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I bought some purple yam from the Asian supermarket. I think they are true yams because there's laws for correct labeling of yam versus sweet potatoes.

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Cut open one end to show you the purple flesh inside.

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My question is how do I grow new yams from these? I've been reading some online articles and I'm hearing some confusing information:

  • One website said you you can use small tubers. From the pictures, I don't believe I have any tubers.
  • One website said all yams in USA are actually sweet potatoes because they can't grow in USA. So they suggest to grow like sweet potatoes by submerging half in water to grow roots and slips. But what if this was imported from another country and this is a true yam? Is the growing process different?
  • One Youtube video said to cut an inch off from the end that has roots and put the roots pointing down into soil. Then cover with two inches of soil. Looks like I only have one yam with two tiny roots. How would I be able to grow the ones without roots?
  • No one really mentioned how to water them as they are growing roots. Do they like moist soil or drenched soil?
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Growing vines from store bought yams and potatoes is relatively simple, it just takes time and patience. I've grown multiple vines from a variety of tubers. From the looks of it, you have sweet potatoes, not yams. Yams have rougher skin and are more cylindrical in shape. It is not unlikely for a sweet potato to be mislabeled, law or not. Plus, there are purple sweet potato varieties. Luckily, sweet potatoes are easy to grow!

A couple notes to start:

  • You do have tubers. A tuber just means the swollen part of a plant's root system (the potato or yam), which holds the nutrients for the plant's growth.
  • The growing process for a yam and a sweet potato are the same (or, very similar), because they're both tubers. So even if I'm wrong about your tubers, the same process should still work.
  • Fun fact, they are not related. Sweet Potatoes are in the Morning Glory family, and Yams are in the Lily family. Also, potatoes are in the Nightshade family... don't eat any berries that grow on potato plants!

Most of your tubers will grow roots eventually, but you can start with the one pictures that already has a root or two. I've had more success not cutting pieces from my tubers, even though a lot of sites recommend that (mine rot quicker when cut, so the plant doesn't get the nutrients it needs). Here's some steps to take now:

  • Place the tuber in a sunny spot, suspended with the root end in water. (Take a large jar and fill it part way with water. Stab some toothpicks in the upper end of the tuber, so they support it on the rim of the jar, while letting the bottom end sit in the water.)
  • Let it grow! You'll see more roots grow, as well as "slips" on the top. The "slips" are the vine portion of the plant. They'll look like roots to start, but will grow upwards, and develop leaves.
  • Once it has 2-3 slips (or more, or less, it's not hugely important), bury the tuber in a well draining pot with fresh potting soil, and keep the soil moist (don't soak it, or the tuber has a higher chance of rotting). I water mine about 1x per week, but that may vary.
  • I find my sweet potato vines grow very quickly. You can let the vines grow indefinitely, or, for a fuller plant, cut the vines occasionally so it grows more shoots instead of longer shoots. (You can put cuttings in water to root them!)
  • How do I know which part of this potato is a tuber and which is not? You say it’s the bulb tumor-like shape? What if my potato is a rather homogeneous looking like the 2nd to top one in my photo? – JoJo Apr 29 '19 at 20:49
  • @JoJo good question! The tuber is really any large root part, so it’s not part of a potato, a tuber is the potato. So anything you buy at the store is a tuber. Basic parts of a potato or yam plant are the vines above ground (with leaves, flowers, berries) and roots underground (roots and tubers). We eat the tuber part. – Gwendolyn Apr 29 '19 at 21:11
  • I've had pretty good success with cutting an orange sweet potato in half, then putting the cut side down into the water. See my photo: imgur.com/J23FvQz . The only problem I see is weird moldy milky looking thing developing on the cut. I've also seen people not cut the potato at all and dunk half of it in water. It seems to grow more vigoriously whole. I'll try it whole this time and see how it goes. – JoJo Apr 30 '19 at 5:10
  • I've been trying to pinpoint what exact sweet potato I have. After comparing photos on Google image search, it appears I have the Okinawan Sweet Potato. Odd that this grocery store labeled it generically as "purple yam". I would assume anything with a Japanese name would give it a more premium feel. – JoJo Apr 30 '19 at 5:27
  • @JoJo good call! After googling photos, I’d agree. Best of luck growing them! – Gwendolyn May 1 '19 at 2:41

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