Almost every time I teach a gardening basics course I get asked about crop rotation.
The question almost always goes something like this:
“Is crop rotation something I really need to do? It’s such a pain in the neck and my tomatoes are doing great where they are.”
I always answer YES crop rotation is super important and then explain why. Then someone else pipes up:
“But I’ve been planting my tomatoes in the same place for 10 years and I’ve never had a problem.”
To which I respond, good for you, your one of the lucky ones, but your days are numbered!!
Did you know that just like humans, vegetables have families? No, there is no such thing as brother, sister or even Great Aunt Millie tomatoes. Instead vegetable families are plants that have similar traits and if you went back far enough often a common ancestor.
Related plants also have very similar growing and nutritional needs. They use up the same nutrients in the soil and are susceptible to many of the same pests and diseases. So if you plant the same family of plants, in the same spot year after year, after year that spot will develop pest, disease and soil nutrition problems. You don’t have to look any farther than today’s big commercial mono-crop farm system to see what planting the same crop in the same spot every year can do to the soil.
There are a lot of different plant families in the home garden (8 major ones and a bunch of smaller ones). The point of this article is not to detail each family. If you would like a full list of vegetable plant families you can go to this post where I detail all the applicable veggie families.
Instead this post is meant to teach you the why’s and how’s of home garden crop rotation.
There are three reasons why we rotate our crops in our home garden, no matter how small the garden.
Those 3 reasons are:
- Nutrient use
The whys of crop rotation can be pretty complicated. I think the easiest way to explain why crop rotation is so important is to give you some examples of specific crops. I’m going to use 4 different crops to show you an example of why we do crop rotation. 1. Corn (Nutrient use) 2. Peas (Nutrient benefit) 3. Tomatoes (disease) 4. Spinach (Pests)
Example #1 – Corn Nutrient Use
First lets look at crop rotation of corn. Corn is in the Poaceae family. Corn has no other close relatives that we would normally grow in the home garden. In fact it is more closely related to your lawn than anything else in your garden. Corn is actually just a very large grass.
Corn is what we call a “heavy feeder”. This means that corn uses up a lot of nutrients in the soil, in particular nitrogen. So planting corn in the same spot for even 2 or 3 years, drastically depletes your soil nitrogen. Your soil needs time to recover from planting corn so you should rotate away for at least 3 years and take extra care to add back nitrogen to your soil after planting corn. Nitrogen can be replenished organically by adding compost to the soil, planting high nitrogen cover crops or even by adding grass clippings to the soil. Or even easier try Example #2!
Example #2 – Peas – Nutrient Benefit
Peas are in the Legume family. The Legume family also contains beans, clover and even peanuts.
The Legume family have very few problems and also have the amazing ability to be able to “fix nitrogen” from the air. This means that with the help of some special organisms in their root system they are able to add back nitrogen to the soil. So when you plant peas in a spot you can expect a nitrogen boost in the soil. Plants that follow peas will see the benefits of this added nitrogen. So you can rotate peas around your garden to help improve your soil.
Example #3 – Tomatoes (Diseases)
Tomatoes are part of the Solanace family which includes tomatoes, potatoes, peppers and egg plant. All of these plants are susceptible to many blight, bacterial and viral diseases.
Most of these diseases are soil borne. If you plant any of this veggie family in the same spot year after year you risk a build up of these diseases in your soil, which will infect new plants that you put in the area. Sound crop rotation principals tell us that we should rotate this family of plants out of the same spot for 3 or even 4 years!
Example #4 – Spinach (Pest Problem)
Spinach is part of the Amaranth family which includes spinach, beets and Swiss chard.
In our area all of this family are very susceptible to leaf miners. The adult version of this pesky bug lays eggs on the underside of the spinach leaves. The eggs hatch and the larva burrows inside the leaves of the plant destroying the leaf. Eventually the larva fall to the ground and hide in the soil. Next year they emerge as adults and start the process all over. Planting this family of veggies In the same spot year after year will cause such a build up of these pests and you will never get free of them, they can destroy a whole bed of spinach pretty quickly. So you need to rotate that crop, far from where it was planted last year.
There are just 4 of the many examples that can be given that show the importance of crop rotation.
Ideally it would be best to plant all one family in a bed and then not plant that same family in the same bed for at least 3 years. But even with a medium sized garden that can be a bit difficult.
I’ve worked out a 4 year crop rotation system that should work really well for just about any sized garden (even small ones). The last post in this crop rotation series will give you a quick breakdown of how this system works so that you can apply it to your garden as well.
Other Posts in this Crop Rotation Series:
1. Vegetable Crop Families
2. 4 year Crop rotation plan