Texas Gardening: ID this weed??, 0 by Dogs_N_Petunias

Dogs_N_Petunias wrote:
This vine weed started getting bad in our area in the last couple of years. Hit our place last year and spreading with great speed this summer. It seems to be almost immune to RoundUp. Burning it with propane torch is effective but terribly time consuming. I certainly hope it isn't a host plant for butterflies because we just can't stand this stuff all over our fences. Anyone know the name of it?