Oh! So interesting that you asked about this. My Dad used to grow them every year. When he first started, he contacted a farmer in Japan to get detailed instructions on how to grow them and asked me to translate a list of livestock meals that were to be used for fertilizer — soybean meal, cottonseed meal, alfalfa meal, bran, etc. Unfortunately I never found out how he grows them though... mostly because my garden isn’t suitable.
My parents moved into assisted living last year and we are selling their house. I’m at the point of last minute saving/salvaging before the house is put on market ... and even though my Dad’s garden has been neglected for the past couple of years, there may be some vestige of the wild mountain yam left in his garden.... and I have been trying to decide — try to save or not.
Knowing what you have described about your garden, I’m not sure that you will be successful — these grow deep and hardest part is harvesting them — you dig a deep trench alongside the row and excavate them like you are at an archeological dig. My dad always said if the soil in his garden wasn’t so sandy, it would be impossible to dig the trench this way or extricate the tubers without breaking them. He also grew them on a sunny slope for good drainage (despite the sand).
Even though I would love to continue his hobby in his stead, I’m pretty sure my own clay subsoil garden with hardly any area that provides good drainage is suitable.
I didn’t read the link you posted closely — maybe everything is explained? — but if I remember correctly, you can grow new plants from the roots like you do sweet potatoes. In this area, the vines will freeze and die and even the roots can be feeeze damaged and need to be dug up, though some of the missed roots survive.
Another thing — the vines produce small round, aboveground, marble-sized ... I don’t know what this is called .... You can use these to grow new plants next year. They develop tough skin and can be saved over the winter. But when freshly harvested, the skin is tender and my parents used to cook them in with rice or put them in soups and such. These readily fall off the vines and will also sometimes survive the winter and grow new volunteer plants in spring.
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