In my post last week about crop rotation, I covered the very basics: moving plants from year to year helps preserve soil fertility and prevent pest problems. But as you might know, some plants are closely related to each other, and that complicates matters a little bit.

To help illustrate the related plants, I've adapted this list below from a great list at a University of Illinois Extension website:

Nightshade family: tomato, pepper, eggplant, potato, tomatillo
Onion family: onions, garlic, leek, shallot, chives
Squash family: cucumbers, muskmelon, watermelon, squash, pumpkin, gourd
Mustard family: cabbage, broccoli, cauliflower, Brussels sprouts, kohlrabi, turnip, radish, Chinese cabbage, kale, collards, mustard greens, rutabaga
Legume family: garden pea, snow peas, snap peas, sweet peas, snap beans, lima beans, soybean
Grass family: sweet corn, popcorn, ornamental corn
Carrot family: carrots, parsnip, parsley, celery, dill
Goosefoot family: beet, Swiss chard, spinach
Sunflower family: lettuce, Jerusalem artichoke, endive, salsify, sunflowers
Mint family: mint, basil, lemon balm, catnip

Now, how do you use this information? Well, the plants that are in the same family should be treated like a single type, in the sake of rotation. For instance, you might have this row order;

Year 1
Potato (Nightshade)
Cucumber (Squash)
Pumpkin (Squash)
Carrots (Carrot)
String beans (Legume)

For year two, instead of moving all the plants one row down, you'd want to take into account your two squashes - so move everyone two rows instead.

Year 2
Carrots (Carrot)
String beans (Legume)
Potato (Nightshade)
Cucumber (Squash)
Pumpkin (Squash)

Many gardeners don't plant in rows, but instead in blocks or even just zones. That's fine, too. In that case, to help you remember where you've placed things in the previous year, a garden journal is helpful. Otherwise, you might be staring into a lovely field of fresh soil in April saying, "Now was it last year that I had zucchini here, or two years ago? Hmm...."

Peas are one of my most favorite types of plants. They really thrive in the wet and cold spring of Montana, and then they tend to wilt when the heat of summer gets cooking (usually July) which conveniently allows sunlight to pass through the row and reach the summer heat-loving veggies that I plant near them. They do well in many other parts of the country, too - check with your local extension office for varieties.

In my garden, I plant all four of the basic types of peas - sweet, snow, snap, and shelling. Assuming you've got a good climate for peas (long, cool and wet spring), there are only three things you really need to figure out when it comes to peas. The first is what kind of pea you want (more on that in a sec). The second is whether or not your soil has the right microorganisms to grow peas, which is easily remedied if it is an issue. And the third is what you want the peas to climb. A wire fence that is at least 2 1/2 feet tall is best, but anything will do - a rock wall, some sticks and string, a trellis... the possibilities are endless. Peas are good climbers and will create a wall of vegetation along whatever they are able to climb.

Here are the types of peas:

• Sweet Peas: Gorgeous ornamentals and fantastic for cut flowers. The flowers come in all sorts of vivid and amazing colors, and last a long time once cut. These are a fun way to add nitrogen to the soil in a flower bed, while still producing a beautiful flower.


• Snow Peas: Thick podded peas that mature early, and you eat the whole darn thing. The peas itself is not nearly as important as the pod, which is almost string free and very succulent. So delicious!


• Snap Peas: Another thick podded pea that matures medium-to-early. Again, you eat the whole thing, but in this case your goal is a tasty pea in an edible pod. Some strings, but not a problem.


• Shelling Peas: A thin podded pea that matures later than the other kinds, with the goal being eating just the peas. The pods are thin and fibrous, and best to just compost (and not eat). This is the kind of pea you usually buy frozen in the store.

Now that you know your classes of peas, just select the type you want. For me, the Oregon Sugar Pod (a Snow Pea variety) is the proven winner. But I also grow Alaskas (Shelling) and Sugar Snaps (Snaps, of course). For Sweet Peas, just pick the color and height you want and go for it. I like the Royal Mixes myself, because the variety of colors lets me cut different tones of flowers to fill arrangements according to my mood. All red one week, lavender and pink the next!

Don't be intimidated by the microorganism thing. All legumes (peas, lentils, clover, and more) need certain tiny organisms living in the soil to thrive. The easiest thing to do to figure out if you soil is already colonized is to answer this question: Is there clover all around your yard and garden, perhaps driving you crazy? If so, you're set. Now, if you are thinking, "Well, I have a little clover here, and a little there... but it isn't everywhere," then you need to go to step two: Clover inspection.

Dig up a clover plant and shake all the dirt off the roots. Are there lots of weird little buttony-knobby things sprinkled around the roots? These are the little houses for the microorganisms that legumes need to thrive. If you clover has them, your peas will have them. It won't hurt you to skip the step of inoculating the peas, in this case.

Now... if you have no clover, or if you are starting from all imported fresh soil, or if you just want to hedge your bets, you'll need some "inoculant." It is usually a powder that you sprinkle on the soil, as you plant the peas, to help them grow. It is available as an organic product. Personally, I have never inoculated my peas because I have clover growing out of every nook and cranny of my entire property. But if you are in doubt, it might really help your peas out. Some people swear by it.

There are two primary benefits to crop rotation, and they apply to the smallest of backyard farmers as much as to huge agro-conglomerates.

The first is based on the fact that all plants are prone to certain pest issues. For some it is a specific insect, while others are likely to get fungal infections. To prevent these issues from becoming overwhelming, one of the best tools of smart and chemical-free gardening is to put a given type of plant in a new place every year, as space allows. The idea is that any pest specific to your plant that is living in the soil from last year won't be able to find the plant in its new home. This is a great way to keep blemishes and worms off of root vegetables, minimize leaf miners, and generally keep the pests populations low for any kind of plant.

The second is the fact that each plant needs, depletes, and sometimes adds, a different combination of nutrients from the soil. Some plants, like peas, beans, and clover, will add nitrogen. Others, like carrots, tend to strip nitrogen out of the soil really quickly. As a result, you can accidentally create nutrient-poor zones if you keep planting something in the same spot.


Orderly rows make crop rotations easier

So how does a regular backyard gardener take this into account? The most basic part is simple: Plant each zone with a different plant than last year, and try to do it in an orderly fashion so that you can remember what you did. So, for instance, if you imagine each bullet below is a garden row,

if year one's rows are organized:

• carrots


• peas


• tomatoes


• onion


• potatoes

Then year two should go:

• potatoes


• carrots


• peas


• tomatoes


• onion

And year three:

• onion


• potatoes


• carrots


• peas


• tomatoes

There are some tricks here, like the fact that potatoes and tomatoes are biologically similar, so it helps if you don't make them direct neighbors. And the carrots are always marching behind the peas, which helps with soil nutrition. But really, the most important thing is to keep your plants on the move throughout the years. Even if you just grow two things in a single swath of dirt, switch them from side to side each year.

In another post, I'll delve a tiny bit into plant families, which will help the more adventurous gardeners plan a better crop rotation scheme. For most backyard veggie gardeners, though, just a one-year row shifting scheme as written above will do the trick.