I am in 8b SE Ga. What zone 8 are you? just planted sweet potatoes this week. Regular potatoes get planted Feb. 14 here. Turnips are a cool weather crop.

I'm in 8a (Pacific NW) and plant fall/winter turnips at the end of this month (July) or early August, depending on the weather. I never grow a summer crop because of root maggots. I hate messing with row covers, so I don't bother and keep my turnip growing to early spring and fall/winter. Just Right is the variety I grow for fall/winter, and I highly recommend it for growing in this area.

As for potatoes and sweet potatoes...I can't be of much help. This is my first season growing potatoes (I planted mine at the end of April) and I've never given sweet potatoes a try. I do believe (someone correct me if I'm wrong!) that depending on where you are and what your late summer and fall seasons are like, you may still be able to give a fast maturing spud a shot. If you have a rainy season coming up in the next few months, then it's probably not a good time to plant spuds. Good luck!

In this part of Georgia turnips can be planted late August until October 15. Irish potatoes early February. Sweet potatoes should transplanted in May although sometimes I plant in late April. June is about the latest.

I'm in Portland, OR (8b), and I planted turnips, carrots, and daikon radish last weekend.