Unfortunately, USDA minimum winter temperature zones don't tell the whole story. In the winter and spring, its it sunny and mild between cold fronts, or cool, damp and gray most of the time? How often does it rain? Does it snow much? Does the ground ever freeze in winter? Is the ground too muddy to plant in until late into spring? Also, what are the day lengths like? Climate zones notwithstanding, the latitude of extreme southern France is roughly the same as Albany, NY, and the latitude of northern France is about the same as Spokane, WA. So the winter days are going to be short and the winter sunlight will be a lot less intense than we have here in North Florida.

The very best thing you could do is befriend a local gardener and ask WHEN the proper time is to plant. Try to get seeds for local vegetable varieties, because they should be better adapted to the climate and soil. (Actually, if you can get the local seed packets translated, they might tell you the recommended planting dates!)

There are some cool season crops that mature in 45 days or less - radishes, and beets, many types of lettuce, green onions, some kinds of spinach, and some greens for example. Also some of the cool-weather herbs like cilantro would get big enough to harvest leaves in about that time. You could probably harvest these by June in any part of France except in the mountains.

However, if you are in a warmer area of France and can plant cool-season crops at least 75-90 days before you leave, then you can grow almost any cool season crop - peas, carrots, large radishes, broccoli, cauliflower, and any kind of greens. (Two cool-weather crops you probably can't grow are Brussels sprouts and parsnips, because they take over 100 days.) If you're in a southern area, you might also be able to get new potatoes. Don't forget cool-weather herbs like parsley. You can also plant cool-tolerant flowers such as pansies, petunias, sweet alyssum, and snapdragons.

But I would guess that you won't have time to get harvests from warm-season vegetables (corn, tomatoes, eggplant, peppers, etc.) unless you have access to a greenhouse.

You can effectively add a few weeks to your growing season if you can start seeds inside under lights and then transplant them out into a cold frame, hoop house or other structure to protect and warm your plants. (I don't know your time, space or money budget for gardening.) A book on season extending, like "The Year-Round Vegetable Gardener: How to Grow Your Own Food 365 Days a Year, No Matter Where You Live" could be a big help. You may not have the resources to build the structures in the book, but the knowledge might still be helpful in figuring your own ways to adapt to a different climate.

I've also attached a link to an article about gardening in France, which describes some of the different climate patterns in France and has some links to some other gardening articles. Good luck!

Here is a link that might be useful: Vegetable Gardening in France

Thanks for all the advice. YOu also pushed me to think harder and I remembered I have met someone who has an allotment garden so I will also be asking her for advice. Best.

I was thinking snow peas, my favorite cool weather crop. :o)