Yeah, there's no real easy way. But you do have to get the roots out or they'll sprout right back up. You may turn a hose on and let it saturate the ground to make it easier to pull. Then when it's good and soaked, start in one corner and work your way around methodically.

Take breaks when you get tired but come back and do more. It may take a day or two or three days, depending on the size of your planter, and your energy and time limits. I used a spade and pick-ax. It was grueling but satisfying when done - and much better planting.

I couldn't do a tiller because the size of the planter rows on mine was too small to try to wield a tiller.