Before you can plant, soil preparation is a must.

Most home gardens will be installed where there was once a lawn. Regardless of what currently grows in your future garden location, eliminating the existing vegetation is an important first step in soil preparation.

There are many ways to eliminate existing vegetation and prepare the soil for a future vegetable garden. The most common methods are tilling, smothering, herbicide, cover cropping, or a combination of those listed. Choose the method that best suits your style of gardening.

Conventional Tilling or Plowing

• Dig the soil to a depth of at least 6-10 inches.
• Add a two-to-four-inch layer of organic matter (compost) and incorporate it into the soil.

Organic matter will improve your soil structure and will add nutrients to the soil. Tilling also aids in breaking up heavy clay soil or areas that suffer from compaction. As the soil is tilled incorporating organic matter and oxygen, this increases plant nutrients as organic matter breaks down. However, this effect is usually short-lived.

Tilling also destroys the structure of your soil. Loose friable soil is desirable, but be aware that opening the soil up exposes it to air and sunlight which will greatly diminish your soil moisture.

Concerns with tillage

• Over-tilled or pulverized soil has smaller soil particles that dry out quicker, and you can easily develop a ‘crust’ on the soil surface.
• Tilling releases carbon dioxide into the atmosphere.
• Tilling or ‘lifting’ the soil exposes dormant weed seeds that will now germinate.

There is increased debate on whether a gardener should pursue a tilled or no-tilled garden. Much of the information on gardening is borrowed from industrial-scaled agriculture research. There is less research on small-scale or backyard growing, but there are some emerging best practices.

Smothering existing vegetation.

Fall leaves

Rake or mow fall leaves into the area you wish to establish your native plant bed 6-12 inches deep. Allow leaves to remain until spring and then remove/spread out leaves so they are only 2 to 4 inches thick. This is now your mulch layer. Pollinator plants can be planted directly into the soil.

Arborist woodchips

Trees grow well in Illinois and often there are sources of woodchips in most communities as arborists and other tree care professionals perform routine maintenance or tree removal. Sometimes woodchips are even free!

• Apply 4 to 6 inches deep. This will smother most weeds but some more tenacious perennials may grow through the mulch, these are easily pulled.
• When ready to plant, reduce the mulch depth to 2 to 4 inches deep.

Arborist woodchips are more coarse and allow better water and air exchange to the soil. Shredded wood mulch typically knits together forming a “shell” over time. Shredded wood mulch will need to be cultivated periodically to prevent any shell from developing.

Silage Tarp (Black plastic)

This material prevents light from reaching the soil surface killing living plants and inhibiting seed germination. Gardeners can scalp the vegetation with a mower and lay down the plastic or till and rake out a prepared soil surface and then cover. Tilling creates opportunities for seed germination. Covering after tilling kills germinating seeds creating a stale seedbed. Remove plastic before planting.

Cardboard

If smothering is the only goal, cardboard is another possible material. Be sure to remove any tape, labels, staples or othering shipping/packing material. Remove cardboard before planting. Cardboard can become hydrophilic making it a poor option as a mulch.

Paper

Large rolls of paper designed for garden use can be found at many fruit and vegetable suppliers.

Straw

A thick layer of straw can help suppress existing plant growth. Plant in the straw.

Fertilization

Despite being commonly called plant food, fertilizers are not “food” but more like plant vitamins. Plants make their own food using photosynthesis. By applying the appropriate amount of fertilizer we can provide the nutrients plants need to yield a successful bounty.

A soil test is best place to start to see if what nutrients are lacking. Vegetable garden fertilizers have an analysis of something like 5-10-5, 10-10-10 or 12-12-12.

• The first number stands for the percent of nitrogen
• The second number stands for the percent of phosphorus
• The third number stands for the percent of potassium.

Nitrogen promotes green growth, phosphorus promotes root growth and fruit development and potassium promotes disease resistance and root development.

Most Illinois soils have an abundance of phosphorous and potassium, but the only way to know about your soil is a soil test. Results from a certified commercial lab can save you money.