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My garden has clay type soil. What is the best way to improve the soil?

One agriculture professor told me adding sand to clay is like putting beach balls into a room full of oatmeal for aeration. It only makes cement, unless you use an awful lot of sand.

What is a good way to control weeds in a garden?

Why Garden Organically?

Since the "organic law" does not apply to home gardens, why would any gardener give up all synthetic fertilizers? And why not use synthetic pesticides, when just one application could eliminate even the most devastating ravages of a crop insect or disease? Why work so hard handling large quantities of organic soil amendments and manures, when synthetic fertilizers of every description and purpose are so quickly available and easy to use?

Early gardeners did it to preserve a way of life that reduced pollution and environmental decay, thus creating a more ecological society. Organic enthusiasts are extremely health-conscious, and hope that working vigorously outdoors and eating foods free from pesticides just might lead to better nutrition and health. Today's organic gardeners are even more ecologically aware due to the accelerated deterioration of the environment from all forms of man-made intrusions. They can see waste-disposal sites filling up due to an ever-increasing population and proliferation of technological litter. Organic wastes must go somewhere, and organic gardeners see the soil and its capacity to recycle as the best place for them.

Today's organic followers include not only purists but also individuals who see it as their small contribution to conserving resources and energy. It's their way of rebelling against the passage of the agrarian way of life and the arrival of chemical agriculture that is now necessary to feed a population increasing at alarming rates. Rather than ignoring this preference, the scientific community is increasing its efforts to reduce the need for chemicals.

Companion planting

Companion planting may be defined as the interplanting of two or more crops which benefit from being near each other. Some of the benefits of this technique are:

  1. Control of insects
  2. Improvement of soil structure
  3. Control of weeds
  4. Thinning of crops
  5. Improvement of crop products.

Scientifically, very little is known about companion planting. Some gardeners testify that it works for them, but others view companion planting as unfounded and wishful thinking. Each of the benefits mentioned above has some substantiated scientific basis, however. The effectiveness of other plants, such as aromatic herbs, which are supposed to repulse insects with the aroma they release, is less certain.


Insect Control. Insects may be repelled, attracted, or killed by some plants. For example, interplanting marigolds with crops may control nematodes in the soil. Catnip is reported to deter flea beetles. Mints, rosemary, sage, rue, and tomato are said to drive away white cabbage moths (looper adults). Garlic, by some accounts, repels Japanese beetles. You may want to use some trial-and-error approaches to determine the effectiveness of aromatic plants in repelling insects. Do not assume that the insect resistance of one plant will be imparted to another species growing nearby.

Some plants may attract predatory insects into the garden. Fennel may increase the population of wasps in the garden which control larval stages of insects, such as Mexican bean beetles, hornworms, and cabbage maggots, and supposedly some adult insects. Asters attract spiders which may feed on some garden pests. Diversity of planting may foil insects. Interplanting beans and potatoes is often suggested, but results have been varied.

Some plants may act as traps, attracting the insects to them rather than to the principal crop. Some examples which have been suggested are planting eggplants with potatoes to attract the Colorado potato beetle, planting tomatoes with corn to attract corn earworm (tomato fruit worm, tomato bud worm) or vice versa, and planting turnips, radish, or mustard to attract the Harlequin bug from other crops.

Improvement of Soil Structure. Some plants, such as alfalfa, parsnip, caraway, and tomato, are deep-rooted crops which penetrate the soil and may help break up compact subsoils and pans and help loosen and crumble the upper soil levels. Other crops do not benefit directly at the time a deep-rooted crop is growing in one site, but if you rotate crops, the next crop may benefit from the improved soil structure.

Control of Weeds. The science of controlling weeds by crops is in its infancy. Some plants have toxic effects on others. Walnut wilt is a disease of tomatoes growing underneath walnut trees. Walnuts exude a chemical which is toxic to many plants. Crop residues may release toxic residues which control weeds. The effectiveness of the control is usually limited. Marigold residue may be worth a try in weed control.

Improvement in Product. This factor is most noticeable in crops harvested as forages (hay, silage) where the interplanted species are removed together. Grass-legume mixtures are common interplantings. The grass provides carbohydrates and fiber to the forage, and the legume provides protein to enrich its quality. Interplanting soybeans with corn is possible. Alfalfa/bromegrass mixtures are well-recommended. It is unlikely you can enhance the flavor of vegetables by planting them close to herbs.

Thinning of Crops. Interseeding a crop with one which matures sooner can give a properly thinned stand of the later-maturing crop. Carrots and beets or radish may be seeded together. When the radishes or beets, as greens, are harvested, it leaves the thinned carrot stand behind. On the other hand, carrots and leeks may be interseeded. The leeks occupy space so that the carrots are not too thick. The carrots are the first to be harvested.


As with many practices, companion planting does not work for everyone or every time. Unsubstantiated testimonials are often the basis for companion planting. Caution is needed with claims such as "carrots dislike dill," "plant parsley with roses to repel beetles," "interplant asparagus with tomatoes and parsley for mutual benefit."

In addition, failure to recognize the true beneficial factor may lead to false impressions. People who state that the best melons or pumpkins come from the weediest parts of the patch are probably overlooking the fact that a very fertile soil is stimulating weed growth and crop growth relative to less fertile areas. The failure to control weeds in a garden normally leads to reduced yields relative to the full potential of the soil to produce a crop. It is more likely that better melons or pumpkins would have been harvested from those weedy spots if the weeds had been controlled. Weeds compete with crops for light, water, and nutrients and harbor diseases and insect pests.

Selecting Companion Plants

You should apply common sense and science to selecting crops for interplantings. Consider the relative competitive nature of the crops. Competition may be evened out by crop spacing, however. Be sure that a larger or more aggressive crop does not shade out a smaller crop. Deep-rooted crops may not be good companions for shallow-rooted crops as is often recommended. The deep-rooted crop may exhaust water from the lower strata of the soil leaving the shallow-rooted crop high and dry. Published articles, suggestions from other gardeners, and trial and error can lead to successful selection of interplantings. Scientifically-based knowledge about companion planting is scarce.

Designs for companion plantings

Plants in intercropped systems may be placed in several arrangements. Some designs may be best suited for certain crops. Each plan must be well-developed; otherwise, one or both crops may fail.

Interplanting in the Same Row. This design works well for plants of about the same size and with similar growth habits. They should grow at about the same rate, particularly until one of the crops may be harvested. Example: beets and radishes work well in this system.

Zig-zagged Rows. This arrangement allows for a group of plants to be tucked into another group of plants. Plants of dissimilar size and growth habit may be used. Example: beets and onions work well in this system.

Sections. Rows of crops may be planted between the rows of other crops. Variable spacing of rows may be used to allow light to reach each crop. Plants may be grouped together for a better appearing garden. Example: corn and pole beans work well in this system.

Borders. Borders may be used around other plantings for a variety of reasons. You may want to test the repulsive action of herbs on pests. Annual planting may be made with a perennial border or around a central planting of perennials. Attractive gardens may be made with borders. Try planting a rhubarb border around annual vegetables or have an asparagus bed surrounded by tomatoes or other annual vegetables.

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This page was last updated on January 23, 2006