This is the 4267th most frequent Japanese word.
健やか
Healthy; sound.
In this example, "健やか" pertains to the condition of healthy and robust growth, applied to a plant.
その植物は健やかに育っている。
That plant is growing healthily.
In this sentence, "健やか" is used to describe the mental health or state of being clear and sound of mind.
彼は健やかな心を持っています。
He has a healthy and sound mind.
Here, "健やか" illustrates the physical and emotional health in the context of growing and developing.