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MASTER GARDENERS: To till or not to till

Wally Peck

It is late October, most everything is out of the garden or annual beds, and the question is, "do I till now or wait until spring?"

Along with fall tilling, adding several inches of organic material to the soil at this time goes a long way to improving soil quality. The benefit of tilling in the fall is that plant debris and other organic material breaks down much better if applied in the fall.

A shredder is a great way to reduce leaves to a size that will break down readily. Going over the same leaves several times with a mower and then bagging will work, too. If there is grass mixed in with the leaves, so much the better. Avoid mowing areas that have mature weed seeds as they will usually survive to sprout in the spring.

Fall soil is usually drier than in the spring so the tendency to compact the soil and form clods is less of an issue. Be cautious of over-tilling as soil structure is easily destroyed this way. Fall tilling places the leaves, grass or compost in direct contact with soil organisms so the material has more time to break down before spring.

If the soil is wet, leave it alone. Tilling wet soil creates clods and compaction that can take months or years to correct.

If you are in a wind-swept area, an earlier-plant cover crop can protect the soil from erosion. A cover crop also adds more organic material to the soil. Rye grass is a good option as are other choices that will die down after freeze-up.

This is also a good time to add some amendments to the soil to correct pH. Soil sulfur is typically added to lower the soil pH or make it more acid. Soil sulfur is very slow acting so fall application is an advantage. Soil that is too acid can be amended with lime to make it more alkaline or "sweeter." Only do this after taking a soil test and then following the application rates the test recommends.

Some gardeners are in the habit of adding manure to the soil in the fall. Manure is a good source of organic material but can also be a source of weed seeds depending on the source of the manure. Manure should only come from plant eating animals, never from meat eaters. Also there are some herbicides that survive a trip through the intestines of foraging animals and can cause problems in gardens.

If you use commercial fertilizer on your garden, fall is not a good time to apply it. Nitrogen in commercial fertilizer is usually in the form of urea and will break down or migrate below root level before spring planting so wait until spring for that.

With fall work done, rest up and enjoy looking out at a garden ready for spring planting. The seed catalogs should be on their way next month!

More information on getting the garden ready for winter can be found at the University of Minnesota Extension web site at