentially avoid drought by occurring as seeds most of the time.
- Perennial forbs with
underground bulbs store nutrients and water in underground tissues and also
remain dormant most of the year. They can sprout rapidly after sufficient
rains and replenish their underground stores.