There are too many variables for me to even begin to guess how to answer this. You have to keep records of how much you get per plant with the varieties you grow in your specific soil and with your specific growing condtions (I'd weigh them and keep track in pounds) per variety and calculate what you think would be enough from that data. To know how many tomatoes you need to harvest for canning, make a list of everything you want to end up with, in terms of a finished product. For me, the list most years includes salsa (including tons to give away), pasta sauce, pizza sauce, chili base, tomato sauce, stewed tomatoes, lots of regular sun-dried tomatoes, catsup and wine-marinated sun-dried tomatoes.

I've done it so long that I don't say "Okay, I need to make 26 jars of pasta sauce so we can eat pasta with home-canned sauce every other week".I am not that organized and our meal schedule is not that regimented. I just make whatever feels right that year.

After you figure out what you want to can and how much of each finished product you want to end up with, look at canning recipes and determine how many pounds of tomatoes you need in order to make however many pints or quarts you want of each end product. Calculate how many plants you think you need to meet that goal of x-number-of-pounds, and plant that many plants plus a cushion of 10% more plants to make up for any plants you might lose to pests, diseases, herbicide drift, etc. Then add a couple more plants just for fruit for fresh eating and fresh cooking.

I do not want to can tomatoes endlessly from May to November. I only want to can tomatoes in June and the first part of July. By mid-July, I'm through canning tomatoes, have yanked out the excess plants and kept just a few for fresh eating and for cooking fresh, and have planted something else where all those tomato plants once grew. I plant 100-120 plants every spring knowing that growing that many ensures we'll have a huge number of fruits available during the brief time frame that I want to can them.

I likely could be happy with 30-40 plants if I was willing to can more sporadically over a longer period, but I want to get my tomato canning done and move on to making pickles and canning peppers. Somewhere in there, I'm canning fruit as well. There is only so much I can do in a 24-hour day, so I have found the method that works best for me. You will have to find the method that works best for you.

There is a regular routine you get into if you are putting up food from each edible crop you grow. Luckily, our harvest is spread out over many months. I'd be crazy if I was trying to put up tomatoes, squash, okra, peppers, cucumbers, green beans and southern peas all at the very same time. I try to use my planting dates to stagger the harvest of various items so that I never have more harvest than I can handle. Most years, June is the worst because I'm still dealing with the harvest from the last of the cool-season crops while already dealing with processing the first big yields of the warm-season crops.

I do not know anyone who started out canning a year's worth of anything from their garden the first, or even the second or third year they began gardening and/or canning. There's a learning curve involved in canning just like there is in gardening. Most people I know who can now started out with just a batch or two of tomatoes and a batch or two of cucumbers or peppers that first year, and then grew more and processed more the next year, and then did even more the next year. It can take years to get to the point that you can figure out how to grow enough to can, freeze and dehydrate as much as you want to last a certain time period. And, we're assuming the weather cooperates, and you've lived here long enough now to know that the weather does not always cooperate with us.