SP production doesn't depend on air temps - it's soil heat that matters. You need a certain number of hours at a certain high soil temp - it's like degree days in home heating. I forget the number, but you multiply temperature by days to get the number. The good thing is that you can raise the temperature of the soil with plastic. Get the soil smooth, and lay the plastic tight against it to get the best heat transfer - no air pockets.

Rosie, these are so easy to grow and have a huge ROI for our frequent consumption. I usually dig them at the end of Sept here in ctrl KY. Begin digging two feet from the plant, especially if raising V. They are then placed on cardboard on the stone sun porch floor and covered with burlap and bask in the heat for at least 3 weeks. I keep the windows closed to keep it extra warm at least in the daytime. Next, I gently place them in two layers in cardboard boxes, and drape two layers of brulap overtop. Usually I sort them size wise. These boxes are then set on the downstairs floor (concrete with two inches of insulation underneath), where the usual temp is 60-65 deg. When winter sets in, I often bake a jelly roll pan full when baking bread, and then process some for freezing for pies, soups, mashed SPs, etc. A few months ago, I began snapping sprouts off last years crop, and do it monthly now-but they are still very tasty. Enjoy-now if you have secrets for raising organic peanuts, I am ready for them!

You need a soil test to be certain what's going on with the ground itself. No amount of guessing will help. Tell them what you're trying to grow and they can offer corrections tailor made for specific crops, usually. Generally, you need softer soil so the tubers will be able to expand. Incorporate all the organic matter you can find. Compost is supreme, but chipped leaves are great, manures are good, and if you absolutely have to, try peat moss. Someone suggested sand to me, but I believe that red clay plus sand = concrete and I don't want it to be worse than it is already. I plant about 300 slips per year. I do the same thing every year. I get varying results and still don't know why. Last year, I had a decent crop, but not any huge tubers like in the past. So this March, I hauled in fresh horse manure and dumped it and tilled it in. When I was ready to plant in May when the slips arrived, that had mostly rotted. I use a turn plow to make hilled rows. It digs deep. I go both ways to make one row so it's uniform on both sides. Works for me. Then I'll go back and hand plant 18 to 24 inches apart and firm the soil around them on top of the ridge. I make a depression around them to help catch water. Otherwise, it runs off, not in. Red clay forms a crust in a heart beat. I'll water a few times as is, then I'll go back and poke holes in the hill 6 or 8 inches deep and water again into the holes so water gets into the hill. Usually I have to water 4 to 6 times, once every other day, before it rains enough and the plants look like they will survive on their own. I may go 3 days between if it's overcast and not so hot. Watering is done by hand. I'm not near a spigot. Used to be 2 gallon cans filled from a rubbermaid container and spritz each plant. Now I have a 300 gallon tank on a trailer and a hose. I still walk the rows, but I can give each plant more water at a time without fear of running out so soon. 300 plants means about 500 row feet. last year, I dumped a quart of fish emulsion, a bottle of NOG, and a small bottle of chelated iron (needed magnesium or manganese, I forget) and just for good measure, a handful of 20 mule team borax for boron. They need boron. I added 200 gallons of water. Nice fragrant cocktail. I watered both the sweets and the tomatoes and pepper transplants with it. I had the best pepper production I've ever had. Sweets, not so much. This year, I added fresh manure in March and watered again with the cocktail. I dug sample sweets early last week that were the size of gallon milk jugs. Literally. I'm waiting to dig the rest another week or two. I usually dig them right at the September/October change. I've had rabbit issues this year from what I can tell looking at the patch. But the vines are thick and heavy, the leaves are huge. I'm looking forward to the big dig in another week or two. Next year, I should be using rain water. That's the plan anyway. See if this works. If not, click the link below. This is from two random plants near the end of the rows. Smaller regular size tubers are in the bucket... Here is a link that might be useful:

"I may put a 2 foot bamboo stick next to each plant when I plant them, as a marker." That's a good idea for many plants, especially those that need to be dug and those that vine. I try to do that with all my squash and cucumbers. It helps a lot when hand watering. Watering vines far from the roots doesn't do much good.