Deep and extensive roots

Many deserts and steppes have residual water from past rainfalls deep underground (at depths of 20 to 100 metres). Some desert plants have deep tap roots to access this water. Some varieties can sustain green leaves all year round as a result of this root mechanism. The umbrella thorn acacia has developed a different mechanism. It speculates on minimal quantities of moisture which can be found everywhere in the ground and has an incredibly extensive root system to collect it. Some of the roots can even go down to depths of over 30 metres.