Ask Ruth: Wood Mulch

From Dottie in North Carolina:
I have a question about mulch and how long it should “age” before using it. We had a particularly hard winter and that means trees down, and the chippers going full times. My neighbor brought me a LARGE load of a mix of oak, poplar and perhaps some locust mulch. (no pine) How long should this age before using it?

And from Sam in NE Tennessee:
I enjoyed your recent answer on weed control methods but wonder if you could give some examples of mulch. Many experts say NOT to use wood mulch on veggie gardens b/c not only does the decomposing wood rob nitrogen from the soil but it also allows spores to reproduce easily and cause other problems. I don’t have nearly enough grass clippings to mulch my garden (as we are trying to reduce the lawn cutting areas more and more- a catch 22?) and straw always contains so many weed seeds that it creates it’s own set of problems too. Any suggestions on a good mulch for vegetable gardens of large size?

Dottie, I would wait one year before using that mulch, and I would make sure it does not contain any black walnut chips as they are poisonous to many plants. Consider making your own compost with some of the chips by combining them with a nitrogen source like manure or blood meal. Minimum compost pile size is 3’ x 3’.

Sam, if you use wood mulch, balance that addition with inputs of nitrogen so your plants don’t suffer. Straw is my favorite mulch because the stems of straw are hollow so it makes an airier mulch. The main seeds that sprout in my straw mulch are grain seeds, which I consider a free cover crop. I have used free hay as mulch, but hay does tend to contain lots of weed seeds. Some weed-free alternatives might be black plastic, landscape fabric, cardboard, newspaper, and even old carpet. Some people like to plant a living mulch using appropriate cover crops.

Some people hoe on a regular basis rather than mulching, but in dry years, the mulch does help preserve moisture in the soil.