Interplanting, Ancient Roots

INTERPLANTING IS ANCIENT. It predates agriculture. Interplanting even predates the dinosaur, going back to the first plants growing side-by-side on planet EARTH. Indeed, interplanting is a natural ecological phenomena, existing much like the stars in the night sky.

On farms and gardens, interplanting is sometimes called companion planting. Ancient farmers observed natural interplanting or companion planting in their fields, along with winds, rains, heat, cold, insects, solstices and lunar and planetary movements across the sky. Today, much of the natural interplants occurring in farm fields and gardens is derisively referred to as weed growth (though major crops like maize and wheat still contain the genes of weed ancestors). Indeed, it is a value judgment when native wildflowers like prairie sunflowers are labeled weeds and destroyed by cultivation or herbicides.

In the U.S. state of Tennessee in the 1930s, during America’s Great Depression, the insect factor in interplanting was first subjected to scientific experimentation by an entomologist named Marcovitch. Writing in a 1935 issue of the Journal of Economic Entomology, a still extant publication of the Entomological Society of America (ESA), Marcovitch traced his interest to experiment station reports by other entomologists. Much like the ancient farmers who based planting decisions on empirical and astronomical observations, an entomologist writing in 1906 “advocated for the control of the melon louse the planting of mustard or kale or rape around the melon field. The lady beetles would thus become plentiful after feeding on the cabbage aphids and be ready to attack the melon louse.”

Marcovitch’s penchant to begin the modern era of experimental companion planting was also inspired by a 1929 entomological report that woodlots fostered populations of aphid-eating syrphid flies that destroyed aphids in garden peas. In contrast, pea fields away from woodlots were devastated by aphids and sometimes yielded no crop. Figuring that aphid damage to vegetables was a consequence of an absence of biological control by aphid natural enemies, Marcovitch began a series of scientific interplanting experiments to boost natural biological control in crop fields.

Tennessee turnip strips planted in March yielded aphid natural enemies like lady beetles and small parasitic wasps that migrated later into adjacent strips of peas, beans, corn, okra, cotton, cucumbers and watermelons. Aphid populations declined in the main crops, thanks to the adjacent natural enemy-laden turnip rows. In contrast, “control” watermelon plots lacking adjacent turnip rows to provide natural enemies were destroyed by aphids early in the season.

Since Marcovitch’s pioneering 1935 report in the Journal of Economic Entomology, books have been written on interplanting experiments to increase natural biological control in crops.