Companion Planting, Crop Rotation, and Weeds

Weeds are people's idea, not nature's.

Author unknown

But while his men were sleeping, his enemy came and sowed tares (weeds) among the wheat, and went away.

New American Standard Bible, 1955

It is a basic understanding of organic and biodynamic gardening that nature functions as an interacting whole. Every part has an effect on every other part. Why should plants growing next to each other in the garden bed not follow this principle? Many gardeners have observed such mutual influences. Scientists have been slow to study these effects because the current scientific methodology has great difficulty isolating and locating the exact interactions and the semiochemicals (pheromones, allo-mones, kairomones, repellents, and attractants) involved. As we have seen, a similar problem exists in the study of lunar and planetary influences on plants; it is nearly impossible to separate the significant from the insignificant variables and to repeat the exact conditions in experimental settings.

Nonetheless, few scientists deny such interrelationships among plants, and a fledgling field of synecology, plant sociology, and allelochemics (the study of the effects of plant excretions on one another) exists. Pfeiffer has mentioned research done in the 1930s. Helen Philbrick and Richard B. Gregg undertook a pioneer effort on the subject in a book called Companion Plants and How to Use Them. It is admittedly a primer and not a scientific treatise, but it is useful for gardeners since it lists all the entries in alphabetical order. Louise Riotte wrote a similar book called Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening.

What are the reasons for companion plant effects? Different species are accumulators of different substances that are vital within the whole ecology. We all know how legumes function as accumulators of nitrogen, creating beneficial effects for plants growing beside them or following them in rotation. Other plants have other functions within the organic totality. For example, daisies, broom, buckwheat, dandelion, and chamomile accumulate calcium, even if growing in calcium-poor soil. Henbane, thorn apple, and valerian specialize in phosphoric acid. Foxglove collects Fe, Ca, Si, and Mg. German chamomile collects K and Ca; horsetail is an avid collector of Si; yarrow collects K, Ca, and Si. The list goes on indefinitely. Measurements are hard to specify because some plants increase the percentage of elements with age as the plant grows, other decrease the percentage. Hauschka indicates rhythmical variation during the year and during the lunar cycles. Conditions of the soil substrate influence the chemistry of plants, so that, for example, tobacco is rich in K when it is grown in soil poor in K and vice versa. Furthermore, the study is complicated by suggestions of elemental transmutations as researched by Kervran, Hauschka, and Spindler.

Plants are not passively at the mercy of their environment, but actively engaged in selecting and rejecting nutrients, sending root hairs throughout the soil and then dying back, altering the soil in the process and providing specific conditions for the myriad of microorganisms, which in turn alter the chemistry of the soil. These biological processes make use of mechanical laws such as diffusion, osmosis, and so forth, but much of it occurs contrary to purely mechanistic laws, just as plant growth itself counters the law of gravity. As the great Dutch botanist Hugo de Vries pointed out in 1905, the chemical combination of the plant does not conform to that of the soil or water in which it grows, and sometimes the variation in two adjacent plants is very great.

Not just the elements are accumulated and given off by specific plants, but also the complex compounds such as amino acids, hormones, enzymes, auxins, growth inhibitors, and others, not all of which have as yet been discovered. These biotic substances are given off into the surroundings of the plant as the perfume or pollen of the flowers, as essential oils by the leaves, by excretions of the roots, by the discarding of dying plant tissue, and they are carried in insect droppings or by insect go-betweens, as is the pollen by the bees. Sometimes the quantities given off are minute, occurring in homeopathic dosage or at the rate of trace minerals. A few years ago, such incredibly small quantities would have been scorned as ineffective, but now it is known that some elements, even when removed to a distance, have an effect on the living organism of a plant. Plants, especially herbs, as they give off minute substances that alter soil flora and other plants, work within the ecology of the soil much like the endocrine glands within the microcosm of the animal organism, by regulating metabolism, reproduction, and other life functions by minute chemical programmers. Since we are dealing with a macrocosmic process, the effects are not as compact as they would be in a more specialized organism. The companion effect can be created by purposeful planting of certain species next to each other, or sometimes by the administration of herb teas and ferments to the soil. Companion plant effects are probably more widespread than we realize. One need only look at fields, meadows, and forests to realize that some species prefer to grow with specific others, fitting together like the pieces of a jigsaw puzzle. Up until the dawn of ecological studies, our biological science labored under the assumption that the first law in nature is the struggle for survival and the survival of the fittest. We have seen that this dog-eat-dog idea is more a projection of the conditions created by industrialization and class struggle than a true understanding of biology. Why should plants not have evolved for mutual benefit? As the conservationist Joseph Cocannouer shows so effectively, even weeds, having evolved right along with horticultural practices, often have beneficial companion effects; they are not just mean competitors for nutrients.

Flowers make good companion plants, also, besides adding beauty to the vegetable garden. The suggestion has been made that flower saps keep predators alive when pests are in low supply. The predators of sugar-sap-secreting aphids are kept around the garden by having flower nectars available. Borders of aromatic herbs keep hungry insects away from crop plants, possibly because the fragrance masks the odor of the other plants. Other companion plants distract the insects from the crops.

As Alan Chadwick points out, concerning the effects and influences of plants upon one another, here, too, it is the craft of the gardener to create relationships and dis-relationships by planting some plants together and avoiding others.

Many native horticulturists have been aware of companion planting and have incorporated it into their agricultural lore. King reports examples of multiple crops in the Far East, such as wheat, Windsor beans, and cotton, or alternating rows of beans and millet. Other examples are cited in ethnographic accounts, but much more research could be done in this area. Famous are the combinations of the American Indian companion cropping of corn, beans, squash, often with amaranth and a number of weeds that served as soup greens. The anthropologist Clifford Geertz tells of the almost uncanny imitation of the natural ecosystem of many slash-and-burn horticulturalists: The swidden plot is not a field at all in the proper sense, but a miniaturized tropical forest composed mainly of food producing and other cultivates. Anthropologist Roy Rappaport writes about the Tsem-baga of New Guinea. He reports that the use of companion and successive planting results in maximum utilization of the sun's energy by the leaves, protection of soil against washing out even on hillsides, discouragement of insects, and the availability of alternative food supply if one crop does not yield. The jungle-like atmosphere is recreated when he writes: A mat of sweet potato leaves covers the soil at ground level. The taro leaves project over this mat; the hibiscus, sugarcane and pitpit stand higher still, and the fronds of the banana spread out above the rest.

As a final example of interplanted gardens, we read the description of a typical Guatemalan garden as seen by a botanist:

The garden I charted was a small affair about the size of a small city lot in the United States. It was covered with a riotous growth so luxuriant and so apparently planless that any ordinary American or European visitor accustomed to the puritanical primness of north European gardens, would have supposed (if he even chanced to realize that it was indeed a garden) that it must be a deserted one. Yet when I went through it carefully I could find no plants, which were not useful to the owner in one way or another. There were no noxious weeds; the return per man-hour of effort was apparently high.[...]

He goes on to describe the great variety of plants complete with fruit trees, shrubs, flowers, vegetables, and beehives, stating that though it was on a slope, there was no problem of erosion because of the intertangled root systems; pests and diseases were checked because individuals of the same plant species were separated by other plants; and there was high efficiency in terms of production per pound of vegetables and fruits per man-hour per square foot. In terms of American or European equivalents the garden was a vegetable garden, a medical garden, a dump heap, a compost heap, and a bee yard.

The biodynamic, French intensive method of gardening as taught by Alan Chadwick has reintroduced such high energy gardening into the temperate latitudes.

Since other books have been written on the subject, only a partial listing of companions is made here. These were gathered by observant gardeners and gleaned from tradition.

A Few Good Companion Plant Combinations

Beans grow well with almost everything, especially cucumbers, strawberries, early potatoes, cabbage, and celery.

Cabbage grows well with bush beans, is aided by border plantings of dill and chamomile, and when interplanted with hemp (Cannabis sativa), it has less problems with the cabbage moth. Fall cabbage will do well when preceded by early potatoes.

Celery and any member of the umbellifer family, such as carrots, parsnips, Hamburg parsley, and celeriac, will grow well with any member of the lily family, such as onion, shallots, garlic, and leeks.

Carrots and leeks grown together will discourage carrot fly and onion fly. Carrots are good to grow after flax, which loosens the soil. A combination of onion, lettuce, and carrot makes an excellent early bed.

Corn combines well with beans, squash, and cucumbers.

Cucumbers grow well with corn and lettuce.

Herbs make good companions for all vegetables. Stinging nettle increases the volatile oils of mints.

Kohlrabi grows well with beets and onions.

Leek grows best with celeriac or celery because both like potash fertilizer and require the same amount of care. Wood ashes, composted pig manure, or a mulch of bracken fern provide K.

Lettuce does well when interplanted with carrots, radishes, strawberries, or cucumbers.

Onions are good with beets, lettuce, beans, and any member of the carrot family.

Peas grow well with radishes, carrots, cucumbers, spinach, and turnips.

Potatoes benefit from beans, cabbage, and peas. A border of horseradish and hemp is beneficial for them.

Radish likes nasturtium, chervil, and peas.

Spinach grows well with strawberries.

Swiss chard can be interplanted with cabbage and endives.

Tomatoes like New Zealand spinach, parsley, and basil as a ground cover. They also grow well near a row of asparagus.

Turnips grow well with peas.

Some plants do not make good companions. The vegetable Florence fennel is unsocial and likes to have the bed all for itself, although I have grown good carrots among the fennel. Carrots do not like dill. Onions do not go well with peas and beans. Potatoes become stunted when sunflowers or Jerusalem artichokes are grown with them, and they do not like cucumbers.

Surprisingly enough, often what tastes good together when cooked into a meal also makes for good companion planting. For example, good food or planting combinations are beans and savory; beets and onions; cabbage and dill; carrots and leeks; corn and beans (succotash) or peas; tomatoes and parsley or basil; lettuce with carrots, onions, and radishes; horseradish and potatoes. Of course, this rule, like so many other rules in gardening, cannot be absolutized.

Intercropping

Intercropping is similar to companion planting in that several species are planted into the same bed, but the purpose is less that of mutual symbiotic effects than that of maximum utilization of garden space. A main crop, such as cabbage, bush beans, squash, etc. that takes a long time to mature is interplanted with quick-growing, quick-maturing crops, such as loose-leaf lettuce, kohlrabi, radishes, garden cress, or spinach. The secondary crop will be harvested before the main crops spread out to fill the space, or they are hoed into the ground as green manure. Another kind of intercropping is practiced when a tall growing crop is grown with a low, crawling plant that will provide ground cover, or living mulch. For example, cucumbers can be grown among corn, New Zealand spinach or nasturtiums under tomatoes, or squash under pole beans.

The staggering of crops refers to sowing or planting the same species at different times of the year, such as lettuce, peas, or radishes, which can be sown out every month before it gets too hot. This can be worked into a system of intercropping and companion planting.

The gardener must keep good records in his or her diary of each of these sowings, in order to work out the best combinations and rotations for one's particular situation.

Crop Rotation

Just as companion planting is in keeping with the natural plant associations, so crop rotation makes use of the principle of natural plant succession. A landslide or a freshly bulldozed plot will quickly be settled by fleabane, nightshade, docks, mulleins, Queen Anne's lace, and other annual and biennial pioneer plants. They are first-aid plants, holding the soil and keeping it from being washed or blown away, working much like scar tissue on a body. Next in the succession are the tightly matted thorns and brambles guarding the ground, warning us, Sorry, you can not go through here now, but, here, don't be angry, have some berries! Amidst the shade and protection of the brambles, trees make a start, quick-growers like willows and cottonwoods, or, in drier areas, Manzanita and sugar pine. Many decades later the climax forest reestablishes itself if nature is left to itself. Such is a natural succession as one might find in Oregon.

In the garden the induced succession is not as elaborate but it, too, follows its own natural laws involving crops and weeds. Abundance of nasty weeds, or of a singular species of weed, tells us that the soil has been treated one-sidedly. Weeds are a sign that the earth wants a change to redress whatever imbalance there is in the soil. Lamb's quarters will take over land that is tired of potatoes, for instance. A season of weeds makes a good fallow to restore balance, a practice made use of in the three-field system of the Middle Ages.

There are several rotational plans that may be followed by the gardener. One is to identify the heavy feeders, consisting mainly of leaf crops (i.e., cabbage, lettuce, Swiss chard, spinach, celery, leeks, corn, cucumbers, squash, and nightshades such as tomatoes, eggplant, peppers); the soil improvers, consisting of nitrogen-fixing legumes (peas, beans, broad, or fava beans); and the light feeders, consisting mainly of root crops (carrots, beets, parsnips, Hamburg parsley, rutabaga, turnips, onions, Jerusalem artichokes). The rotational cycle starts with heavy feeders planted in freshly fertilized soil (compost in Stage II or III). After they are harvested the soil is given a rest with a leguminous crop, which fiberizes the soil and restores some of the nitrogen. Then the light feeders may be sown in, with a dressing of very ripe compost (Stage III), to complete the cycle. A weed fallow, or a crop of completely unrelated plants such as a bee pasture of scorpion weed (phacelia), flax, or buckwheat, which are not ordinarily in the rotation, may follow; or the cycle can be started again immediately.

Another plan of rotation is similar but starts from different considerations. In order that the entire four-fold plant finds expression in the garden so that the four ethers are harmoniously balanced, one should plant root, leaf, flower, and fruit-seed crops. A bed starts out in the first season with leaf crops which are mainly heavy feeders, followed by flowers, which are beautiful and easy on the soil, followed by seed and fruit crops, including legumes, and, finally, in the fourth season, followed by root crops, which include most of the light feeders. In essence this method is not much different from the first one mentioned, though it may be easier to remember.

One more consideration enters the planning of functional rotations. One must know the plant families to which the crops belong, so that members of the same family are not planted on top of one another. Family members tend to have the same nutritional needs and would wear the soil one-sidedly if planted in succession. It is surprising that out of the many thousands of plant families, only a mere dozen or so have chosen to let themselves be cultivated.

Weeds

Like the insects, weeds have caused a lot of thoughtless reactions—providing targets, for instance, for misplaced fixations about cleanliness. Some gardeners are fanatic about keeping weeds out of the garden, as though they were dread enemies and use strong herbicides that not only wreck the garden ecology, but prove to be adverse to human health as well. This paranoid attitude even finds its way into the literature where, for instance, it is written of the sheep sorrel (Rumex acetosella):

Sheep sorrel is a communist. It waves the red flag wherever it moves in and it moves in wherever it finds the democratic grasses struggling against adverse conditions. Small though it is, its snakelike rootstalks crawl under and among the grass roots and send up new reds among the grass bunches.

Often a xenophobic attitude is revealed, as when a naturalist writes of noxious weeds as aliens that have been naturalized. These aliens must be dealt with in a drastic way, for they are suspected of harboring plant pests, lowering the economic value of the crops; their rank growth and unsightliness is a perpetual nuisance in turf, they are a safety hazard, poisonous, and cause hay fever. The latter was taken from a popular textbook on horticulture.

What are weeds when viewed objectively? They are the primary succession of plants where the soil has been disturbed. Usually they are followed by grasses or brambles. They are indicators of poor soil, showing the observant gardener that his or her soil is becoming too acidic, too poor, too compacted, or too alkaline. Weeds do not, for instance, drive the grass out of a pasture; they merely come in and fill the gap when the soil will no longer support the grass. Thus, weeds are symptoms and not causes of our problems. Spraying for weeds is, again, putting the cart before the horse. Weeds will appear in abundance only if the conditions are right; the seeds lay dormant in the soil until such a time. For example, the fireweed and some fleabanes sprout only after a fire has gone over the ground, others germinate when the land has been ploughed, and some germinate only when there are specific planetary constellations. Analyses of soil in fields have shown that a square foot of soil down to the depth of plowing may contain 7,000 viable seeds representing a number of species. These seeds are waiting for specific conditions before they will grow. By maintaining good soil husbandry, these weeds need not be a problem at all. If the soil does go out of kilter, it might even be a good idea to include a fallow of weeds to restore a balance of the soil organisms and soil nutrients.

Joseph Cocannouer, in Weeds: Guardians of the Soil, speaks of weeds as a blessing in disguise. Weeds are deep rooters; they explore the depths, breaking through the plow sole so that the weaker roots of the domesticated species may follow, providing them with a larger feeding zone. They fiberize the soil, countering compaction. During rainy or windy seasons they hold the soil against erosion. They help bring water to the topsoil by the capillary action of water molecules along their roots. They aid the organisms of the edaphon through exudations and chelates. When harvested, they enrich the compost with minerals and nutrients and in the pasture they provide sources of vitamins for livestock, resulting in fewer veterinarian bills. Following the lead of F. C. King, Cocannouer suggests letting select weeds grow in the garden to serve as mother weeds for domesticated crops. Mother weeds, such as sow thistle, lamb's-quarters, annual nightshade, ground cherry, or ragweed, will let the roots of the domesticates grow alongside into the deeper horizons, making water and nutrients available to them. Other weeds can be hoed and left on the soil as green manure, while still other weeds, such as purslane and chickweed, will provide living mulch for the taller crop plants.

According to Alan Chadwick, healthy weeds, properly managed, create an aura of vigor and health in the garden. He sows a mixture of fava, vetch, sonchus (or sow thistle), rye, senecio (or groundsel), anagallis (or scarlet pimpernel), veronica, plantain, and others mixed in with his cover crops.

According to Robert Rodale, there is experimental evidence that weeds act as insect controlling factors. In a South American study it was shown that weeds among corn reduce the leafhopper by 40 to 53 percent and the cutworms by 68 percent. This, of course, involves the principle of companion plants.

Weeds also aid the soil fauna. Dying root and leaf parts feed the earthworms and the channels left by the deeper roots provide passage tunnels for the earthworms as they travel from the higher to the lower horizons of the soil.

Bargyla Rateaver and Gylver Rateaver list the following companion plant effects in their Organic Method Primer:

Weeds that are soil improvers because they either absorb excess salts and bind them organically or fiberize the soil include goldenrod, nightshade, ragweed, purslane, and shepherd's purse.

Weeds that hold the soil against erosion include ragweed, pigweed, and clovers.

Weeds that attract earthworms and aid the soil with root exudates include stinging nettle, plantain, dandelion, and thistles.

Other weeds work directly as companion plants, such that bindweed helps corn; nettle and yarrow improve the volatile oils in herbs; jimson weed helps pumpkin; lamb's-quarters and sow thistle aid cucumbers and melons; mustard is good under grapes; dandelion helps strawberries; nettles aid the tomatoes; pigweed (amaranth) is good with all nightshades (potato, pepper, eggplant, and tomato); purslane is a good mulch for corn; and sow thistle, yarrow, dead nettle, and valerian are good for all vegetables in general.

Thus it makes good sense to know one's weeds and use them in a dynamic way. It is mainly during the spring sowing that the germinating weeds must be kept in check, so that they do not smother the crop plants. Working the soil about two weeks before planting, letting the weeds sprout, then cultivating again before sowing the vegetable seeds is the best way to accomplish this. Regular hoeing during the early growing season and hand picking within the rows will keep the weeds down between the rows. After the cultivated varieties are strong enough, one can mulch and the weeds should not be a problem. If they are a problem, then the soil is most likely one-sided in an unhealthy way. The few weeds that make it despite should be welcomed as mother weeds or possibly as edible greens. Grasses, which form a succession to the weeds, must be kept out of the garden, for they feed in the same rooting zone as the domesticated species and can be real competitors.

Instead of chemical warfare, flamethrowers, and hysterical reactions, one can enjoy the weeds and even eat many of them, as Ben Harris suggests in a book called Eat the Weeds. Coconnauer writes that many Native Americans made no linguistic distinctions between weeds and good plants, so that the women cultivated the weeds as pot greens and medicines right along with the vegetable crops. The eating of weeds has a long tradition. The stomach and intestinal contents of the Tolland man who was preserved in a Danish bog after having been sacrificed to Odin some 2,000 years ago shows a last meal consisting of a gruel made from barley, linseed, wild flax (Camelina sativa), knotweed, and many different weeds associated with cultivated land, including bristle grass, dock, black bindweed, and chamomile. The Grauballe man, another Iron Age sacrifice preserved in the peat muck, contained a springtime menu of clover, goosefoot, buttercup, lady's mantle, black nightshade, yarrow, wild chamomile, smooth hawksbeard, and nearly sixty others.

Good, common, edible weeds that are found in most gardens include burdock (Arcutium lappa); curly dock (Rumex crispus); dandelion (Taraxacum officinale); lamb's-quarters (Chenopodium album); milkweed (Asclepias syriaca); peppergrass (Lepidium); purslane (Portulaccea oleracea), which used to be grown as a vegetable in cloister gardens; sorrel (Oxalis); sow thistle (Sonchus oleraceus); pigweed (Amaranthus); plantain (Plantago); chickweed (Stellaria media); wild mustard (Brassica arvensis); ground ivy (Glechoma hederacea); and many others. Some of these are eaten raw in salads, some must be cooked, and others have only some edible parts. It goes beyond the scope of this book to go into further detail. Care must also be taken to identify those weeds, such as the hemlock, that are poisonous.