We did this once before and laag gave us the definitive answer, anyone remember it and where to to find it.

If you use subs, you have to remember that you are taking on the responsibility of coordinating all of them. Sometimes that means that you can have serious conflicts if you do not know how to manage a construction job.

example:You have a pool guy com in and install a pool. You hire a hardscaper to build a patio only to find that you now need to add or remove a step from your brand new deck in order to drain the patio right. Then you hire the irrigation guy who now needs the patio opened up because there is no way to run his piping around it. Same with the lighting guy. .....

Some projects are not rocket science and some homeowners are pretty sharp, so you may be able to manage subs ... but be prepared to grab your own throat when something is screwed up.
You don't have to hire a company that can do it all, but it is a pretty good idea to hire one that can at least bring in subs that (s)he has worked with often and coordinate them for you.

Here are a couple of classic rants.

http://forums.gardenweb.com/forums/load/prof/msg101320366661.html

http://forums.gardenweb.com/forums/load/prof/msg1012563615949.html

Juggling trades is difficult but in your situation, I don't think there's any reason to have more than two different contractors.

I would hire one contractor to tackle the irrigation and one contractor to do the other tasks. All the other tasks should be pretty standard work for a medium-sized landscaping company.

Make a plan, meet with each sub and put together a time line. This will hopefully avoid unnecessary modifications and the resulting expense or loss of time. The money you save in hiring your own subs may not be worth the headaches and often results in finger pointing when something goes wrong. As a rule of thumb, the larger the job the higher the chances of something going wrong. I tell my clients that the general contractor is the puppet master. He should see the larger picture and know the order of things. Also, it does protect you if you one person who holds the liability. Ask for a contract and READ it!! Good luck

I do project management for my landscape design clients, and my contractors of choice are pretty well-rounded. On a job like yours I'd have two contractors involved only because in VA, most landscape companies don't also do irrigation.

Generally, the reason I see people split a project up between multiple companies is that they think it's the cheapest way of doing it. Being your own GC is tough. Being your own GC with multiple crews who have all the problems that go along with being on the lower end of the industry (overbooked, understaffed, never know when they're showing up, job drags on, poor quality work, stuff put in the wrong place)is miserable.

If you hire one vendor, maybe they do it all in house, or maybe they sub it. Who cares? As long as they're a quality contractor with happy past clients and quality installs as references, there's no problem. Any markup they put on the sub is paying them for their time to ensure that the project is done correctly.

You may want to make sure that the mindset behind phrases like "one throat to choke" doesn't show up in your meetings with contractors. I know that if I heard that expression come up in a meeting I'd be headed out the door.

Marcinde has given you great advice, and I hope you particularly note how poor choice of language when dealing with contractors/designers can be self defeating. I'd be out the door too.

If a contractor is worried about having their neck on the line, then I don't want them. I work in an industry where multiple vendors are often supporting the client and a big component of our value proposition is consolidating the work and offerting them one source of accountability ("one throat to choke") should they have any issues. No need for them to worry about figuring out who is really at fault. If there's a problem and they feel the need to go choke someone's throat, it will be ours; we'll take full accountability for the work. If you can put yourselves in the shoes of the customer; can empathize with their desire not to deal with finger pointing; and you're willing to suffer the consequences should something go wrong, then it's the perfect language. There are plenty of vendors though who are not so comfortable stepping up and taking full responsibility or who can't understand their customers frustration from hearing all the excuses. And that's great for us.

The thing that is left out of this whole story that you don't realize unless you are around it all of the time, is that subs are responsive to those whom they have an established relationship with (those that have and will continue to feed them work). Coordinating multiple subs is more often than not, all about timing - this needs to be done before that can proceed, ...etc,...
If you do not get that rough grade, you don't get your irrigation piped installed, if you don't have the irrigation running properly, you don't get your sod, ..

Believe it or not, if you schedule them to be in on Thursday morning and they get a call from someone that they continually sub for, they ain't coming.

You can't overlook that some subs don't like other subs and can be less accommodating for them. When you hire "one throat", they usually have a core of subs who know the details of how the others do things and are programmed to set the others up without a lot of discussion. Familiarity makes things flow easily. When subs have not worked with each other, expectations and assumptions that somethings will be done a certain way may not be accurate - not done poorly, just different than expected causing the others to have to adjust.

Nope. Gonna disagree with you there, and this is coming from someone who has been in the trades for years: language that references, threatens, or implies physical violence is never appropriate in business. You may see it as a shorthand way of expressing a philosophy; I see it as a potential flag that you're a jerk who hits his kids and honks at old ladies in crosswalks. You may be an awesome guy, but that one turn of phrase means I am not comfortable working with you because you are potentially a volatile, irrational personality and not worth the money. Again, is this accurate? Maybe not, but life is too short to work with folks who aren't awesome.

That's not to say that I (or others like me) don't take responsibility for the success of the project. That's why I think having a single point of contact, be it a project manager or a GC, is the way to go. Yes, there are always crappy GCs who will try to wriggle out of their responsibilities. Unfortunately, that's where you as the homeowner have to do your research to make sure they aren't the ones you hire.

That last paragraph laag hit the nail on the head.
Been there, done that. Both ways. I was a Landscape Contractor for over thirty years.....and did irrigation!
Mike...retired.