Your Mulching Questions Answered

Mary Tebo Davis

Learn more about keeping your soils covered with Mary's blog post Mulching - Keeping Soils Covered. Here Mary answers some of your further mulching questions:

  1. Does it matter if your grass clippings have weeds in them? If so, which weeds matter?

Most of our lawn clippings contain other plants beside grass such as clover, dandelions, violets - whatever makes up your lawn. These are all fine. Things get pretty well chopped by the mower and should just break down. (Just remember that the best thing to do with lawn clipping is to mulch them in place and help build the soil and the lawn area. However, collecting grass clippings occasionally to use somewhere else on your property is alright too.) If you were mowing a brush-filled area and not lawn, invasive plants like Japanese knotweed should never be mowed, as one little segment can start a new invasion. This time of year fall leaves on the lawn can be run over with the lawn mower are a great form of mulch. The best gardens I have ever visited use shredded or chopped up leaves as mulch in their gardens!

2. Can you put leaf and grass mulch over wood chips? Should I clear the woodchips and replace with the grass and leaves? 

Never waste your energy or the resource by clearing left over wood chips, mulch or other soil coverings. Feel free to add a little more on top if the soil is exposed or what is left is very thin.  When using fresh grass clippings as mulch, lay down a layer of only ¼ inch thick. This will allow the grass to start to break down before it begins to smell or rot. Thicker layers have a tendency to remain too wet and can invite mold and create smelly decay issues. Once they are composted you can put a thicker layer down.

3. If we invest in chipping/shredding, can we chip buckthorn or bittersweet?

You wouldn’t want to do that if they are in fruit, as their seeds will make it through the chipper. If they are not in fruit, chipping them and using them on your own property would be okay. Honestly, when you are talking invasives you want to look each one up and see what the recommendations are, as each plant is very different. Some can sprout from almost nothing, like Japanese knotweed, and others not so much. Check your resources. The UNHCE fact sheet on invasive disposal is helpful at:

4. How about woody garden refuse like raspberry canes or hydrangea stalks? What if the raspberry canes had any of the cane blights? 

This is a tough one. If the plants are healthy I would chip all those stalks, but wait until after spring insects emerge as many insects use these stalks to overwinter. The rule of thumb is to wait until later spring when daytime temperatures are consistently over 50 degrees. If there is a known disease you should probably remove any diseased plant material in the fall. Adding it to a burn pile may be an option.

5. Given the tremendous amount of rain this summer in some locations, there were many different kinds of mushrooms and fungi that popped up. If there are spots that might have been fungus on some of the fallen leaves, does it make sense to mulch and then leave them in place?

If you have a type of disease that will winter over it would be better to not compost it, but then you would want to be sure of what the fungal spots are and if they are really a problem. I wouldn’t be too worried -  if you weren’t there to clean it up nature would take care of it over time, finding a balance again.

6. Do you have overall advice for people who are game to try the homemade mulches? What are the best sources of information? 

Permaculture principles include the concepts of produce no waste, and use available resources. This makes so much sense when we think of our yards, landscapes and gardens. Leaves, lawn clippings, twigs (under 6 inches are considered ramial wood), all of these are the basis of soil building and a healthier ecosystem. I know quite a few people now who gladly take their neighbors' leaves and turn what others see as waste into black gold. I think that whichever way you decide to go, first take time to try and look at the whole picture, not just part of it: the inputs and outputs, the energy used, the impact to the wildlife that share your yard, etc. For example, does it make sense for one person to spend money on a chipper? What resources go into making and maintaining them, and what are all the costs? Can instead the neighborhood rent one in the late spring, or everyone pitches in to borrow one or find a used one and a person who can maintain it?  In the fall can you just use your existing mower to take care of the leaves and small twigs and turn them into mulches and compost? Is there a local arborist who can drop off free wood chips when they are working in your neighborhood?  There are no black and white answers, but lots of gray to contemplate to see what works best for your situation.


Mary Tebo Davis
Urban and Community Natural Resources Field Specialist
Full Extension Field Spec
Phone: (603) 641-6060
Office: Cooperative Extension, Taylor Hall, Durham, NH 03824