For closure to occur, the trap leaves of the carnivorous Venus flytrap (Dionaea muscipula Ellis) normally must be stimulated twice. This is achieved by touching the bending-sensitive hairs protruding from the upper leaf surface. This triggers a rapid thigmonastic capture movement of the leaf lobes. This way incidental closure movements are avoided. The maximal memory time, i.e. the time limit between the first and the second stimulation event, which must not be exceeded, is highly variable and ranges between 20-80 s. Our investigation explores the influences of external (environmental) and internal (plant specific) factors on this memory time. Throughout in this study, a '50%-closure-value' was determined for each variable on basis of 50-100 independent measurements. The memory effect exhibits inverse and sigmoidal temperature characteristics, thus showing a maximum memory time at lower temperatures (15°C). Moreover, the daily photon fluency, the age of the trap leaves, seasonality (the time of leaf emergence), and the recovery time between consecutive stimulation cycles, all affect the time memory strongly. Further, the topology of stimulation also exerts a large influence: The time memory fades more rapidly when two different trigger hairs were stimulated successively within the time limits of the memory instead of touching the same hair twice.