The effects of lifting date and increasing drought stress on root electrolyte leakage (REL) and moisture content of seedlings of Carpinus betulus, Fagus sylvatica and Picea abies were assessed to obtain threshold values for predicting plant quality. The relationships of REL and moisture content to survival were determined. Lifting date influenced REL and moisture content; a higher shoot moisture content (SMC) was found in October and March/April, while highest REL and moisture percentage of the roots was found in October. Furthermore, interpreting values of REL and moisture content without knowledge of the 'hardened' or 'dehardened' state of the plant could lead to wrongly classifying plant quality. Seasonal observations of bud dormancy showed that bud dormancy is insufficient for indicating the 'hardened' and thus more stress supporting state of the plant. Seasonal changes of nonstructural carbohydrates indicated that for the studied species the presence of raffinose and/or stachyose in bud or stem tissue were good indicators for 'hardened plants' and could help to interpret REL values and moisture content levels with respect to plant quality assessment.