Just Dioscorea

Jim McKenney jimmckenney@jimmckenney.com
Fri, 02 Jul 2010 08:12:08 PDT
I'll bet the one in your garden is Chinese yam, Dioscorea oppositifolia
(widely known as D. batatas). It's a terrible pest in many areas and is
widely considered to be "officially" invasive in some states. This species
forms large tuberous roots and small aerial tubers. I've never seen a
variegated form however. This species and D. japonica are similar, although
web photos of D. japonica show very upright conspicuous spikes of flowers.  

The ones you saw with big aerial tubers might have been D. bulbifer.
According to the wikipedia account, the tubers of this one range from edible
if boiled to toxic. It is probably not hardy northward but is feral in

Jim McKenney

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