Gardening: organic fertilizer

One thing I always forget as a gardener is that plants need food. I remember the watering and the weeding, but that's about it.

Preparing food for plants is more chemistry than cooking, however. I had to refresh my knowledge of NPK (nitrogen-phosphorous-potassium) and try to figure out how much of each thing was needed. Apparently you should test the pH of your soil before fertilizing. I say apparently because I didn't bother - I was just happy I remembered that they need food at all.