Hi greensleeves,
Afraid I can`t help on the potato query, but as for kale I highly recommend cavalo nero, (seeds of Italy sell the seeds) If you are quick they should grow away all right & give you tasty leaves right through till spring. I sow mine at the end of July for planting out now we will be cropping the leaves from the end of September. They are like cut & come again salad leaves , just pick a few leaves at a time from each plant.
Adrian.