Key message Alternative growth forms of C. madagascariensis (liana, shrub) did not differ with respect to biomass allocation to aerial organs or leaf area ratio contrasting to previous liana vs. tree/shrub comparisons. Compared to trees, lianas allocate less biomass to support functions, investing instead in stem elongation, leaf area expansion and reproduction, making them more efficient at obtaining resources in crowded stands. We hypothesized that growth form plasticity, accompanied by shifts in biomass allocation to different aboveground organs, can be advantageous to invasive liana species, enabling them to invade both crowded and open stands. We tested this hypothesis by destructively collecting the above-ground parts of individuals of a vine species invading Brazilian northeastern ecosystems. Using allometric models relating height, above-ground biomass (AGB), biomass fractions of above-ground organs and leaf area ratio (LAR) to diameter, as well as wood density (WD) and specific leaf area (SLA) measurements, we verified size, allocation and investment differences between supported and self-supporting plants. We found that a quadratic model described organ fraction vs. stem diameter allometry better than power functions employed previously. Support use allowed plants to reach greater height and AGB, but didn't induce plasticity in fractional biomass allocation and investments (SLA, WD) or in LAR. This demonstrated that support use is not always accompanied by changes in allocation patterns as shown previously. Higher AGB and height in support-using plants allow better leaf display, resource supply to leaves and dispersal. Previous studies with the same species showed that juveniles modify biomass allocation under light limitation. These findings suggests that biomass allocation plasticity due to support use depends on how much light is a limiting factor. Developmental plasticity under different limiting factors may contribute to invasion success.