Get the best out of your garden
You probably already know that farmers rotate their crops every year. This is to prevent their soil from becoming depleted and to ensure a productive harvest. Good gardeners will do the same thing and for similar reasons.
Some types of plants are heavy feeders. Others share similar diseases. Some plant families actually improve soil fertility. If you rotate your crops you can ensure that plants are getting the nutrients they need and are not sharing or spreading diseases. You will also decrease the pest population as over-wintering larva will not find their favorite vegetable nearby when they emerge in the spring.
Crop rotation is not at all complicated. You simply divide your crops into four families, and divide your garden space into four segments. Then every year you rotate the area you plant each family clockwise.
This chart illustrates.

The Four Families

Legumes and Leafy Crops
Legumes include peas and all varieties of beans (lima, green, dry, edamame, etc) This is the plant family that “fixes nitrogen” in the soil. That means that they are able to put more nitrogen into the soil than they take out. Since they enrich the soil, they are a great crop to plant just ahead of heavy feeders, like corn and the nightshades. Leafy vegetables are light feeders and quick growing and include lettuce, Swiss Chard, spinach and most herbs. Most of these plants are cold tolerant, so start planting this section first thing in the spring.
Fruiting
These include the heavy-feeding nightshades (tomatoes, potatoes*, peppers, eggplant and tomatillo) as well as all vining plants like cucumbers, summer and winter squash and melons. These are all cold-sensitive crops and they will be the last thing you put into your garden. Plant this crop once all danger of frost is past. Basil and tomatoes do well when planted near each other.


Brassicas
The brassicas include cabbage, cauliflower, Brussel sprouts, Broccoli, mustard greens and bok choi. These are cold tolerant plants. That means that not only can you plant them early in the season but they will continue to grow even after several frosts. They have thick, heavy root systems which means that they will loosen up the soil for the root crops that will follow in the next year. Dill is a good herb to plant among the brassicas.
Root Crops
These are all your under-ground veggies: carrots, onions, leeks, beets, turnips, etc. If you plan to store your surplus root harvest in cold storage (like a root cellar or cold basement), this will be the last crop you will harvest in the fall, probably after there have been several light frosts.
These crops do not do well in heavy soil. That’s why they do better when planted in the space previously occupied by brassicas. You’ll also want

to add plenty of organic matter like compost, chopped up leaves or peat moss to help loosen the soil. Pick out any rocks that might impede root growth.
Keep the families happy…
and you’ll have a happy and more productive garden.
Potatoes have the distinction of being the one root crop that belongs to the nightshade family. If you are having problems with blight, you should rotate your potatoes with the rest of the nightshades. If you have not seen any problems with blight or low potato production, go ahead and rotate them with the rest of your root crops.