Cedar mulch is the winner over pine needle mulch for a key feature: it repels pest insects. Cedar also beats pine needles for fire safety. Composted wood mulch -- but not fresh wood chips -- resists combustion, while pine needles fuel rapid fire spread, according to a joint study by the University of California Cooperative Extension and University of Nevada Cooperative Extension. Cedar chips and dead pine needs are organic mulches that improve soil, insulate against heat and cold, deter weeds and reduce soil moisture evaporation.
Cedar Mulch Features
Aromatic cedar mulch deters termites and cockroaches, making it a good choice to use near the house, garage and outbuildings. It repels some ants and also shortens their lives. Researchers from North Carolina State University reported in the Journal of Economic Entomology that the farther Argentine ants had to walk across cedar mulch to reach food, the shorter their lives. Wood chip mulch doesn't affect the nitrogen levels of underlying soil, notes an article in the summer 2007 issue of the magazine, Master Gardener. The magazine also states that cedar doesn't contain allelopathic chemicals, chemicals some plants produce that are harmful to other plants.
Pine Needle Mulch Features
Pine needle mulch, also called pine straw, doesn't repel insects. Dead pine needles gives ants a comfortable nesting environment. Avoid using pine needles near plants prone to being infested by aphids, mealybugs, whiteflies and soft scale insects. Ants eat the honeydew these pests excrete and protect these plant-harming insects from predators. Keep pine needle mulch away from the house to cut down on the risk of ants coming indoors. In areas of the yard where ants aren't a problem, dead pine needles perform well as mulch.
Pine Needle Uses
The low-profile of pine needle mulch makes it a good choice for areas populated by voles. Keep the depth of dead pine needles at 1 inch until the voles are under control. A deep layer of mulch creates an inviting environment for voles because it allows them to hide from predators. For fire safety, keep dead pine needles away from buildings and any source of possible ignition, such as barbecues, fire pits, tiki torches and smoking areas. Pine needles break down well in compost piles or bins.
Composting cedar mulch makes it resistant to catching fire, unlike uncomposted cedar chips. Pine needles and shredded red cedar had the fastest rate of fire spread and had the second and third highest flames in a combustibility study of eight mulches in a joint study by the University of California Cooperative Extension and University of Nevada Extension. Composted wood chips had the lowest flame height and slowest rate of fire spread. Garden centers sell composted cedar mulch. Whichever mulch you use, apply it carefully so it isn't in contact with the trunks of shrubs and trees or plant stems. It can cause trunk or stem rot, which could introduce disease or kill the plant.
- UC Statewide IPM Online: Ants
- University of California Forest Research and Outreach: Combustibility of Landscape Mulches
- Fine Gardening: Mulch for a Healthy Garden
- Journal of Economic Entomology; Effects of Aromatic Cedar Mulch on the Argentine Ant and the Odorous House Ant (Hymenoptera: Formicidae); Heike E. Meissner and Jules Silverman
- UC Statewide IPM Online: Voles (Meadow Mice)
- Master Gardener; Wood Chip Mulch -- Landscape Boon or Bane?; Linda Chalker-Scott, Ph.D.
- UC Agricultural Experiment Station: Controlling Whiteflies
- Paul Hart/iStock/Getty Images