Jengc - I'm gonna direct some of the sweet potato growers from the vegetable gardening forum to this question, because I feel they will have the best answer. I'm wondering about it myself, because I pulled a huge cluster of them last year that were all skinny.

EG

Cool! Thank you very much. I didn't think about putting it in the Vegetable Gardening forum. :D

Sweet Potatoes need good drainage and long hot summer.
However, it doesn't like too much fertilizer and clay soil. If the soil is too fertile, Sweet Potatoes grow only leaves, not tubers.

Try grow Sweet Potatoes next year on raised beds to solve the drainage problem.

If you plant sweetpotatoes in a leaf pile, they will grow long and stringy. So, they like real soil.

The original poster did not divulge what variety was planted, when, and what more... except "loose soil".

I did not realize there was a variety. I bought a sweet potato from the grocery store and used the shoots off of that. Loose Soil means soil that is loose. Meaning it wasn't soil from the ground and wasn't compacted. I am not sure of the precise ingredients I used to make the soil, but it was a form of dirt. Things like compost, vermiculite, and peat moss. I think I threw in a little soil in a bag from Walmart, but I can't specifically recall since this was last year. I hope this was specific enough.

Based on what Wayne said, I can contribute that my skinny tubers were because of the unfinished leaf compost that they were planted in.

EG

That wasn't my problem. Now my compost today might have that problem...unfinished leaf compost....but not last year. While I didn't go straight by Mel's book, it was the same soil that I most all my plants in. The Irish potatoes were kinda puny too now that I think about it. I think we got maybe 10 full sized potatoes and the rest looked like new potatoes but they were in the grown the full time and the flowers were half dead.

I don't know what the deal was but I am going to use new soil. I did pull them up before the leaves died out but first frost was coming soon.....plus I wanted to have one! :D

Size of Irish potatoes is related to spacing. Close spacing = smaller potatoes. Wide spacing = larger potatoes.

I don't know if this applies to sweet potatoes.

Jim

sweet potatoes have to be planted at the right spacing and it is variety dependent. Jewel for example needs about 10 to 12 inches between plants and 5 feet between rows to make a crop. Okinawan does best if at 2 feet between plants and 5 feet between rows.

As noted above, compost, manure, and fertilizer are verboten with sweet potatoes. There is a minimum level of fertility that they require, but it is much less than most other garden crops.

Golden Nuggett does a really good job of producing plump potatoes where recent introductions such as Beauregard tend to make long skinny roots. Check the variety you are growing to make sure it has the tendency to produce the type potatoes you want.

DarJones

I have been experimenting in that zone of extremely little fertilizer, in florida sand. Also no irrigation or weeding. Also planted like irish potatoes, from tubers. Trying to control for all of these factors over several years, my conclusion so far is that spacing is the most important factor in avoiding wispy, very small and huge fused tubers (which is basically all you get if the vines are crowded).

I also find that the southern varieties grown in that poor sand have greatly superior flavor compared to northern ones grown in much more fertile soil.

Wow! So spacing might be a problem. OK I followed Mel's recommendation, but I also know that he did not invent nature. That was God's doing LOL

OK then, I will space out more. I mean why crowd when you can get more, for less seeds!

I have no idea the type of sweet potato. I bought the original sweet potato at a grocery store (which would have given me the type!) but that was last year. I was able to save one from my bounty last fall (I couldn't believe it myself) so I still won't know. I think I planted 8 slips in a 2x8 bed. They didnt seem crowded, but you know sweet potato plants. They grow crazy! Maybe I should just plant 4 plants in the 2x8 bed?

pnbrown-from what I am reading, you are saying that soil that is not as good would grow better potatoes? I have horrible clay soil but I do have a patch that has been worked and amended over the years. It has been at rest for a few years and thought about tilling that up. So of course, it wont be like the other soil in my back yard. Much less clay-ey (is that a word?). Anyway, I know that it isn't near as "good" (meaning less nutrients) as the soil it was originally grew in (which I do know you are not to re-use the soil with potatoes due to possible diseases in potatoes) so would this be an ideal place for potatoes?

Also, I thought I read where you can cover the potatoes with straw or some other material like that (maybe mulch?) instead of soil. Is that true?

Thanks for all of your advice!! You guys rock! :D

I have heard the same thing about covering the potatoes with straw and letting them grow there instead! From what I remember, it was recommended to add straw (NOT hay) gradually til you reach a 12" depth. Obviously that's going to take a little doing if you're growing them in a SFG. I was actually looking for more info on that technique when I came to this thread.

I read about this on another web site (ask.com I think) and it said it was fine as long as you don't have a pest problem. While we occasionally have mice visit I don't know if this will attract them. But it will be MUCH cheaper to buy straw than soil. I guess the plant gets it's nutrients from the soil at the roots like any other plant! I guess I am stuck in the idea that potatoes are a root vegetable which is not true. Sweet potatoes are however.