The grape harvest takes place at the end of September. When we were in Chianti at the end of September in 1999, the fields were full of people picking grapes. They fill up plastic containers, then carry them to the end of the row and dump them into a big open container that is pulled by a tractor. You see these containers full of grapes driving down the country roads. It is quite a sight. We could even smell the fermenting taking place when we walked by some farms.
The olive harvest takes place in November. We have never been there for an olive harvest, but would love to do this one year. If you rent the farmhouse apartment in Panicale, you can help with the olive harvest. Gun gives you some of her oil to use when you rent an apartment from her.
The chestnut harvest takes place between the middle of October and the middle of November. A couple of months after that, the fresh chestnut flour is available. There are many areas with chestnut trees in Tuscany.