Answer: Recent research indicates that red mulch can indeed increase tomato harvests by up to 20%. The mulch reflects far-red light wavelengths upward into the tomato plants, stimulating growth and fruit development.
Gardener's Supply (ph# 800-863-1700, http://www.gardeners.com) sells red plastic mulch.
Mulching peppers with aluminum foil has a similar effect of directing light back up into the plant. It also seems to confuse some insect pests. I would put the foil down right after transplanting, and remove it once the plants begin to form peppers.
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