Round and Round in the Garden with Crop Rotation

By Susan Littlefield

Winter is a great time for garden planning. And one of the things to always keep in mind when sketching out ideas for the upcoming season's vegetable garden is where in your plot the crops you grew last year were cultivated. Keeping track of this information allows you to put your crops in a new spot in the coming year. Even if your garden is small, it's a good idea to rotate the location of your vegetables within your garden plot for several reasons. Locating a particular crop and its relatives from the same family grouping in a new spot each season will reduce insect and disease problems and optimize use of nutrients, giving you the best results for your efforts come harvest time.

Good Reasons for Rotating Crops

Some pests and diseases can carry over in the soil; switching the spots where particular crops are grown can help foil their attacks. For example, all members of the cabbage family are susceptible to many of the same fungal diseases. The spores that spread these diseases can survive in the soil, often for several years. So making sure to plant your broccoli, cabbage, kale, and other cole crops in a new spot for at least three years reduces the likelihood that your plants will become infected. The spores that cause the fungal disease early blight on tomatoes can survive in the soil for at least a year. Setting out tomatoes in a new location will help you grow a healthier crop.

Different plants take different amounts of nutrients from the soil. Leafy greens like spinach need lots of nitrogen, while legumes like peas and beans actually add nitrogen. Members of the squash clan, including cucumbers, melons and pumpkins, have a higher phosphorus requirement than tomatoes, eggplants and peppers.

Rotating crops can also help to keep soil in good tilth. If shallow-rooted crops like cabbage are followed by deeper rooted crops like tomatoes, soil compaction can be lessened. The repeated hilling of the soil needed for corn and potatoes helps to reduce the number of annual weeds in that section of the garden.

Here's just a sampling of the many great varieties of vegetable seeds we offer, representing the common plant families found in the vegetable garden.

'Scarlet Nantes' Carrot (68 days) — It's no surprise that these sweet-tasting, 6-inch long, blunt tipped orange root vegetables are in the Carrot Family.

'Golden Sunrise' Swiss Chard (53-59 days) — This Goosefoot Family member has beautiful golden stalks, midribs, and veins, as well as tender, succulent leaves.

'Fanfare' Cucumber (62 days) —This Gourd Family member produces dark green, slim, flavorful cucumbers on compact, disease-tolerant vines over a long period.

'Ambrosia-SE' Sweet Corn (75 days) —A bicolor with superb eating quality, this Grass Family member has early vigor and tolerance to Stewart's wilt.

Sweet Basil — Perfect for seasoning tomato dishes or making pesto, this Mint Family member has shiny green leaves.

'Packman' Broccoli (50-52 days) — An early variety that produces a dark green central head quickly and harvestable side shoots after the head is cut, this broccoli is a member of the large Mustard Family.

'American Flag' Leek (120-155 days) — This cold tolerant member of the Onion Family produces long, thick white stalks with a yellow heart.

Putting Together a Rotation Plan

So how do you put all this together into a plan? First of all, it may not be possible to have an ″ideal″ rotation plan in a small backyard garden -- just do the best you can. If you can only site your tomatoes in a new location for two years rather than three, that's better than setting them in the same spot year after year.

The first step is to group the plants you plan to grow into families with similar pest problems and nutritional needs. Here are some common family relations to help you plan your moves.

Carrot family (Apiacea): carrots, celery, chervil, cilantro, dill, fennel, parsley, parsnip

Goosefoot family (Chenopodiaceae): beets, chard, spinach

Gourd or Squash family (Cucurbitaceae): cucumbers, melons, squash, pumpkins

Grass family (Poaceae): corn

Mint family (Lamiaceae): basil, mint

Mustard or Cabbage family (Brassicaceae): broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, radishes, rutabagas, turnips

Onion family (Alliaceae): garlic, leek, onion, shallot

Nightshade or Tomato family (Solanaceae): eggplant, peppers, potatoes, tomatoes

Pea or Legume family (Fabaceae): beans, pea

Sunflower or Aster family (Asteraceae): artichoke, cardoon, chicory, endive, lettuce

Then come up with a plan that will move these groups through the garden according to their nutrient demands listed above. One plan might be to start with legumes like peas and beans to build up the soil. Follow this the next year with leafy greens and cole crops to take advantage of the increased nitrogen in the soil. Then come fruiting crops like the squash and tomato families that will thrive with a little less nitrogen. The fourth season, finish up with root crops and onion family members with their relatively low fertility needs. Then it's back again to peas and beans.

So get out the graph paper and have some fun sketching out possible plans now. Then, when spring comes, you'll be ready to move your best plan from paper to garden plot.

Question of the Month: Growing Kohlrabi

Q: A friend of mine grew a strange looking vegetable called kohlrabi in his garden this fall. He gave me one to try and it was delicious! What's the best way to grow this unusual vegetable?

A: Kohlrabi is indeed one of the oddest looking vegetables you can grow. With its large, edible, bulbous stem sitting underneath big, cabbage-like leaves, it almost looks like some alien spacecraft that landed by accident in the middle of the vegetable garden! But the enlarged stem of this cabbage family member- its name means ″cabbage turnip″ in German- has a sweet, mild flavor that has been likened to a cross between a radish and a cucumber. It can be enjoyed crisp and raw, steamed, stir-fried, or added to soups and stews. And even the leaves are edible- you cook them as you would kale.

This fast-growing vegetable does best when the weather is cool. It can be grown as a spring crop and also makes a good fall crop in many parts of the country. In the spring, sow seeds outdoors 4-6 weeks before the last frost date and make repeat sowings every week or two while the weather remains cool. For a fall crop, sow seeds directly in the garden 8 to 10 weeks before the first expected fall frost date. In warm winter areas (Zones 9 and 10), you can make repeat sowings during the fall for harvest in the winter and early spring. Plant in wide rows or beds, spacing the seeds 3 inches apart. After the seedlings are a couple of inches tall, thin to a final spacing of 6 to 8 inches.

Plant in full sun in soil that has been enriched with compost or other organic material, and be sure to keep the soil consistently moist; mulching is helpful. Your kohlrabi plants will appreciate a dose of fish emulsion fertilizer when they are about a month old. Floating row covers will keep away many of the pests that trouble members of the cabbage family, such as cabbage loopers and cabbageworms.

The best advice about harvesting kohlrabi is not to wait too long. Most varieties are ready for harvesting just 6 to 7 weeks from planting and are the most tender and flavorful when the bulbs are 2 to 4 inches in diameter. Fall crops that ripen in cool weather don't get woody as readily and can be picked at little larger size, up to 5 inches across.

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