Don’t toss out that free fertilizer

Even in gardening, the best things in life may be free. Is your lawn covered with fallen leaves? Remove them with your mower if they’re dry, rake if they’re wet, but please don’t put them out at the curb for pickup. They’re loaded with nutrients they’ve taken from your soil, but you can return those nutrients by keeping the leaves on your property.

The National Wildlife Federation blogged “don’t rake your leaves,” and they’re dead wrong about that. Leaving leaves lie are destructive to your yard and soil, gathering them is beneficial.

Spread shredded leaves on bare garden beds as thickly as you can. As they deteriorate they’ll supply your soil with organic matter that improves clay soil drainage, and helps sandy soil retain moisture. Decaying leaves also provide nitrogen, phosphorus and potassium, while feeding earthworms and the microscopic creatures in your soil that make it fertile.

Don’t spread whole leaves, since they tend to mat, and that mat will prohibit moisture and oxygen from reaching your soil. Leaves can be shredded easily by your mower or leaf blower-vacuum that shreds as it picks up leaves. If you’ve raked them into a pile, you can put a couple of armloads of leaves at a time in a galvanized trash barrel and shred them in there with a weed whacker. Some suggest letting pets or children or even adults jump on a pile of leaves before shredding it. Or if you’ve bought a shredder, drop leaves into that. The finer they’re shredded, the faster they decay.

You can run over fallen leaves on your lawn without the grass catcher, letting shredded leaves lie on your lawn, nourishing it. Lawn grasses grow this month and next, creating a thicker lawn. That’s one of the reasons we fertilize lawns at this time of year.

If and when our soil freezes, you can use shredded leaves as mulch around perennial plants, taking care to leave a space between mulch and stalks or trunks to avoid Phytophthora crown and root rot. The mulch is intended to prevent frost’s heaving plants out of the soil.

You can use needles from evergreens for mulch, but they’ll keep their tree or shrub’s roots safe from freeze damage if left in place, so I’d caution against raking them away from your own tree or shrub. Tree and shrub roots are more vulnerable to freezes than the exposed upper part of the tree or shrub.

Using such needles will not change the pH of your soil, that acidity being confined to the surface on which they lie. If you get leaves from neighbors or friends who have used one of the insecticides that will kill for a full year, I’d set them aside in bags to wait for summer or next year. Otherwise you might be poisoning the earthworms or arthropods, bacteria or fungi in your soil that are the living feeders of your plants.

Once these shredded leaves have been wetted, they usually don’t blow around. I’ll weight them on garden beds by topping them with soaker hoses. If you do have problems with leaves blowing, you can dig a trench and bury them, covering them with soil. They’ll disintegrate even quicker when buried in that manner, as will kitchen wastes. If you don’t have room for a compost pile or your homeowners’ association forbids compost piles, you can still enrich your soil by “trench composting.” Some people dig a trench and only fill in those parts in which kitchen waste has been discarded. One trench may last for more than a month.

You could also pile your fallen leaves on a compost pile, hastening decomposition by the addition of grass clippings or shredded spent plants or rabbit manure, for instance. Incidentally, shredded paper and newspaper are good additions to the compost pile too.

Improving second bench soil, scoured by ancient river floods and baked in the sun takes time, patience, and as much organic matter as we can muster. Fallen leaves are a treasure, and when I was able bodied, I used to drive through neighborhoods and ask folks bagging their leaves if I could have them for my garden. Unless they’d promised them to another gardener, all readily agreed, and some even helped me load them onto my little pickup.

One year I accumulated so many bags of leaves I was able to spread them ankle deep over my large garden. Although I had often said I couldn’t have too many leaves, they lay so deep, most were still in place the following spring when it was time to plant. We had to rake the leaves aside to let soil dry enough for tilling, although we could have just scraped out rows and planted in untilled soil, like Ruth Stout’s “No-Work Garden” books describe.

This story was originally published November 18, 2015 at 2:37 PM with the headline "Don’t toss out that free fertilizer."