They form an open canopy and, except after rains when annuals may cover the desert floor, the ground between shrubs is bare of vegetative growth. Especially along intermittent streams or under dunes, underground water may be readily available. Mesquite is a good example here in North America. One of the world's most unusual phreatophyes is Welwitschia mirabilis of the Namib. Succulents store water accumulated during rains for use during the intervening dry spells.
Many plant families have members that evolved succulence.
Most succulents do not tolerate freezing temperatures so they are essentially limited to the hot deserts. Another growthform adapted to desert conditions is the ephemeral . 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 undergound tissues and also remain dormant most of the year.