Leaf phenology in a population of the climbing fern Lygodium venustum was observed during a 31-month period in Veracruz, Mexico. The study site is located 100–200 m from the Gulf coast in the understory of a semideciduous lowland forest dominated by trees of Enterolobium and Ficus. Four leaf parameters: leaf growth of main and secondary axes, number of living leaves, leaf production and leaf mortality were scored monthly and correlated with two climatic factors: monthly mean temperature and precipitation. Sixty percent of the 37 individuals were supported on lianas, dead wood or shrubs. Smaller, unsupported plants with a height of less than 2.5 m had a mean number of 1.9 ± 0.27 leaves and produced 3.7 ± 0.52 leaves per year and did not become fertile. Over 50 % of the leaves died within the first 3 months, whereas over 10% lived for 12 to 30 months, resulting in a mean leaf life span of 5.6 ± 0.7 months. All leaf parameters were seasonal with the exception of the growth of the main axes. During the rainy season, leaf growth of secondary axes and leaf mortality increased approximately threefold and leaf production rose twofold. Correlations between climatic factors and leaf parameters were strongest within a time lag of one month. The strongest correlation was found between precipitation and the growth of secondary axes, indicating that water is the limiting factor. One to five dormant buds developed on 17.7% of the leaves contributing to 40.3% of the total leaf growth. The potentially long life span of the climbing leaves and the outgrowing dormant buds make this species a successful pioneer in disturbed vegetation and a competitive weed in Mexican vanilla plantations.