(Photo caption: part of the wonderful beautyberry, that is way to large for its current spot).
(See part I). Most of my other garden mistakes have had less severe consequences. The next mistake has to do with under or over-watering, or letting the soil stay too dry (from neglect) or too damp (from mulch). The Irises I had a picture of in the first "mistakes" entry were victims of too damp soil due to mulch-I swore that the mulch was far enough away from the iris rhizomes, but the rain may have washed it into a pile on top of the rhizome. I found them too late, after they were rotted and gone. A similar thing happened to my pricey Flame Echinacea. An example of under-watering, or putting a plant in an area that was too dry, is the Lobelia cardinalis (Cardinal Flower) in a dry-ish raised bed (though I admit to doing this twice! Don't learn from your mistakes is the motto here!)
Failing to cage a tuber or root (those that are tasty to rodents) under ground is another mistake. When I first moved here, I planted tulips, not realizing the extent of the mole and vole incursions into my neighborhood. The tulips were eaten forthwith and just never came up (my personal "Feed a Vole" program). The sweet potatoes fooled me, though, with their beautiful, lush foliage. In the fall, I dug up the sweet potato bed- there they were, large, lovely sweet potatoes. It was only when I tried to lift them that I found they had been eaten from underneath, leaving just beautiful shells of sweet potato skin. Every time since I have planted tulips, I have dug a trench, and built a cage of garden cloth (square wire fencing, small gauge) right in the trench, with a top to deter squirrels. Or I have planted daffodils, poisonous to rodents (and hardier than tulips anyway). When I try sweet potatoes again, I will do something similar, though use a much larger cage.
Not marking a plant and accidentally digging it up is another obvious problem. I or my husband have dug up perennial hibiscus (they die back to the ground and are easy to miss), various bulbs, and other woody perennials that die back. I use metal garden markers with indelible pens and wax markers to mark their locations (and they do, until my little nephew pulls them out of the ground or we run them over with the mower).
Composting kitchen utensils, even sharp knives (ouch! You do not want to get cut while your hands are in compost- the infection possibility is huge!)
Not bothering to return a defective or dead plant within the warranty (most companies are good about these returns).
Plant non-drought tolerant plants under trees or under a roof overhang- the trees or overhang will divert rainwater.
…and I could go on and on….
Happy mistake-free gardening!