And the end result...the "knot" come harvest time.
Edited to add the article I wrote, could not find the darned thing.
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Easy Growing Sweet Potatoes
Most people probably don't realize how easy it is to grow your own sweet potatoes, how well they tolerate growing in high heat and drought-like conditions, how well they keep and the high yield you can get from a single potato.
Someone told me how easy they were to grow, and I decided to find out for myself. I took photos along the way to share my experience with others. This is just an account of how I did it with almost no instruction from anyone, so you may alter it somewhat to fit your needs.
First, I simply purchased a few small sweet potatoes at my local food store. They don't need to be large as you are just acquiring these to grow "starts," as you don't plant the actual potato. I then took an empty 2 liter soda bottle, and cut it down to leave it a little over half size . (fig. 1) This allowed me to see how the rooting progressed over time and made it easier to photograph them. Place your potatoes inside, and fill with water to cover them about 3/4 of the way. You don't want to submerge them. (fig. 2) Place on a window sill to give them some light and to watch their progress. I started this about 6 weeks before I planned on putting them in my garden, enough time to get them ready for planting.
Soon you will see them start to root out, and buds or "starts" will start to form on the tops of them. (fig. 3) Be careful if you handle them as the starts can easily break off at this time. They are similar to "eyes" on red or white potatoes. As the roots come out directly at the bottom of the individual starts over time, make sure you keep the water level just above there, to encourage root growth at the actual starts themselves as this is what you need.
After 6 weeks of time, they look very lush as the starts turn into vines and the roots are thick. (fig. 4) Keep water level maintained as they are really using it up by now, and make sure they get a lot of sun in the window area you have them. At this point you can either transplant them into their own small containers to let them grow a little larger, or plant them directly into your garden.
The soil needs to be a warm temperature for planting. If it's too cool outside, wait to plant. In other words, the warmer the soil the better for sweet potatoes. If the soil temperature during the day is below 80 degrees, they probably won't grow.
Prepare a place in your garden for them. They need the soil mixed with sand on a ratio of 1:1. In other words, half soil, half sand. Regular soil is too hard for them to expand and grow in. (However if you live in an area like South Florida or some other geographic location with sandy soil, you may be fine just planting them directly.) Dig a hole roughly 16 inches in diameter and two feet deep at the minimum. Mix the soil and sand well. Space 40 inches apart.
Carefully pull your sweet potatoes out of the bottle and separate them. You can see how most of the starts are barely hanging on to the potatoes at this point, with their own healthy vine and hearty root system. Carefully break a start off the main potato, taking care to not damage the vine or it's root network. (fig. 5) Plant this directly into the prepared area, carefully letting the roots drop straight down and backfill carefully. Keep them soaked the first couple weeks until they get established.
Once they get established, they tolerate the heat well. Water with the rest of your garden, and the vines will tend to dry up somewhat and by the fall they may break off, but the potatoes will be fine under the ground. Dig them up carefully before you get your first frost, making sure not to snap them or gouge them with a shovel. They will be clustered together in a large "knot." (fig. 6) Don't scrub them, but take a hose and rinse off the clods of dirt, then place them in an airy container like a milk crate and store in a cool, dark place. We dug ours up over seven months ago, and they look, feel and taste just as fresh as the day we dug them. Save some of the "straggly" looking ones for next year's crop.
We had one of the worse droughts on record for the 2012 growing season, but the sweet potatoes did phenomenally. The "knot" in figure 6 grew out of one small start, and there can be as many as 20 starts per potato. We got all the sweet potato plants we needed from just a single potato!
Good luck and happy gardening!!
