the oldest leaf forms the outermost layer of the crownshaft. eventually the lowest palm frond dies back, the outer layer of the crownshaft splits, the leaf unwraps and pulls away from the trunk exposing the new crownshaft surface. in time the old leaf separates at the base and falls away leaving the distinct rings and ridges of the leafbase scars seen on the trunks of many species of palm. these scars usually fade over time and the distance between two successive scars is an approximate indicator of the speed of growth of the palm. in tropical conditions when growing conditions are good, the palm grows faster and the gap between scars is large; conversely when growing conditions are not optimum, plant growth is slow and the gaps are narrower. juveniles and younger palms usually grow faster than adults; this is demonstrated by the larger gaps between scars at the base as compared to the top.