Thanks for the question.

Sweet potatoes generally thrive in fertile, well-drained soil. Generally a 10-10-10 or 14-14-14 fertilizer is used. However in fertilizing sweet potatoes timing is all important. Hence the possible difference between your thoughts and those of your friend. The best approach is to apply the fertilizer before planting and again once during the early part of the growing season. This would generally be about six weeks after planting. If you fertilize while the potatoes are actually being formed you may stimulate vegetative growth at the expense of developing size in your potatoes. In this regard your friend does have a valid point.

With respect to hilling them up, this generally occurs about 4 – 6 weeks after planting. Before hilling up, there should be signs of vigorous growth in the plants. Remember that a major purpose of hilling is to encourage the development of additional roots. These, then, help to increase the yield and quality of the potatoes. Generally additional soil is used for this hilling. The mound should be around 4 to 6 inches high.

Good luck with your plants. Your beds look fantastic! Please get back to us with any further questions.