Palm trees are native to warm areas, such as moist areas in
deserts and many
tropical areas. Although palm trees grow quite large they are actually more related to
grass,
onions, and
agave than they are to most other trees. This is because they are
monocots, as opposed to
hardwoods (
dicots) or
conifers (
gymnosperms). The palms that are the most used in landscapes are California and
Mexican fan palms (genus
Washintonia) and the large-leaved
Canary Island Date Palm (genus
Phoenix).
Palm trees don't do well in cold weather, so they are mainly restricted to areas like
California and
Florida in the US, and other equally warm areas around the world. They have come to be a symbol of sorts for
Los Angeles, as they are very commonly planted there. They are not actually native to the
Los Angeles Area.
Palm trees can be interesting and valuable additions to a landscape, however like any other tree they do have problems. As noted by SilverSurfer, they are a habitat for such animals as rats, roaches, and pigeons. You can keep rats out by putting a metal ring around the trunk; unlike most trees this will not kill the tree as it grows. Also, if dead leaves are not trimmed off, they can be a big fire danger. Palm trees are easily transplanted and can be bought full-size, if you have a lot of money.