An event can be predictable, in the sense that we know that it will happen in a given set of circumstances, or predictive, meaning that it is a precursor of some future happening.
The behaviour of some plants is alleged at times to be predictive, but invariably the organism is merely reacting to the environment in which it finds itself.
Almost always, too, there is an advantage to the plant in reacting in the way it does. Let me explain.
Some flowers, like tulips, gentians and crocuses are sensitive to temperature. In the gentle sunshine of the early spring, the open petals of the first flowers trap the heat like little solar panels. It is thought that the few insects on the wing around that time may find this warmth appealing, so the heated flowers are a welcome invitation.
The insects fly from heated flower to heated flower, pollinating as they go, and thereby doing the little plants some service. However, even the passing of a spring-time cloud may cause the flowers to close.
Other plants are sensitive to moisture in the atmosphere.
The familiar bindweed Convolvulus arvensis, for example, closes its flowers in daytime when the humidity rises with the approach of rain.
The marigold, Calandula pluvialis, also has this gift as, indeed, its name implies, and so does the common dandelion or Taraxacum.
Similarly talented, perhaps most famously of all, is the little scarlet pimpernel, often called "the ploughman's weather-glass".
Armed with such observations, it was not a major step for our ancestors to impute predictive powers to certain flowers and shrubs - the belief, for example, that "the daisy shuts its eye before the rain". And in the case of the scarlet pimpernel, its alleged rain-predicting capabilities have been celebrated more than once in rural rhyme.
One such ditty, tells us of:
The pimpernel, whose brilliant flower
Closes against the approaching shower,
Warning the swain to sheltering bower
From humid air secure.
There are sound reasons, of course, why these flowers react to increases in humidity.
They do so to avoid their pollen getting damp and germinating prematurely. And the closing movement can be very quick; the unfortunately named Bastard Toad-flax, for example, also more politely known as Thesium alpinum, closes up within 30 seconds of being moistened.
Unfortunately, the reliability of any of these flowers as weather forecasters is marred by the fact that they close up anyway at night, and they also respond to the dampness of a fog or mist in otherwise dry and very settled weather.