Cedar mulch in flower and shrub beds cuts down on weed growth and protects plants from temperature extremes. It also conserves moisture. Mulched beds can have moisture levels twice as high as unmulched beds, according to Cornell University Department of Horticulture. Additionally, gardeners spend about 2/3 less time weeding mulched beds.
Cedar mulch provides an organic alternative to landscape fabric. In addition to keeping weeds down and preventing moisture loss, cedar mulches act as insulation, keeping soil warm in winter and cool in summer. Scientists believe the natural repellents in cedar oil may repel some insects.
Cedar mulch is commonly used in beds containing shrubs and flowers. Gardeners typically apply 2 to 3 inches after putting in plants. Additionally, cedar mulch is applied around the trunks of young trees to minimize weed growth and conserve moisture. Cedar mulch can also be used to line the paths of raised garden beds.
Cedar mulch tends to turn gray and break down after two or three years. Many gardeners apply a new layer of mulch over the old layer. According to Cornell University, though, this practice can suffocate plant roots and promote disease. Cornell University advises gardeners replace mulch every two to three years.
Cedar mulch in flower and vegetable beds causes soil to warm up more slowly in the spring, possibly slowing the growth of plants. Fresh cedar mulch has a high carbon-to-nitrogen ratio, meaning it initially makes nitrogen less available to plants. Additionally, fresh cedar mulch may contain toxins that could leach into the soil, damaging young plants.
Rake mulch away from young plants in the spring to warm the soil and prevent suffocation. Add extra nitrogen to the soil by applying manure, compost or a synthetic fertilizer and always use cedar mulch that's been allowed to weather for two or three months.