Because Ilan is at a low altitude and has many springs, the roots find it easy to quench their thirst and the trees 'crowns grow lush and full. Full of springs and developed by man relatively late, the areas where the mountains meet the plain have most of the remaining banyans.
宜蘭因為地勢低，容易出現湧泉，樹根汲水輕而易舉，樹冠也就猛長亂竄，尤其山坡與平地交接處的湧泉帶，開發較晚，僅剩的大榕樹就多生長在這一地段。