Does shredded CEDAR mulch really repel insects?

californianMay 27, 2011

I bought a bag of shredded cedar mulch and it says on the bag that the cedar repels insects. I did a websearch and several websites say it repels aphids, earwigs, and ants. Can anyone verify this? If so I plan to put it under my sprawling tomato vines to keep slugs, snails, roly polys, and earwigs from eating any tomatoes touching the ground.

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crankyoldman(z5 NY)

It repels fire ants. I used to use it for that in Florida. Put a layer of cardboard or six sheets of newspaper and a good thick mulch of cedar, cypress, or eucalyptus, and the fire ants won't come through it.

    Bookmark   May 27, 2011 at 9:25PM
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does it have any effect on the soils PH?

    Bookmark   May 27, 2011 at 11:23PM
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Cedar oils definitely repel some insects, I've used it with success on fleas and CedarCide is a decent mosquito repellent, it's 1% cedar oil, 99% essence of Juniperus virginiana. Redwood mulch is good for CA soils, I'm less sure about cedar.

    Bookmark   May 27, 2011 at 11:57PM
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'Cedar' is a generic term that is used to refer to several types of trees, most of which are not true cedars (Cedrus species) at all. On the west coast, 'cedar' most likely refers to Western red cedar, Thuja plicata. In other parts of the country, 'cedar' usually refers to some sort of native juniper.

Both contain a lot of essential oils that repel insects, primarily by smell. But neither type repel ALL insects. Mollusks - like snails and slugs - are not typically affected, although their presence may be reduced to some extent just because they are not inclined to creep over the rough surface. However, I would not rely on ANY type of cedar mulch to deter slugs/snails -- you need to bait for these types of garden pests.

Insects that will be deterred are some types of ants, cockroaches, termites, fleas, moths, some varieties of flies. Cedar wood chips (either type) are often used as pet bedding because of this property. Also some desirable garden inhabitants, like butterflies, will avoid cedar. But other insect pests will find either type of cedar a welcome habitat, as they will burrow and live in the moist, dark recesses of the thick mulch layer and feed on the decomposing wood. These includes earwigs, vine weevils, pill or sowbugs (roly polys) and various beetles.

Western red cedar is a valuable timber tree with very durable, long-lasting wood. Western red cedar mulch is a by-product of this industry but still tends to be pricey. Eastern red cedar is a weed tree and mulches made of this type of wood tend to be rather inexpensive.

    Bookmark   May 28, 2011 at 10:39AM
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This will lower the Ph (acidic mulch) and it will tie up the Nitrogen in the soil. the little good you might get from this will be outweighed by the bad, I would not recommend this for tomatoes. I would recommend it for acid loving plants such as brambles, though.

    Bookmark   May 29, 2011 at 12:47PM
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FYI I used shredded cedar mulch in my tomato garden last year and had great yields and no problems.

    Bookmark   May 28, 2014 at 7:20AM
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"Cedar" mulch,( from whichever species), will not acidify your soil. Been disproved for a long time. Rainwater has a pH of 5.6 and doesn't acidify soil either.

Neither will it lock up nitrogen in the soil if it's laid on the surface and not mixed in.

    Bookmark   May 28, 2014 at 11:55AM
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As long as the essential oils in the mulch are present an volatile many insects will find cedar and eucalyptus repellent. As those oils evaporate the mulches become less effective as a deterrent.

    Bookmark   May 29, 2014 at 7:02AM
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