Plant development consists in various synchronised processes.In particular, the process of leaf apperance or*phyllochron*, characterised by the time of appearance of each leaf, is often studied as an easily observed indicator. In this talk, I will present a statistical model for phyllochron with independent time intervals between leaves, when the times of leaf appearance are interval censored. . First, assuming Gaussian distribution of time intervals, we have implemented a Monte Carlo EM algorithm, which makes use of a generator from the truncated multivariate normal distribution. A more general parametrisation can be considered using the framework of semi-Markov models ; then the forward-backward algorithm, originally developed for hidden semi-Markov models, can be adapted to the interval censoring context.