This is the sort of “between the seasons” period when we sometimes look around for things to do in the garden, just to be outdoors on nice days. And checking the mulch in your shrub borders or flower beds is one of those things than might occur to you.
But why mulch in the first place? Well, mulch can keep down weeds. It won’t prevent all their seeds from germinating, but it can make it easier to pull them. It can insulate the soil from temperature swings, both summer and winter, and help retain moisture so that plants have a constant supply. An absorbent mulch can prevent splash that might pass a disease from the soil to the plants and control erosion from water and wind. And as it decomposes organic mulch feeds the plants and the worms, microbes and other organisms that benefit the plants.
And, it can add to the asthetics of the garden just by providing a unifying feature.
“Should mulch be replaced every year?” No! Replenished perhaps but not removed and replaced.
“Can I use cardboard or shredded newspaper?” Sure, they’re organic and will decompose. But consider that voles can find shelter under the cardboard and shredded newsprint may blow around. And there is controversy as to whether office paper should be used at all because of the various chemicals involved in its production. I’d avoid it as a mulch. Just ship that paper off in your blue bins.
“How deep should mulch be?” Three to four inches is enough, and of course that will be reduced as the mulch composts.
The exception here is around trees or shrubs. Mulch piled against the trunk can serve as an “umbrella” shedding water that the roots need or when it does retain moisture two things may happen: the new roots grow upward rather than down or horizontally and the added moisture can lead to fungal canker and trunk decay. You want to be able to see the curve where the roots go out from the main stem. Don’t create a “volcano”!
Article written by Glenn Palmer, Extension Master Gardener Volunteer.