Mulch: Mulching material can be bark, compost, dump rock, wood chips, and a few others. Mulching is essentially spreading a layer on top of the soil to retain moisture underneath. Mulching keeps the soil cooler in summer and warmer in winter. It aso prevents weeds from growing and if organic, will decompose and improve the soil. Mulching will benefit the whole garden and especially cooler season plants like lilies and more thirsty plants like hydrangeas and roses.