The host-dependent support habit of lianas is generally interpreted as a strategy designedto reduce resource investment in mechanical tissues; this allows preferential allocation to leafand stem extension thereby enhancing productivity and competitive abilities. However thishypothesis has not been rigorously tested.?We examined the aboveground allometries regarding biomass allocation (leaf mass andcurrent-year stem mass (approximated as biomass allocated to extension growth) vs totalaboveground mass) and long-term apparent growth patterns (height and aboveground massvs age i.e. numbers of growth rings) for nine deciduous liana species in Japan.?Lianas had on average three- and five-fold greater leaf and current-year stem massrespectively than trees for a given aboveground mass whereas the time course to reach theforest canopy was comparable and biomass accumulation during that period was only one-tenth that of co-occurring canopy trees. The balance between the lengths of yearly stemextension and existing older stems indicated that lianas lost c. 75% of stem length duringgrowth to the canopy which is probably a consequence of the host-dependent growth.?Our observations suggest that although lianas rely on hosts mechanically allowing forshort-term vigorous growth this habit requires a large cost and could limit plant growth overprotracted periods.