I have butternut squash vines growing right up against a wood hydro pole that has been treated with creosote. The plants have done extremely well and there are about 6 ripe squash ready to pick. Are these edible even though they’ve grown up against the creosote-treated pole? Do the roots absorb creosote?
Wood doesn’t last long when exposed to the elements unless you take steps to protect it, and for many decades, creosote, which is a tarlike substance, has been used to protect wood used in outdoor industrial applications.
Research shows that creosote does leach out of the wood and into the soil, but worn-out wood is generally not a problem, because most of their creosote has already leached away. Whether plants take up the creosote has not been settled. However, because creosote is toxic, newly treated wood can cause growth problems for plants that come into direct contact with it.
One research study states that “Creosote that seeps into the soil may damage roots directly, but plants will not absorb the substance into their root tissue. Keeping plants at least several inches away from treated timbers usually prevents damage from direct contact and vapors, and creosote will generally not migrate far enough through the soil to reach plants that are a short distance away.” http://homeguides.sfgate.com/creosote-harmful-garden-77104.html.
There is no mention in the research how old the wood has to be before the creosote stops leaching, also the fact that your squash is planted directly next to the pole not the recommended 6″ away and The International Agency for Research on Cancer and the Environmental Protection Agency (EPA) have both found creosote to be a probable carcinogen, my recommendation is to play it safe and not eat the squash from this particular plant.
The following links give more information on creosote and it’s harmful effects.