grass seed mixtures could vary greatly. You need to check for type of seed and its percentage of the mix.

Typically a "contractors" mix will have annual grasses in them for quick germination in addition to perennial rye.
Annual grass will last the year, but then the lawn will be bare, once the temps. drop.

A better seed mix will have varying fescues, and some perennial rye for quick establishment.

Some will also have a portion of kentucky bluegrass.

For shade areas your types of grass will change to red fescues.

So when it comes to seed, don't always grab the cheapest.

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Contractors mix is typically used when builders want to get a quick lawn and are not educated or do not care about the long term stability of the turf.

 

What do you consider "regular" grass mix?

 

Pretty much what Bam said. With a contractor's mix the lawn will look good until the house is sold, then turn to crap.

In my area, many of the building contractors just York rake the lawn area, maybe add some horse manure and throw down some cheap seed which is mostly annual rye. The next thing you know it's a weed field.

I buy my seed from a local garden center that has their own blend made up. What grows best really depends on your area.

 

Here's an example of a "contractor's mix" from Scott's:

http://www.homedepot.com/prel80/HDU...ffdfgidgmm.0&CNTTYPE=PROD_META&CNTKEY=Products_2/Garden Center&MID=9876&pos=n18

Oppossed to some of the Pure Premium blends like:

http://www.scotts.com/index.cfm?fus...Id=&dsvs=FA175E92-27D8-44C6-B249-941D6F4A6477,x,x&CFID=1067326&CFTOKEN=98335437

 

Contractor's mix in my experience is cheap with lots of weed seed in it. Never grows well, I don't buy it.

 

contractors mix = johnson grass seed

 

a contractors mix will have a mix of creeping fescues, for shade, tall fescue for heat, and rye, for quick establishment. these are all great for their certain situations, but not for unintended use, which many contractors use them for. also, the PLS (pure live seed) is much lower than that of a quality seed you would get from a distributor.