Weeds compete with plants for light, water, and nutrients. Insects, bacteria, fungi, and other organisms eat leaves, stems, seeds, and fruit. For most of human history the only tools were the hoe, the hand, and pulling a sick plant.

In the nineteenth century, gardeners and farmers adopted compounds — many based on arsenic and other poisons — that killed insects and fungi. In the twentieth century, chemistry (including research that also produced poison gases in two world wars) gave us far more potent pesticides and the first herbicides. They were eagerly used. Together with new crop varieties and synthetic fertilizers — nitrogen captured from the air with petroleum energy, and other nutrients mined from the earth’s crust — they changed how food is grown. That “Green Revolution” helped feed a global population that went from under two billion in 1900 to more than eight billion today.

The costs showed up later. Pesticides can (and often do) kill organisms other than the target pest, and some remain on food and in soil for years. Pests evolved resistance, an arms race with manufacturers. Pesticides and fertilizers moved into groundwater and streams, killing fish and feeding algal blooms. Synthetic fertility taught a thin idea of soil — that plants need only nitrogen, phosphorus, and potassium — at the expense of long-term soil life.

Informal vs. legal “organic”

Informally, people hear “organic” as something vaguely natural, grown without synthetic pesticides, better for health and habitat. The legal meaning is stricter. In the United States, certified organic food is produced under the USDA National Organic Program (NOP). NOP lists allowed and prohibited substances and practices. It is not simply “no pesticides” — some naturally derived pesticides are allowed, and some of those are toxic. Pyrethrin insecticides from chrysanthemum flowers are one example: they are toxic to humans and insects, but they break down quickly. It is a rulebook, not a halo.

Other formal parts of “organic” have to do with food additives, preservatives, and how livestock are treated — not only with what is sprayed. The National List of Allowed and Prohibited Substances is the document to check if you ever need a yes-or-no on a product.

Home gardeners are not certified and do not need to be. This handbook uses “organic” in the gardener’s sense: build soil with compost and organic amendments, avoid synthetic herbicides and insecticides, choose open-pollinated seed when you can, and accept that a few holes in a leaf are not a failure.

The NOP rule pages live at https://www.ams.usda.gov/rules-regulations/organic. If you ever sell produce as organic, you will need that rulebook. If you feed your household, you need compost, mulch, and this book.

Some farmers and eaters feel the NOP does not go far enough — it says little, for example, about how agricultural workers are housed or paid. That critique is fair. The program still marks a substantial step away from the mainstream food system of the last fifty years, and it continues to evolve.