When planning crop rotation in the home garden, you need to know the family ties of your veggies and herbs. Illus.: Claire Tourigny
Crop rotation is an age-old cultural practice that involves never growing the same vegetable, or even a vegetable from the same plant family, in the same place two years in a row as a means of reducing disease and insect infestations.
For example, always growing tomatoes in the same spot year after year would be looking for trouble. That’s because most tomato disease spores (and tomato are just about the most disease-prone vegetables, aren’t they?) overwinter in the soil at the base of their host plant. When you replant tomatoes in the same place the following year, the disease is already there, ready to attack. But if you plant your tomatoes elsewhere, the spores will not be able to easily reach them. And that’s the basis of crop rotation.
So, rotating your tomatoes is a great start, but since peppers are from the same family as tomatoes (Solanaceae) and are prone to many of the same diseases, peppers should not be planted in that spot either. Nor should eggplants, nor ground cherries, also in the Solanaceae family.
The same goes for all other vegetables. Try to rotate your vegetables not just by species, but by family.
The same applies to insects: most overwinter, as eggs, pupae or larvae, at the foot of their preferred host. Except … insects are more mobile than spores. If they can’t find their preferred host nearby, they’ll go looking for it. This is doubly true if they overwinter as pupae, as they give rise to winged adults right away. At least overwintering eggs give larvae that are not as mobile.
Better yet when it comes to insect control, crop rotation can be combined with the use of an insect barrier, such as floating row cover, and thus conquer even flying insects. You plant the vegetable in a new spot where there are no eggs, pupae or larvae, cover it with an appropriate barrier and how could the insect get to it? (Read The Perfect Insect Barrier! to better understand how this works.) A simple two-year rotation can suffice in such a case: an insect that doesn’t find its host one year will die out and won’t leave any offspring for the following year!
In an ideal world, you’d stick to a 4-year crop rotation for the vast majority of vegetables, especially because of longevity of diseases, as some spores can survive dormant in the soil for several years. However, it isn’t easy to carry out a 4-year rotation in a small home vegetable plot where plants are all planted in very close association. So, if you’re stuck, even a 2-year crop rotation is better than none!
No Need to Rotate Permanent Vegetables
Not all vegetables need to be rotated. Rhubarb and asparagus, for example, are not grown like other vegetables. Unlike tomatoes and beans that you start from seed every year and can easily rotate, they’re permanent (or at least live decades). So, just plant them and leave them be.
Vegetables Classed by Plant Family
To help you plan crop rotation in your vegetable garden, here is a list of the main plants grown in temperate climate vegetable gardens (i.e., vegetables, herbs and certain small fruits) classified according to their botanical family.
New Zealand spinach
Amaranthaceae (including Chenopodiaceae)
Convolvulaceae (Morning Glory Family)
Lamiaceae (Mint Family)
Rosaceae (Rose Family)