Q: Can I use black plastic rather than clear for soil solarization? I want to remove weeds from part of a pasture for a garden next spring.
A: Unfortunately, black plastic will not work. The process of solarization is supposed to heat the soil enough to kill weed seed and diseases. Black plastic shades out anything growing beneath it but it kills only annual weeds, not perennials. The shiny black color reflects a lot of sunlight so the soil underneath is not heated very much. On the other hand, clear plastic doesn’t reflect sunlight. Heat, formed when the light hits the soil, is trapped under the plastic and heats the soil appreciably. But your real problem is not the color of the plastic. It is simply that solarization only works during the heat of summer, not in winter. All this doesn’t mean you won’t get some benefit by covering the ground with black plastic now. Some of the grasses and weeds will surely be killed, just not as many as true solarization would kill.