I've been saving the same sweet potato vine for several years now, I take several cuttings in the fall and grow them in pots in the house, and use them again the next summer in my containers outside. This winter the cuttings did not do well, but most survived and finally started filling out when I replanted them outside. But I notice now that the leaves are more yellow than they ever used to be. Anyone have any ideas why? Do you think it's a lack of fertilizer? I did put some plant tone in the pot about a week ago. The first photo was taken this morning, the second one was a pot from 2 summers ago, but the exact same mother plant.
Cindy, I find that there is always a variety of color on sweet potato vine as well as other plants. I overwintered 2 dark vines that did OK in their pots, but I always do best when I use packaged potting soil. We have also had some really unusual weather for this time of year, and I notice that although the nights are warm, we're not getting the amount of growth I have expected from most of the annuals. Bulbs and corms have started to take off as have some of the tomatoes, but sweet potato vines, coleus plants and celosia have not done much. Even the petunias which tend to spread nicely are going more slowly than usual.
You might try moving the pot to a less sunny spot, although the flowering plants might not like it. They don't generally need as much nitrogen. If you have two plants in the pot, which is what it appears to be, try taking out one, putting it in fresh soil and putting it into another location.. The one thing I have noticed this year is (a) an abundance of chipmunks and (b) and abundance of disturbed soil in my newly potted containers (and I'm really getting sick of that). So, did you check for "critter" trouble that might have affected that container and specifically that plant? I bought a variegated sweet potato that is planted with coleus, and it always seems to be dug up, so I don't know what is going on with that.