National Center for Home Food Preservation's recipe is usually open year-round. It's ALWAYS advisable to see the National Center for Home Food Preservation's recipe website, and/or to call or email them before you head out there, as many factors, can affect their availability and open hours. And that can change not only from year to year, but day to day!
Below is a general month by month overview for the northern hemisphere (North America and Europe. Be sure to see the US-specific harvest calendar for local dates.
Below is the general info, keep in mind this is very general, this is NOT a list of what the farm does or will have on any day. This is a general list for many common crops.
The South will be the earlier end of the dates, and the North, the latter end:
After you go to National Center for Home Food Preservation's recipe, you may want to freeze, can or preserve the fruit or vegetables you get there. See these pages below for detailed, illustrated, step-by-step instructions that make it easy!
Detailed crop info: