Both products are used as soil amendments to improve soil structure by lightening the soil and holding moisture; neither adds nutrients to the soil.

Coir

Peat moss is harvested from peat bogs which are areas of decomposed sphagnum moss in swamps and marshes. Wetland ecologists consider peat moss a non-sustainable material because its harvesting rate is greater than its replenishing rate. Plus, it is harvested from delicate endangered habitats.

Coconut fiber (Coir) is a byproduct of coconut processing; therefore it is always available and sustainable. Coir is made from fibrous coconut husks which are water processed, ground up or decomposed, then made into Coir bricks. Most COIR comes from India, or Sri Lanka.

Differences: pH and water absorption

Product pH – Peat moss is acidic with a pH of 3.3 to 4.0. Therefore, it is used in potting soils for acid loving plants, or it’s used to acidify garden soils with high alkalinity.  A neutral pH is more desirable in most planting situations, so lime is added to peat moss to bring its pH closer to neutral.  Most commercially made peat-moss based potting mixes have added lime. In contrast, Coir has a pH range of 5.2 to 6.6, which makes it more suitable for a wider range of plants.

Water absorption –While proponents of Coir state its water retention is equal to peat moss; peat moss typically retains much more water than Coir.  Peat moss holds 10 to 20 times its dry weight in water, while Coir holds 8 to 9 times its dry weight in water.  Coir does saturate faster than peat moss, thereby using less water to “activate”.  To be fair, Coir comes in various textures and coarseness, which may increase its overall water-holding abilities, but they are not equal.

When given a choice, consider Coir for its closer to neutral pH and its environmental sustainability.