I guess I do not understand how sweet potatoes work. I planted 3 sprouting sweet potato chunks several months ago and this is what I have but when I pick up the vines they seem to just lift off the ground. I thought that as the vines grew they would put down roots that would turn into sweet potatoes but I do not see that happening.

What am I missing here?

Thanks.

Nothing, sometimes vining sweet potatoes do put put down roots from vine nodes. It usually occurs late like 100+ days after transplanting . Not all those roots enlarge into sweet potatoes tho. In modern releases most of i the storage roots will be close to the base especially, if the plant is elevated aboveground (hill).

Thanks. So can I just trim all those vines back since they are taking over the raised bed?

It will reduce your yield, since it is the vine which which gathers the energy and stores it in the roots. Check to see how many bases you have. If the plants are crowded at the base, they will be be mostly vine with few usable roots. Hopefully you only have three plants in that space. Vining plants can run 8-10 feet from the base. If you grow sweet potatoes in the future you may want to consider bunch/bush varieties.

You might be able to see the tops 0f some tubers right near the base now.

It looks like you're using a growing mix of some kind so it should be soft enough where you could dig a little away and see if you've got tubers down there. Naturally you'll have to find where you planted the sprouting chunks at and dig there. I've had vines to peg down in the past and grow a few taters but the bulk of the harvest will come around where you planted the chunks. Usually "slips" are planted, basically six to ten inch long sprouts that are broken off the potato, placed in water until roots appear, and then planted. Most people purchase slips but they can be a DIY project, only problem is that you can't be sure the DIY version is disease-free. The little "slips" seem so fragile and weak but they will surprise you with their quick growth.

You're vines look pretty healthy, though the ones on the left side of the bed look a little light colored. ???

Be careful when you harvest and don't nick/cut the tubers. Usually they'll scab over and be ok but cuts can allow rotting to start. Also, you might want to read up on curing and storing the tubers. Don't wash them. Let them dry well. Cure in a warm 85-95 degree area...store them in cooler temperatures later. Scroll down not quiet halfway on this webpage and you'll find some information on curing them... https://www.almanac.com/plant/... ...or just google "curing sweet potatoes".

Be sure and post some pictures of when you harvest them....it will be interesting to see how good your harvest is.