Complex sentence: Weeds should be removed before planting by preparing the land adequately, and they should subsequently be controlled during the first four to five years, until the shrubs are high enough to shade out the weeds.
Split into simpler sentences: Weeds should be removed before planting by preparing the land adequately. The weeds should then be controlled during the first four to five years, until the shrubs are high enough to shade out the weeds.