On Wed, 13 Jun 2007 18:03:42 -0700, Sheldon wrote:
Actually anything that impedes evaporation keeps the soil from
cooling... evaporation is what cools soil, the more air circulation
the more the soil cools.
........ true

Most mulches (unless highly reflective and
porous) act to keep soil warmer... dark mulches can kill plants by
causing roots to literally cook.
............ up here in zone 5 mulch is used to keep the soil cool.
tomatoes are never mulched until the soil temp is high enough that it
wont impede growth. and mulches are used to moderate soil temp,
including keeping the soil cold under fruit trees in spring so they
wont blossom out to soon. Ingrid