Calculus is a tool that helps us understand how plants grow by looking at how things change over time.

Let's break it down:

1. Growth Rate: If we think of a plant's height as $h(t)$, which shows how tall it is at different times $t$, the growth rate is shown by $h'(t)$. This tells us how quickly the plant is getting taller at any moment.

2. Area Under the Curve: We can use integrals to find out how much a plant has grown over a certain time. This is like finding the area under the growth line on a graph.

By using calculus, we can study and even predict how plants will grow!