I was going to make some leaf mulch with the leaves that I’ve gathered from my front yard. I was going to layer the leaves with city compost (5 ” of leaves to 1/2″ of compost) in a large old plastic garbage pail. I have a couple of questions: 1. The leaves from my Norway Maple (a city tree) have large brown spost on them. The spots look like a rust spot. Is it OK to use these leaves for a mulch? 2. Should I drill holes in the side of the garbage pail to get some air flow? Thank you for taking to time to answer these questions.
It’s definitely OK to use these – they likely contain a fungal disease called tar spot. The best thing to do is to rake all those leaves up and have them collected by the City. The fungi overwinter on the leaves, so would return next year. My neighbours have maple trees with tar spots on their leaves that (unfortunately!) have returned every year for the past few years. However, you can use other autumn leaves (I hope you’ve got some that aren’t spotted)- rake the leaves into a pile then shred them (they should be thoroughly broken up). Also, don’t worry about the tar spot that much, it looks unsightly but won’t kill or damage the tree.
Mulching leaves is often done in outdoor bins, where air and the elements can get at the leaves – so it makes sense to drill a few holes in the base and sides of your pail – this helps drainage and permits air to enter, preventing the contents from getting slimy. When the pail is nearly full, sprinkle the leaves with some water, stir the contents around a bit, close the pail and forget about it. After about a year, the leaves should have turned into a nice crumbly mulch. If you leave it to “age” another year, it will rot even more and can be used to help condition your soil.
You might like to review our Gardening Guide — Using Mulch in Your Organic Garden