Do you really need to remove grass before laying gravel? Actually, no. However, you may save yourself from a few future issues if you do. One issue is an inability to predict where irregularities in the area may appear once the grass does die off. You may end up with depressions that hold water or washed-out spots where the gravel disappears into the street or other undesirable areas.
If you do decide to leave the grass, there are several ways to prepare to top it with gravel. I can tell you, as any other experienced gardener or yard owner can, that some grass or weeds will eventually appear no matter what method you use. So long as you pull them as they come up, you should have very little problem with your graveled area in the long run.
Gravel Over Grass
Obviously, it would be a waste of time to simply pour a layer of gravel directly on top of established grass. The grass must be killed off and covered to prevent the root system from reviving.
Round-Up or Otho’s Ground Clear are probably the most popular chemical grass and weed killers on the market. There are also more industrial-type weed killers, called soil sterilants, that can do the job. Read all directions carefully to find out exactly what to expect from these products.
Any spray products should be used on a sunny day when there’s a minimum amount of wind. This is especially important if you use a soil sterilant, as any green thing it touches will die. And any rain or other water will dilute the effectiveness of the chemicals.
There is always the possibility that these chemicals can become dangerous pollutants to nearby plants or wildlife, so consider the surrounding area carefully before using commercial weed killers. If you live near a creek or wooded park area, you may want to consider a different method.
It’s also important to protect yourself, your family, and your pets. Wear protective gloves and a face mask and keep kids and pets away from the area for at least 24 hours, longer if the directions instruct you to do so.
Another popular way of killing off surface grass is to smother it, cutting off needed light and air. This can be done by covering the area with heavy plastic (preferably black to hold in heat) that is weighed down around the edges.
Another option is pieces of old, used carpet. Plastic or carpet are slower methods of killing grass. Either method will need to remain in place for as long as a month or more to be completely effective.
Plastic should be removed once the grass is dead, as it can cause drainage problems. Old carpet will generally allow for drainage and some recommend leaving it under gravel since it will last a long time without being easily affected by foot traffic or natural erosion. If you decide to use carpet and leave it in place, you’ll not need to wait as long to spread gravel over it.
Natural Grass Killers
There are a couple of more natural substances that can be effective for killing off grass before laying gravel. One is vinegar, which can be used as an organic grass and weed killer or aid in the growth of trees and discourage garden pests.
Another more organic plant killer is salt. Any kind of salt will work. For a large area, small, granular softener salt can be an economical alternative to more toxic chemicals. But make no mistake, salt can make the soil poisonous to any living organism for years to come, so apply it carefully. Salt is also toxic to aquatic life, so don’t use it around creeks or ponds.
When you’re sure the grass has been completely killed, you will still need some type of ground barrier between the soil and gravel. A barrier will keep any surviving roots from quickly sending up new growth. It will also keep the gravel from being quickly engulfed by underlying soil.
Various types of barriers may be used, depending on the type of space you’re graveling. If it’s a large area, many will recommend a heavy landscaping fabric. You may want to research the pros and cons of this. There seems to be quite a love/hate argument over this popular ground cover.
Cardboard or newspaper are also popular barriers. But these will disintegrate and need to be replaced more quickly, so they may not be the best for a large area. These paper barriers can also tear more easily if there’s frequent foot traffic across areas of gravel. This will allow light and air to contact the soil. Grass and weeds can easily grow up through these spaces, increasing needed maintenance.
Roofing tarpaper or shingles may also be used as an effective barrier against the regrowth of grass or weeds but could be broken by foot traffic or prevent absorption of moisture.
Removing the Grass
Completely removing grass will result in a more professional-looking and longer-lasting gravel bed. Grass can be removed by several methods. Most are somewhat labor-intensive, so you may need some professional help with this.
Damp soil is always easier to work with than rock-hard, dry soil, so it’s recommended that you water the day before so that the soil and root system will give way easier as you dig or till.
Dig it out
Using a flat shovel, grass can be removed with a couple of inches of root system attached. First, chop a straight line about the width of the shovel wide and parallel with the edge of the grass. Then go to the end of the row and insert the shovel several inches into the soil and push under the grass to create a piece of sod. Chop off the piece, remove, and continue.
This grass can be moved to another clear area and watered in well for a grassy surface. Or dead grass can be removed the same way, leaving a smooth even surface for placing a barrier and gravel. Dispose of the dead grass appropriately, especially if it’s been treated with chemicals.
Removing grass in this way also lessens the need for a border to contain the gravel. After adding your barrier and gravel, the surface level should be about the same as it was with grass.
This can be done by renting or hiring a professional grading machine, which will effectively scrape the grass out of existence. Again, the result will be a smooth surface a few inches deep in which to place a barrier and then gravel.
This method will definitely not kill off grass or weeds but will clear away enough for a good start and will leave you with a level surface for your rock. Till the grassy area down 4-5 inches, then use a garden rake to remove as much grass and roots as possible and level the soil.
Spray the area with a weed killer or cover immediately with a barrier to prevent quick regrowth. You may need to add a border of some kind, as the gravel may initially rise above any surrounding walkways or driveways.