Below is a picture of the charcoal experiment where I added unburned natural charcoal to the soil. The charcoal pot is the one on the right and seems to be doing the best. The plant without any fertilizer did die out and the one with just fertilizer, in the middle, is doing poorly. I’ll try this with different plants next year as this particular Verbena didn’t do well in other areas.
Charcoal in Soil Test
Butterfly Gardening 