Fig. 3. Frequency distribution of categories for reasons given for planting by natural and social factors over the entire gradient. R1: regional character; R2: resistance-adaptation; R3: esthetics; R4: donation-gift; R5: professional advice; R6: use; R7: propagation; R8: easy maintenance; R9: symbolism; R10: imitation; R11: remembrance; R12: specific flowering; R13: previous presence in garden; R14: past experimentation; R15: change; R16: usefulness for another plant; R17: other.