In my not-at-all-vast experience growing sweet potatoes, they take a LONG time to mature, so you just have to be patient. Since they're in a raised bed you can peek at them and see how they're doing before deciding to dig them up. They might not be huge, but they shouldn't be spindly. Last year I didn't re-root any of the stems and let them climb all over the garden and ended up with cute little sweet potatoes 20 feet away from the original plants. When I went to till this spring, I found more.

My problem seemed to be lots of different problems (or just plain bad luck?). One year the slips that came in the mail were beautiful. I put them in water for a few days, planted them out, and they grew well and I had a successful harvest. One year the slips that came looked dead (and in fact were). I put them in water right away and they never perked up. This is the extreme negative experience I have had with attempting to grow sweet potatoes. Other years the slips came all wilty, as is typical. Some would perk up in water, some wouldn't. I planted them out and some would die and then a few more would grow for a while and then die. This loss through attrition seems to be the biggest problem I have had. The ones that survived would produce disappointing harvests of a few small sweet potatoes. One year I planted them out and they were growing nicely and then our wonderful desiccating prairie winds destroyed the young plants in one hot, windy day. They never recovered. Another year the young plants drowned due to too much rain. I have rich heavy clay loam soil - not the greatest for gardening due to water retention and compaction but it is incredibly nutrient-rich. I have my soil tested every other year and amend accordingly. The soil is slightly but consistently on the alkaline side. I do not know if that is a problem for sweet potatoes. Two years I suspect were my fault - planted slips in too-cold soil temps - but I planted out when my experienced neighbors planted theirs and they told me to go ahead and plant - no joy. I have ordered from reputable catalogs (they just contract with the same supplier don't they?), and I have ordered from the same company that a neighbor orders from - no real success with any. The one company I really should consider ordering slips from is Sand Hill. Glenn and Linda have quite the collection and they are in a similar climate as me, and are somewhat close geographically which should reduce shipping time and thus stress on the slips. I could get some short-season plants from them to try out. I welcome other suggestions for suppliers. I have looked into purchasing organic sweet potatoes for producing my own slips. A viable option but often the employees do not know the correct names of the varieties - unhelpful if they turn out to be long-season types. BTW the one neighbor of mine that consistently grows good sweet potatoes just lost over three quarters of his plants to deer browsing (he planted 100 plants). In a fenced-in garden (they jumped over). Needless to say he is quite disgusted (putting it mildly). I feel bad for him. This is THE crop he loves growing and he is rightfully proud of his accomplishments. Sometimes you just can't win. Thanks for all the comments folks, they are appreciated and are being taken under advisement.

They say don't put the starts out until June but I always fudged a little, like May 1-15. The ground is usually warm by then. You can get sweet potatoes now or in a month, they get harder to find in a store the longer winter goes on. Make some notes of dates etc for next year, your mileage may vary, as they say. They will root stuck halfway into a glass/jar of water or laid on the side half buried in a box of moist sand. It does take a while for them to start and hard to say but you might average 10-12 slips per 'tator. They will have long roots if you use water so spread them out when you plant.

I have plenty of home grown, organic sweet potatoes that you could grow slips from. They are a cultivar called Murasaki, purply-pink skin with white flesh and great flavor. I would be excited to try a short season purple-fleshed sweet potato, but anything home grown I would be interested in hearing about. I am open to non-sweet potato trades, maybe check out my want list at http://members.gardenweb.com/members/exch/infiniteohms