Shredded pine bark lasts as long as two years, depending on the shredding size. Some bark products are shredded finely so that they can decompose faster into the soil -- these barks do not last a full two years but add critical nutrients quickly into the soil. Thickly shredded pine bark works well under perennial plants, such as shrubs, as they decay slowly and resist matting into a barrier on the ground. Because pine bark is an appealing mulch choice, you may want to spread this organic material across much of your garden.
Pine straw is simply dried pine needles. Resembling a forest floor, straw is easily spread across a large garden -- the thin material glides over the soil surface. Typically providing a yellow to orange hue, this mulch contrasts with green foliage to highlight your favorite plants. Spread pine straw under annuals especially; straw decays quickly as annuals only have one year to complete their life cycle. With the lack of viable cellulose in the straw's internal structure, termites look for other food sources rather than populating your garden.
If you spread shredded pine bark too thickly across your garden, you effectively create a barrier to moisture infiltration, especially if the mulch is finely cut. For example, a 6-inch-thick shredded pine bark layer stops water from entering the soil or evaporating properly. Your plants suffer from poor moisture supplies and may die back. Because pine bark may attract pests, it should not be spread close to your home to avoid infestations. Any steep hills around your home do not provide a proper surface for pine bark as well -- it may simply fall away with wind or water erosion.
If you do not water your plants periodically, along with the surrounding mulch, your pine straw quickly dries and becomes a fire hazard. Do not spread pine straw close to any structures and consistently water it to maintain a damp texture. Another pine straw disadvantage is weed seed possibilities. Straw easily holds weeds seeds when sold in bulk; observe your garden for any new weeds and remove them promptly. Heavy rain or irrigation flows may also displace pine straw. To avoid mulch loss, you can apply a wire mesh cover to the ground to keep the straw in place.