Atomic gardening is like playing with plants and radioactive materials. Scientists in the past used radiation to make mutations in plants, which means they changed the plants' genes in a safe way to make them better. They wanted to find ways to make plants grow faster, be healthier, and have more fruits or veggies.
Imagine you have a garden with tomatoes, but the tomatoes are too small or too bitter. Scientists would use radiation to change the tomato's DNA to make it better. It's like if you have a toy and it's not working well, you can take it apart and put it back together again to make it work better.
Atomic gardening is still used today, but in a safer way. Scientists can use radiation to make the plants pest-resistant, drought-resistant, or more nutritious. It's like giving a superhero costume to plants so they can be stronger and healthier.
So, in plain words, Atomic gardening is when smart people use tiny bits of atom magic to turn plants into super-plants.