Peat moss makes heavy soil fluffy, helps sandy soil hold water and provides a gentle bed for new seedlings. Although it is nutrient-poor, it is highly acidic and tempers alkaline soil. If you want to grow acid-loving plants, peat moss is a welcome addition to your garden and will improve your soil for years to come.
Often called peat moss, peat is not a moss itself but consists of compressed sphagnum moss (Sphagnum spp.). Sphagnum moss grows in cool climates and extremely wet soils. Peat forms as sphagnum moss grows on the surface of old, slowly decomposing moss layers. These layers form over dozens and even hundreds of years -- according to Washington State University, a bog forms 1/4 inch of peat per year. Companies mine blocks of peat from these peat bogs for use in gardens and nurseries.
Peat is more acidic than most soil amendments and has a low pH level of roughly 4.0. While most garden plants prefer more neutral pH levels ranging from 6.0 to 7.0, acid-loving plants prefer soil pH levels as low as 4.5. Without these low pH levels, acid-loving plants are unable to take up iron and other soil nutrients, causing chlorosis, decreased bloom and other problems. For example, potato scab may affect potatoes grown in a pH higher than 5.3.
To decrease soil pH levels for acid-loving plants, work 1 to 2 cubic feet of peat per plant into the soil. For new plantings, the Iowa State University Extension suggests using 50 per cent peat and 50 per cent soil in the planting hole. Test your soil pH level before and after adding peat to ensure the best acidity level. While the effects may last six years or more, eventually the peat decomposes and will need replenishment.
Common acid-loving plants include rhododendrons, hydrangeas and blueberries. These plants prefer pH levels between 4.5 and 5.2. Evergreens thrive with slightly acidic conditions in the 6.0 range, as do many lawn grasses. American holly (Ilex opaca), heathers (Calluna vulgaris) and bayberry shrubs (Myrica pensylvanica) also prefer acidic soils. Carnivorous plants, such as pitcher plants and sundews, require acidic soil, being native to acidic peat bogs.