Fall mulching or composting for garden improvement

By Doug Thompson

Houston County Master Gardener Intern


There’s still time this fall to improve your garden and flower bed soils for better growing conditions next spring and summer. The warmer temperatures that we’ve experienced this fall have extended the season, which still allows us to add mulch and organic matter to our gardens. This has the potential to improve the organic matter content, retain moisture and actually raise the temperature of soils throughout the winter. This increases microbial action in the soil to release nutrients that will be more available for growing next spring.

There are many ways to go about this. If you have tilled soils and prefer the look of a carefully tilled and clean garden bed, you can add well-decayed compost or mulch to the bed and till or turn it into the soil. The more broken-down, composted plant fibers are much easier to handle in this method, since they easily incorporate into the soil, whether you use a tiller or simply fork and turn compost into the earth.

It is pretty hard to apply too much, provided the material is well decomposed and crumbly. An alternative is to use finely chopped material, such as leaves or stems that have been processed through a chipper or shredder or even leaf material that has been gone over several times with a power mower.

Even a heavy compost cover will readily disappear with just a little tilling. If you have larger, un-chopped plant materials or mulches, they can still be turned under, but a lot more work is required, especially if you use a garden fork. Garden tillers tend to clog with roots and stems with these materials.

A second method is to simply pile compost or mulch on the surface of the tilled bed and leave it in place over winter. This method provides a little more protection for the soil, maintains a slightly higher temperature and conserves moisture.

In spring, the mulch can be raked aside and the bed will be ready for tilling and planting. The lower layers will compress and decay slightly over the winter and provide nutrients and organic matter to the soil during periods of warmer temperatures. However, weed seeds in the plant material can fall out and germinate in the spring, so early tillage is important.

A modification of this method is to place heavy paper bags or several layers of newspaper under the compost or mulch. In spring, you leave the material in place and plant your transplants or seeds in small piles of dirt nested into the heavily covered bed. The paper can help reduce tomato blight later in the year. Keep in mind that decaying material uses nitrogen so you may need to add some amount of manure or nitrogen-rich fertilizer in the spring.

A third method is similar to the second except you would start a bed on untilled, unprepared soil or even weedy or grassy areas.

Simply lay the heavy paper down over the entire area. Our local feed mills discard hundreds of heavy paper bags each week and they can be easily recycled for gardening. Be sure to remove any strings in the bags and overlap the flattened bags or papers by about 6 inches. They can be split and open to cover a larger area. Then add large amounts of compost or mulch (up to 24 inches high) to build up a somewhat raised bed. By spring, the bed will be compressed so you should add even more mulch or compost to build it back up to 24 inches. Then, as planting time nears, again nest small piles of dirt in the heavy compost, and plant directly in them.

The heavy compost prevents weed growth and retains moisture throughout the summer. Root crops like beets, carrots, potatoes and turnips do very well in these beds, as do peas and other cooler season crops.

Tomatoes can thrive in these beds, but the soil temperature should be around 60 degrees before transplanting.

By the way, don’t forget to mulch, cover or lay down your more susceptible perennials before winter hits.