Carbon 14 dating for
The sample of the end result would be contaminated.
Plants get their share of carbon atoms from the atmosphere. It is seen that at any given point of time, the ratio of stable carbon and radiocarbon in the atmosphere, is almost same as the ratio of stable carbon and radiocarbon in living organisms like plants, animals, and humans.
When a living organism dies, its carbon intake ceases.
From that point onwards, the unstable carbon-14 decays with its half life of almost 5700 years, and the amount of carbon-12 remains the same.
"Dendrochronologists [scientists who study tree rings] have built sequences for a number of tree species, including German, Irish and Polish oaks, Patagonian cypresses, Lebanese cedars, pine, yew, spruce, and chestnut.
They've plotted rings from shipwreck timbers and roof beams, and wood from the Mediterranean, Russia, and China.