library(ggforce)
library(ggplot2)

leaf <- data.frame(
  x = c(1.6, 1.5, 1.8, 1.5, 1.6, 1.3),
  y = c(2, 2, 1.5, 1, 1, 1.5)
)

ggplot(leaf, aes(x, y)) +
  geom_polygon(fill = NA, colour = 'grey') +
  geom_point(colour = 'red') +
  geom_bspline_closed(alpha = 0.7) +
  coord_fixed()