Can I use cedar shavings as mulch in my vegetable garden around squash or tomatoes specifically?


Can I use cedar shavings as mulch in my vegetable garden around squash or tomatoes specifically?


Jonathan Foster, Home Horticulture Outreach Professional

Cedar has at times been a controversial choice for mulch, due to concerns over 1) its naturally occurring biochemical properties having what’s known as allelopathic effects (that is, inhibiting the normal growth of other nearby plants, though to be an evolutionary tactic to reduce competition) on plantings or seed germination, and 2) worries that its naturally occurring oils, which may have some insect-repelling properties, would decrease pollinator activity for the plants nearby. Per this Washington State Univ Extension fact sheet “Using Arborist Chips as Landscape Mulch (free download as a .pdf), these worries have not been supported by experimental evidence.

In general, mulches with larger individual unit size (i.e., a shaving versus an arborist chip) work better because they suppress weed growth and soil water loss via evaporation while still allowing good gas transfer, whereas smaller units can compress into thicker, matted layers. But if you have a ready supply of the shavings and they are true slivers of wood (not powdery or sawdust-like), I think you’ll be fine using them in your garden. Note that there can be nitrogen deficiencies in the boundary layer between the soil and mulch, due to increased microbial activity as they go to work decomposing the mulch–this helps to inhibit germination/growth of weeds, but it could be a problem if you are planting from seed, and I wouldn’t work the mulch into your soil at all until it’s naturally composted (as that could increase the zone of nitrogen deficiency). Keep in mind, as well, that cedar is naturally resistant to rot, so it may take longer to break down in the garden (helpful for keeping inexpensive mulch on the soil, less helpful for long-term conditioning of the soil).

Please see this previous Ask an Expert response for more information on mulching in general.