The underground phase: a special challenge in studies of terrestrial orchid populations

Orchid seeds are minute and the first seedling stages of terrestrial species are underground, so there is little knowledge about the biology of the early life history and the size of seed/seedling populations relative to the number of plants that eventually emerge above ground. A recently developed field sowing technique makes it possible to explore a variety of topics such as the length of time that seeds spend as part of the soil seed bank, the phenology of seed germination, substrate requirements for germination, dependence of germination on fungal availability, substrate requirements and growth rate of seedlings, seedling phenology and development, and seedling‐fungus specificity patterns in the soil. Several of these applications are relevant for conservation issues. Studies of Goodyera pubescens, Corallorhiza odontorhiza and Liparis lilifolia show considerable variation in germination strategies, patterns of seedling development and establishment, substrate requirements, and levels of specificity with the fungi.