Inside The New York Botanical Garden

Tip of the Week: Compost, Mulch, and Good Soil Practices

Posted in Uncategorized on April 19 2010, by Sonia Uyterhoeven

Sonia Uyterhoeven is Gardener for Public Education. Join her each weekend for home gardening demonstrations on a variety of topics in the Home Gardening Center.

This week we’ll celebrate Earth Day by focusing on sustainable practices. In the Home Gardening Center from Thursday through Sunday we’ll present demonstrations on composting, compost teas, vermicomposting, and vegetable gardening.

You can greatly improve your soil by adding compost to your garden, as I wrote in last week’s blog.

Compost can be added any time, but is usually applied in the spring and often repeated in the fall after garden cleanup. Spread a half-inch to an inch of compost around your trees, shrubs, and perennials, on your lawn, and in your annuals and vegetable gardens. In established gardens, spread the compost on top of the soil, where it will eventually seep into the ground below; or you can lightly fork it over. This will improve the first 6–15 inches.

Shredded leaves are a cheap and easy way to add organic matter to your garden. They decompose quickly and add nutrients to the soil. To shred the leaves, run your lawn mower over them or use a leaf shredder. Leaves that aren’t shredded take longer to break down and if too thick can become matted, impenetrable clumps. Remember to use caution when using a leaf shredder or any powered equipment. Avoid wearing dangling scarves or loose clothing.

Mulches can be applied atop compost or leaf litter to suppress weeds, add organic material, and reduce the evaporation of moisture from the soil. The layer of leaf litter or compost will provide extra nutrients and break down more quickly than the mulch.

Add a maximum of 2–3 inches of mulch to your garden. A deeper layer could deprive the soil of oxygen and block moisture. Never pile up mulch at the base of a plant; it will encourage rot and infection. The best time to apply mulch is in the spring, once the soil has warmed and after a heavy rain.

Shredded leaves, bark chips (fine or coarse), pine needles, grass clippings (not too deep otherwise it will become anaerobic), and straw all make good mulches. Fine mulches will break down into organic matter sooner than coarse mulches, which will take a few years to decompose.

Vegetable gardens can be mulched with straw, newspaper, and grass clippings while perennial gardens do well with shredded leaves and fine bark mulches. Do not use grass clippings on the vegetable garden if you treat your lawn with chemicals.

Remember that soil compaction prevents healthy growth by reducing the amount of oxygen available in the soil, preventing proper drainage, and not allowing soil microbes the air and the space that they need to survive.

Though it’s tempting, do not garden too early in the season when the ground is super saturated from winter rain and snow. Likewise, avoid gardening after a heavy rain—you will only compact the soil and cause more harm than good.

In cold climates, the natural process of freezing and thawing breaks up the compaction in the soil. Staying out of your beds, building raised beds, and creating paths are all good ways of avoiding compaction in your garden.

Traditionally, rototilling was a favored way of breaking up soil. But as it destroys the soil structure and creates a hardpan, many feel the drawbacks outweigh the benefits, and so leaving beds undisturbed unless heavily compacted seems to be the trend these days.

Forking over the soil is often a good way to break compaction. For those of you who attended Barbara Damrosch’s talk in February, you will remember that she uses a broadfork, which aerates the soil without damaging soil structure or mixing the layers.