This is the 3615th most frequent Spanish word.
mató
"Mató" means "killed."
Here, 'mató' is used in the third person singular form of 'matar', indicating a completed action of killing.
El héroe mató al dragón con una espada.
The hero killed the dragon with a sword.
In this sentence, 'mató' is used figuratively to describe the negative effect of the storm leading to the death of plants.
Por desgracia, la tormenta mató muchas plantas en el jardín.
Unfortunately, the storm killed many plants in the garden.
'Mató' is employed metaphorically here to express the destruction or cessation of hopes.