As human beings, we tend to be creatures of habit. We fall into patterns and we have a tendency to stick with what appears to be working and not to change things. After all, if it ain’t broke, why fix it?
However, this modus operandi doesn’t always work so well with our gardens when it comes to where we plant our crops. If, for example, we’ve developed the habit of always planting our tomatoes in a row in the rear of our gardens and planting everything else in front, we may soon discover that these crops that have never failed us are starting to look more haggard and produce fewer fruits and vegetables. What’s going on here?
What’s going on is that your plants may have picked up a disease organism. Tomatoes, for example, are subject to blights, which, while they may not outright kill the plants, they will certainly reduce their yield. Brassicas (cabbage, broccoli, kale, etc.), meanwhile, can be susceptible to black rot, which will kill the plant.
So how to avoid this? The answer is to rotate your crops. Don’t always plant the same plants in the same place. If your tomatoes have been showing signs of blight, then next spring, plant them in a different part of the garden. If your brassicas died from black rot, then plant something else in their place (preferably something not susceptible to black rot). Be aware that black rot can survive in the soil for seven years, so you may have to plant your brassicas elsewhere for that amount of time or longer.
For a disease to gain a foothold and cause trouble, three things must be present. The disease organism, the proper conditions, and a susceptible plant. If you remove the susceptible plant from the spot (e.g. plant beans instead of cabbage in that location), then you remove one of the legs of this three-legged stool, and the disease (in this case, black rot) cannot infect your garden.
So, to paraphrase Pete Seeger, in every garden, you must turn, turn, turn!