Climate change has led to shifts in phenology in many species distributed widely across taxonomic groups. It is, however, unclear how we should interpret these shifts without some sort of a yardstick. We assessed climate change effects on Allagoptera arenaria, a acaulescent palm, using open top chambers (OTCs) and rain gutters in the field to mimic expected temperature and rainfall changes in this area. In a coastal environment (restinga), using open top chambers (OTCs) and rain gutters in the field to mimic expected temperature and rainfall changes in this area, 40 A. arenaria individuals were selected and randomly allocated to four treatments: control (C), 25% rainfall increase (P), 2 °C temperature increase (T), and 2 °C temperature plus 25% rainfall increase (TP). For 2 years, every two weeks, we measured changes in growth and reproduction phenology to assess whether this species altered allocation patterns in response to new environmental conditions. Increases in aboveground biomass were higher in the TP than in the T treatment, which in turn had more reproductive cycles throughout the experimental period. We conclude that temperature increases may shorten the reproductive cycle of A. arenaria.