This display explains how plants regulate the time of day at which they flower, as determined by their circadian clock. Three key external factors regulate the plant’s clock and ensure it keeps to a 24-hour rhythm: sugars made during photosynthesis, light levels, and temperature.
The two beds in this display represent a clock. One bed contains plants which open in the morning and which attract familiar pollinators such as bees; the other contains evening-flowering species which attract evening pollinators such as moths. These flowers are often scented.
Some plants open their flowers at sunrise and close at sunset (such as Morning Glory), while others open at dawn but close just after noon (Jack-go-to-bed-at-noon). The Four-o’clock Plant opens its flowers in late afternoon and shuts them before dawn.