How do you get rid of grass on Harvest Moon DS?

I'm not sure which 'grass' you mean. ok, I'll provide answers for all.

1. The grass that you have to buy seeds to grow.

Ans: Use your Sickle to cut it when it is full grown, then you use your hoe to plow it.

2.The grass that you find on lands, different colour for each season.

Ans: Either use it for making food or just eat it.

3. The grass which is also known as weeds.

Ans: Pick it up and throw it on the ground, it will disappear. Or use the sickle to cut it.