Answer: That is puzzling. Usually gardeners have trouble keeping things from growing up and taking over their chain-link fencing! Perhaps the person who installed the fence added something to the soil to keep weeds from growing on the fence, or they had a pet dog that patrolled the perimeter, and through their constant pacing, compacted the soil so that nothing will grow. The only way to find out for sure is to have the soil tested. Here in Vermont, a regular soil test performed by the extension service lab can test for heavy metals and other toxins, but I'm not sure what services Maine extension offers. You may have to enlist the service of an environmental lab.
If you don't want to go through that process, you can build wooden planters to place at the foot of the fence in which to grow your vines and sunflowers. Best of luck to you!
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