Do all flowers close up at night?  Although many flowers close
up at night, not all of them do. Those that open their petals
during the day and then close them at night are reacting to
light or temperature changes. Some flowers, such as tudaylilies,
remain open for twenty-four hours. Other flowers have unusual
opening and closing habits. Crocuses, poppies, and morning
glories, for example, open as the temperature increases during
the day and close as the day gets cooler in the late afternoon.
The flower called the four-o’clock closes in the morning and
opens again late in the afternoon, right around four o’clock.
Moonflower, night-blooming jasmine, evening primrose, angel’s
trumpet, night phlox, and night-blooming cereus open only at
dusk or at night. Some plants also react to touch and close up
their leaves and “play dead” if a hand or twig brushes against
them. For example, if you touch a mimosa plant, it will fold its
leaves and the stalk will droop.  Flowers close their petals at
night because they are pr