Water content (WC), water potential (ψt) and pressure-volume derived osmotic potentials (π) measured in foliage from saplings of Nothofagus solandri var. cliffortioides (mountain beech) at Craigieburn Forest Park timberline, 1370 m, New Zealand and Pinus cembra at Stillberg, 2100 m, Switzerland, did not change critically through the winter, except in mountain beech foliage frost damaged in early autumn. ψt of both species remained about -1.3 MPa, and WC fell no more than 20% below saturation. Sun warming of mountain beech stems allowed some water transport in mid-winter and ψt of mountain beech was higher at midday than in the evening. Cuticular conductance, measured on mountain beech at ψt>-3.0 MPa, increased steadily through the winter but water loss from this source was small. Strong seasonal suppression of stomatal conductance was related to low air temperatures and reduced water uptake at low soil temperatures. Post-winter photosynthetic assimilation and stomatal conductance were below pre-winter levels. The absence of snow protection for mountain beech did not cause winter ψt to fall more than in P. cembra under snow. Mountain beech does not reach the true upper limit of tree growth in New Zealand as plantings of hardy northern hemisphere pines survive to 1750 m, an altitude where growing season climate and snow protection are more equivalent to Europe.