There are no specific recommendations as to how many crops you can grow in forest-farming operations. However, several factors need to be considered when deciding the number of crops you want to grow:
1) Growth and cultivation methods required of the species of interest.
2) Soil conditions as they pertain to physical and chemical characteristics (e.g., low soil pH).
3) Species susceptibility to pests and diseases. Note that some species diversity is promoted in forest farming.
Crop diversification is considered as insurance against the failure of any crop. Species and temporal diversity are characteristics of natural forest ecosystems, which forest farms ideally should seek to emulate. For example, in forest farming, if growing mushrooms, maple products, and ginseng, diversification makes good sense from a production standpoint; maple is tapped yearly, mushrooms yield a harvest for several years, while ginseng will take eight years to mature. In this case, the maples also provide shade for both other crops and additional calcium (in fallen leaves) needed by the ginseng.