Answer: The best approach is to spread a 4-5" layer over the top of the soil and dig it down to a depth of about 8". Plant your perennials, then mulch over the bare soil with another 2-3" of compost. This will suppress weeds, moderate soil temperatures and slow water evaporation. As this mulch decomposes you can dig it into the soil and add fresh compost. Best wishes with your perennial bed!
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