As you've seen in previous years, I map out my garden beds each year in an Excel spreadsheet. It's probably not the best program for this purpose, but it's handy, since it's what I already use for keeping track of the planting schedule. If you look at the garden maps I made for 2013 and 2014, you'll see that instead of keeping the same basic layout from year to year, I move my crops around as best I can in the limited space available. Rotating crops is a standard gardening trick for fighting pests and disease; if critters or bacteria are left behind in the soil from one year's plants, they won't find anything suitable to prey on in the same spot next year. It can also be helpful for plant nutrition, since some plants (like tomatoes), are "heavy feeders," while others (like peas and beans) actually add nitrogen to the soil. So I like, when possible, to plant my tomatoes in the spot where I had peas last year, so they'll have plenty of good soil to feed on.
Unfortunately, when I first started rotating my crops, I didn't really plan for the long term. I just made sure that the peas and tomatoes each went into a different spot from where they'd been the previous year. This means that for the past four years, the tomatoes have been progressing clockwise from trellis to trellis around the garden, while the peas have been moving in the opposite direction. Logically, it would make sense for them both to move in the same direction, so that the tomatoes would always move into the spot just vacated by the peas. But because I didn't start out doing it that way, I can't just start doing it now; that would mean putting this year's tomatoes in the same spot where they were two years ago, which would leave them vulnerable to disease. So basically, the only spot where I can safely put the tomatoes is in the back right corner.
The zucchinis pose a similar problem, and on a bigger scale. Each plant takes up three square feet of garden space, and because they like a lot of sunlight, the only really good spot for them is at the southern end of the garden. Unfortunately, keeping them there all the time would make them easy prey for the squash vine borers and the powdery mildew that caused such a lot of trouble for us last year. So those two plants pretty much have to go in the only two corners that haven't hosted them for the last four years.
These constraints make the process of putting the garden beds together a bit like doing a jigsaw puzzle. The tomatoes and zucchini are like the corner pieces, fixed in place, and everything else has to fit in around them. Let's see, cucumbers over here...beans near the cucumbers, which is supposed to be a beneficial combination, and basil near the tomatoes for the same reason...fit the individual squares in around the big blocks...and you end up with something a bit like this.
I'm hoping that in future, I can manage to get everything arranged so that I can just rotate whole beds instead of trying to piece all the crops together one by one. It'll be a lot less work that way. But I'll have to wait at least one more year to get the zucchini rotated into a reasonable spot.
For now, though, I'll consider it enough of a triumph to have a workable plan for this year. In the middle of February's frozen wasteland, I can look on this garden map—and my first batch of seedlings—as tangible evidence that, no matter how frigid it feels right now, spring is definitely on the way.