The von Post scale is described in Table 1. Dark, more decomposed Sphagnum peat still can be fibrous. Peat producers are constantly improving peat harvesting equipment so that the fibrous nature of Sphagnum peat is destroyed as little as possible during harvesting. The darker H 4 on the von Post decomposition scale level peat has high cation exchange and buffer capacities. Therefore, this type of peat is ideal for incorporation in container media because disease suppressive effects in nursery media typically are supplied by either bark or other composts.
Sphagnum peat is deficient in macronutrients as well as micronutrients.
Lime, starter fertilizer, and micronutrients all must be added to peat mixes unless composts containing such nutrients are added to the mix as well. Two general types of pine barks are available to Ohio growers - red pine bark from Michigan and a mixture of five species from the Carolinas through the southeastern states to Texas. All are high in lignin and wax contents, which resist decomposition. This makes pine bark an excellent peat substitute. Growers need to select sources of pine bark that are low in wood content and of consistent quality.