Have no idea what Bumper Crop is so I can't help you there but yes, you bury the lower leaves and up the stem above them.

Dave

Thanks. Will hill around them and cover the lower leaves but not the growing top leaves.

each and every time you weed your plants us a hoe and bring the soil and weeds right to the plant and cover stem and leaves to the top of the plant. the plant well keep growing up. a friend uses car tires. as the plant grows he puts a tire down around the plant and fills it to the top with soil. in his garden i have seen tires five high. when he pulls the tires off at the end of the season they are just full of potatoes all the way up. good luck... JOHN