Since Los Angeles is in a semi-arid environment, remnant or feral vegetation in noncultivated spaces of the urban environment tends to be weedy
and scrubby and trees rarely regenerate, except where there
is water. In irrigated but poorly maintained areas, such as in
freeway interchanges, one might find a mix of eucalyptus, Schinus terebinthifolius, Ailanthus altissima, and other opportunistic
species. In non-irrigated areas, there are low-growing grasses and
Mediterranean-region invasive plants