The first harvest festival that witches celebrate/particpate in is called Lammas--the wheat harvest. It's held on August 1st. It is customary for a loaf of bread be made from the new crop and be blessed. It is broken into four parts and placed at the four corners of the barn to protect the grain.
With grocery stores filled with food and anything we can get any time we desire, most people forget that harvest festivals were celebrations that there would be food to eat over the winter.
People had to learn how to preserve. Witches, too. The three most common methods are as follows:
Freezing -- the easiest. Clean, blanch, and freeze.
Canning - more involved, but easier to store and energy-efficient. Water method and pressure canning are the most common. Fruits, vegetables and even meats can be canned successfully.
Drying - for jerky and fruit. Requires a food dehydator.
Many witches like to celebrate Lammas by preserving their own food. As part of the ritual, they bless the food as part of celebration before perserving. They ask the gods and spirits for blessings on future harvest activities. They aren't just celebrating someone else's harvest, but participating in their own.
Do you can or perserve your own food?