We sampled vegetation and soils of, and classified mid-seral, even-aged, fire-origin, upland Picea mariana ecosystems in the boreal white & black spruce and sub-boreal spruce zones of British Columbia, Canada. We applied multivariate and tabular methods to analyse and synthesize the data from 121 plots according to the methods of biogeoclimatic ecosystem classification. We delineated seven basic vegetation units and described their vegetation and environmental features. However, the delineated units could not be related to neither of the taxonomies proposed for the North American boreal forest communities. Although species-poor, the understorey vegetation in the sampled ecosystems provided for a sufficient floristic differentiation, which matched well the major edaphic differences between the units. The classification of mid-seral boreal ecosystems may be more useful that based on old-growth stands that are infrequent or lacking in the landscape due to wildfires.