People frequently talk about family resemblance—eye color, hair color, height, shape, etc. It’s no different in my own family. My second-cousin, Winnie, is the spitting image of my grandmother. My father and his cousin Håkon could be twins. My nephew looks very much like my father did when he was a child. We even have similar mannerisms. Last summer, at a little league game, my sister said about my nephew, “Look at that, he’s standing just like everyone else in our family.” I hadn’t thought about it before, but she was right. He was standing exactly the way my father and grandmother stood.
Plants have families, too, and therefore family resemblances and characteristics. I’d known for a long time, for example, that almost all plants with square stems and fragrant leaves are from the mint family. Until I took a botany class last summer, however, I did not know that carrots are a member of the parsley family or that potatoes and tomatoes are in the same family.
Who cares, right?! Well. Knowing a plant’s family can help you figure out growth habits and sun preferences. And, if you have a vegetable garden, knowing that potatoes and tomatoes are in the same family (they’re both nightshades, incidentally) is imperative for proper crop rotation. Rotating crops (a three-year cycle is ideal) ensures the soil gets replenished and any pests lingering in the soil won’t find a host.
Both tomatoes and potatoes are heavy feeders and are prone to fungal diseases and pests. If you didn't know about the "family resemblance," you might think you were rotating properly and inadvertently deplete the soil further and potentially encourage the fungal disease and pests common to this plant family.
I took the class because I wanted to get better at plant identification. I’m better now but wouldn’t consider myself an expert and frequently refer to the text from the class to help me figure things out. If you’re interested in becoming better at plant identification and/or understanding the characteristics of particular plant families, I recommend the text, “Botany in a Day—The Patterns Method of Plant Identification” by Thomas J Elpel.