David C. Deardorff - What’s Wrong with My Marijuana Plant?: A Cannabis Grower’s Visual Guide to Easy Diagnosis and Organic Remedies

Whether you are a home grower with a couple of marijuana plants or a commercial grower with hundreds of plants, this book will help you diagnose problems and find solutions. Disorders (such as unhealthy growing conditions), pests, and diseases are all included here. You can treat all these problems by improving growing conditions, using biological controls, or applying safe, organic remedies.

We are botanists, plant pathologists, and writers. Weve owned nurseries and traveled the world on botanical adventures. In this book, we have compiled the most recent research to help you grow healthy cannabis. The United States government considers cannabis an illegal crop, resulting in no U.S. Department of Agriculture (USDA) guidelines, no Environmental Protection Agency (EPA) standards, and virtually no university research on acceptable treatments for pests and diseases or on the efficacy of those treatments. Research on organic cultivation of cannabis is relatively limited. To find the best organic methods, we have worked with licensed legal growers who use organic practices and we have relied on research from European sources, the Organic Materials Review Institute (OMRI), and other scientific literature.

Every state in the United States that has legalized marijuana has its own statutes and guidelines. Be sure to find out what is permitted in your location, because we are not legal experts. Finally, we are not medical practitioners and have conducted no research on the medicinal attributes of marijuana. Please consult with your doctor or health care practitioner for advice on its medicinal uses.

Whatever your intended use of cannabiswhether as a medicine, relaxant, mood enhancer, ritualistic practice aid, or vehicle to alter perceptionyou must inhale, ingest, or otherwise absorb its active ingredients. Any nonorganic, synthetic pesticide used on plants winds up inside you. Synthetic chemicals such as pesticides damage human health and the living community of which we are a part. Choose organic techniques to protect yourself and the environment.

No matter where cannabis is grown, virtually no health and safety standards exist for growing it. Because it is considered illegal in many places, research is lacking and testing is not standardized. Recent media coverage has revealed that pesticide residue on marijuana is an escalating problem. Labs that have performed tests have frequently found contaminants such as pesticides and heavy metals. These pesticides include fungicide and insecticide residues at levels sixteen-hundred times higher than the legal limit for food plants. This is alarming. It just makes sense to do everything possible to eliminate this threat to the health of cannabis growers, users, and the biosphere.

People have cultivated cannabis for medicinal, spiritual, and recreational purposes for ten thousand years. In 2008, an archeological dig of a shamans grave in China revealed the earliest record of its medicinal use some twenty-seven-hundred years ago, and evidence shows that ritual use is more than four thousand years old. Recreational and mood-altering uses are likely just as ancient. The Greek historian Herodotus, writing in 440 BCE, mentions its euphoric effects in his Histories. In more modern times, people have made paper, clothing, and rope from hemp fiber and oil and milk from the seeds.

Because of our relationship with this important plant, humans have carried cannabis around the globe for so long that its difficult to determine exactly where the plant originated or even how many species of Cannabis exist. One example of cannabis proliferation comes from nineteenth-century Europe, when ships carried the seeds around the world so that sailors could sow them in every port to ensure a ready supply of hemp rope for rigging. Such practices make it a challenge to determine the natural history of cannabis. In addition, its botanical classification and nomenclature are always changing.

Knowing something about the botanical classification and nomenclature of marijuana helps breeders and growers make informed decisions about what strains to grow and how best to nurture them. Marijuana growers use the term strain where other horticulturalists or agriculturalists would use the terms species or cultivar (cultivated variety). By knowing and recognizing a specific strain, you know something about the genetic background of the plant you want to grow. The genetic background determines many of the plants cultural needs (such as whether it prefers warm or cool temperatures, how big it will get, and its light requirements for flowering).

Although botanists have been arguing about this for more than two hundred years, two different kinds of cannabis plants are generally recognized and widely cultivated: sativa and indica. Authorities differ as to whether these two plants are, in fact, different species (