What is it?
Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of this material.
The term sod may be used to mean turf grown and cut specifically for the establishment of lawns. However, in British English such material is more usually known as turf, and the word "sod" is limited mainly to agricultural senses (for example for turf when plowed), or avoided altogether, due to the alternative offensive meaning of the word "sod".
Sod (or turf) for lawns is grown on specialist farms. It is usually grown locally to avoid long transport and drying out and heat buildup of the product. It is sold to landscapers, home builders or home owners who use it to establish a lawn quickly and avoid soil erosion. The farms that produce this grass may have many varieties of grass grown in one location to best suit the consumer's use and preference of appearance. It is usually harvested 10 to 18 months after planting, depending on the growing climate. On the farm it undergoes fertilization, frequent watering, frequent mowing and subsequent vacuuming to remove the clippings. It is harvested using specialized equipment, precision cut to standardized sizes. Sod is typically harvested in small square slabs, rolled rectangles, or large 4-foot wide rolls. Some large sod farms may export internationally. Because of the product's short life after harvest, the sod may be washed clean of the soil down to the bare roots (or sprigs) which makes shipping lighter and cheaper. Sod can be used to repair a small area of lawn that has died.
Many grasses can not be grown and cut for sod.
Sod is of course the easiest lawn to establish, and the quickest. Just roll out those brown cylinders, exposing their lush green inner cores, and voila! an instant lawn. Well, not quite. Even sod needs to be pampered for the first few weeks. This method does have several advantages, though, over all the competitors: it gives a finished look immediately, and a finished product within weeks. Furthermore, since there's no bare dirt once the lawn is laid, there is also no place for weeds to get a purchase, so weed problems tend to be minimal.
One of the biggest drawbacks of sod is that many grasses cannot be grown and cut for sod -- they just don't respond well to having their roots sliced and then being rolled up and hauled away on a truck. Of those that will tolerate this treatment, only a few may be available in an particular area. In general, only creeping grasses have been available as sod, because their rhizomes and stolons help them form a dense mat that will hold together under the stresses of cutting and transportation. However, some mixes are now available, including, for instance, mixes of Kentucky bluegrass (a rhizomous grass) with various fescues (mostly bunch grasses), which makes a more shade-tolerant mix than pure Kentucky.
What is the cost of sod?
Different types of sod will have different pricing. The availability of sod grasses is generally dependent on where the lawn is located climate-wise. For the United States, landscapers in the northern states will generally sod a lawn with either Kentucky bluegrass or tall fescue. Kentucky bluegrass has a nice deep green color to it, while tall fescue though not as deep green is excellent for areas that receive medium to heavy traffic since it can resist a lot of abuse. The best, some claim, is a compromise between the two, namely, a grass mixture. Mixtures are also preferred for another reason: disease. "Most [grass] diseases will only strike one type of grass, so the damage will probably be limited. Mixed grass sod is sold containing a percentage of Kentucky bluegrass, tall fescue, and/or ryegrass to fill this need.