Pine straw is a term used in the southern United States to refer to pine needles. A pine tree will produce pine needles that can be anywhere from 5 to 18 inches in length, the most desirable type of pine straw is referred to as Longleaf pine straw. These needles will fall to the ground and are then harvested for use as a mulch.
Pine straw has been used mainly in the southern US in the past, but has more recently become available in other parts of North America as well. Like regular straw, pine straw is lightweight and porous, so it can be laid thickly as a weed barrier. It is also much slower to biodegrade, and has a better nutrient value.
Its major liabilities include expense (in areas far from where it is harvested), and the strong acidity of the needles as they break down (though this is actually an asset when growing ericaceous plants and other acid-lovers). Pine straw can also make cleanup difficult, as fallen leaves and other debris tend to get stuck in a pine straw mulch, making it difficult to either rake or blow off debris without removing the mulch itself in the process.