Sod is grass that has formed a living carpet Many grasses grow by forming an intricate root system which travels outward and resurfaces, forming new blades of grass.
This behavior can be undesirable, for instance with bamboos that over take an area, or for gardeners who would like the grass to stay out of their garden.
But for sod farmers, and those who purchase sod, this property of "running" gives makes sod grasses possible.
Thus, a sod farmer can sow an area of grass and the individual plants spread out and intertwine with their neighbors.
After a couple seasons, the layer of dirt below the lawn is a solid tangle of roots.
Sod refers to both the visible grass and also the zone of roots extending a couple inches into the soil.
Although grass roots can run deeper, the first two inches of dirt are filled with this complex tangle which forms a mat.
This mat can be scraped up from the ground by sod farmers who grow fields of turf for relocation to customer's yards.
It takes a couple years for a newly seeded area to become established enough to be pulled up in sheets.
Thus people who purchase sod are paying for the use of that land on a sod farm for several years, along with water and labor over that time.
A Sod grass lawn is therefore significantly more expensive than a sown lawn.
Because of this cost, sod grass is most often used for special events and grand openings where a perfect lawn is needed quickly.
It takes only two weeks for transported sod to establish itself well enough to be walked upon.
A seeded lawn could take any number of months to establish itself well enough, although a full season is best.
Sod grasses should be bought as locally as possible, as sod laid in a climate similar to where it was grown will do best.
Lacking a local sod source, choosing the correct warm or cold season variety will help ensure the sod takes to its new environment.