Do I need a landscape architect?

Many larger nurseries will assist and advise on what to plant, where
to plant, and how to maintain the grounds.

Thanks for your comment tispiegel.... Perhaps I should have been more
verbose in my question. I just built a new house on a 4 acre property
that I want to develop. I've got some drainage issues, want to plant
of course, would like to put in a sprinkler system and finish by
puting in a driveway and walkways. As you note for planting my nursery
will help as will other professionals for various projects. However I
am concerned about coordinating the work, making sure that all local
regs are followed etc. Use of a landscape architect might help but I'm
not certain of this and don't want to add the 15=20% cost overhead
unless there is true value to be gained.

Hi sanesmith,

Thank you for a more detailed explanation. 

Hopefully a researcher will be able to come up with an answer for you.  

Best regards,
tlspiegel