My gardening background came from my family and was built upon through my own trial and error and experimentation over the years.
My Grandparents were homesteaders in the Ozarks in Missouri and my Mother possessed gardening skills that few could begin to match. They relied on their gardens for food year around. My Mother was one of 18 siblings and they all lived off the land. As a result, they placed a very high value on soil building. Healthy garden soils were often considered more valuable than money in the bank.
They were not only experts at growing things but they were extremely knowledgeable on preserving food....a skill which has been largely lost today. How I wish I could have absorbed more when they were here. I often find myself doing something in the garden which makes me think, "now where did that come from?" It almost always comes from my background.
The last surviving sibling from that family is still going strong at 94 years young. Although I don't see her much these days, whenever I get the chance I always try to get her to talk about her vast experience. Priceless knowledge.
Those who live off the land...or have lived off the land...are the true professionals...they don't survive otherwise. Anyone can call themselves a pro. Garden books have very little value to me....but for technical info on ph, soil microbes, etc.
There was a time that 60% of our food was grown, raised , hunted or gathered .
The measure I use is when over 90% of a certain veggie consumed at home for a year comes from my home garden, it feels like that veggie has been mastered at that point. Such is the case here for potatoes, tomatoes, all kinds of beans, onions, carrots, okra, corn, peas, cucumbers, squash, turnips, broc, cabbage, brussels, and peppers....all over 90% supplied from my garden based on the foundation provided from my family.