I have horribly dense clay soil at my recently purchased house in central Denver. I have read about amending solid with sand and am not sure if this is the way to go as I don't want to disturb the nutrient levels of my soil in my planting bed. The other issue I am having currently is with removing unwanted vegetation from my lawn, i.e. recurrent dandelions (thumb sized roots) and mint. Yes, mint. I'd prefer not to use chemicals and to remove by hand, but the density of the soil is making it difficult. I haven't checked the pH of my soil as of yet as I just moved into the property in November. I'm a native and grew up with this type of soil, now I'm just tired of fighting with it! I'd appreciate any suggestions you have.
Thank you- Julie P.
Denver County Colorado
You are right not to put sand in clay, as this is how concrete is made. The best soil amendment is low-salt compost (those made with steer or sheep manure may be too high in salts). Get a soil test now, through CSU (Google CSU soil test kit) or at a commercial lab.
I suggest you deal with your weeds, first, although there is an arsenal of weed seeds in your soil that can germinate after amendment. If hand-pulling weeds is not an option (can you pay someone? Try watering your ground the day before you pull.), then glyphosate is your least toxic alternative. It degrades rapidly in the soil. Please do not get the kind that "knocks down weeds in 24 hrs," as it contains another, longer-lasting herbicide. Look on the label for no other active ingredient than glyphosate. Glyphosate may be toxic in ways we are not sure of, yet, so wear a mask, nitrile or latex gloves, long pants and sleeves, and take a shower when you're done.
Glyphosate will kill any vegetation, so, if you are keeping your soil, get a narrow water bottle and cut off top & bottom. hold close to the weed and spray gently into the top of the bottle. You can cut some of the mint off and still have it work. Don.t let treated mint lie on your soil, however. This you can pull through a small hole in the bottom of a plastic grocery bag, spray into the bag and tie off for a day. The plant needs to lie there longer so it can send the glyphosate to its roots, but you can remove the bag after a day.
There are such products as "Weed'n'Feed" that will kill the broadleaf weeds and not the grass.
Here is a CSU Extension publication on soil amendments for clay: