Actually not a moss at all, peat moss is the decomposed materials found in sphagnum bogs. There are several reasons to use peat moss. It is an excellent source of humus and a wonderful soil conditioner. It helps to retain soil moisture and slowly releases nutrients into the soil. As mulch, it also improves aeration and lowers soil pH.
Peat moss can break down clay soils by aerating them, or it can bind sandy soils to decrease the leaching of soil nutrients. It is the main ingredient in many commercial potting mixes and is often used in combination with compost and other organic materials in homemade growing mediums.
Retention of Nutrients
Although peat moss contains very few nutrients naturally, it retains added soil nutrients and releases them slowly as needed. Compost or other nutrient-rich organic materials will need to be added regularly for the slow dispersal by the peat moss.
Peat moss acts like a sponge, soaking up moisture and releasing it slowly, as the soil needs it, keeping plants moist. It has the capacity to retain twenty times its weight in moisture.
With heavy clay soils, peat moss aerates the soil to break it down, allowing plants to establish better root systems. It can also be used to aerate compost piles, and it works as an innoculant to increase the speed of the composting process. In addition, it works well as mulch for new seed beds, retaining moisture while allowing good air flow.
Lower Soil pH
Peat moss is acidic, with an average pH of about 4.5, so it works well to lower the soil pH for plants that like a slightly higher acidity. It can be added to compost piles, which are generally slightly alkaline, dug directly into the garden or used as mulch to achieve this result.