A month before average last frost here in Ada, Ok. We are having rain 2 days a week and my new garden area is mud with 1" crushed rock. Should I remove all the crushed rock before tilling? The area is an old greenhouse bed with gravel path down the middle. I'd like to plant in 5 rows and 4 walkways, but the gravel is pretty thick. Do you think it will hurt to leave it and till the rows?