Effect of Rainfall on Ornamental Flowers

April 26, 2022


Photographer: Menashe Davidson  

Summary Author: Menashe Davidson 

Many researchers, including Charles Darwin, have speculated that flowers may have evolved certain traits or structures to protect themselves against the damaging effects of rain, which can wash away pollen grains and dilute nectar. This finding could explain why many species in rainy areas either have droopy flowers or close their petals.

The photos above were taken in my home garden in Rishon Le Zion Israel, on December 21, 2021, following a stormy day with 2.75 inches (70 mm) of rainfall. Three ornamentals' flowers, adjacent to each other, demonstrate different traits regarding their reaction to the rainfall.

At center is a petunia, genus in the family Solanaceae. Without any structure or trait to protect itself against the heavy rainfall, significant reproductive damage was caused. We can see that the petals are considerably withered.

At right is a cyclamen, perennial in the family Primulaceae. With a flower shape in which the sexual organs are facing the ground, the pollen is nearly completely protected by the flower structure. At left is a narcissus, perennial plant of the amaryllis family. Here we can that temporal bending of the flower stalks changes the orientation of the flower to protect its sexual organs.

On the collage at bottom, pictures of the same species were taken 4-days later, on the first sunny day after the storm event. I was astonished by the revival of the petunia plant! A new, gorgeous flower had just opened. Note that the withered flowers were cut.

As can be observed by their vigor, all of these plants seem to be positively responding to the increased soil moisture and the sunshine.