I have these stones (formerly from a garden center and on top of weed-suppressing fabric in a flower bed for 10 years) and I'm wondering if I can just fork them into this soil. The soil currently looks to bereft of stones presently.

Good idea or bad idea?

Stones: enter image description here

Soil: enter image description here


3 Answers 3


Adding a small amount of grit won't do any harm, but it won't do any good either.

If you are serious about improving the quality of clay soil using grit, you need something like 500 pounds of grit per square yard (250kg per square meter) to have any real effect on the depth of soil that will be cultivated. To make a real difference, you need to get the proportion of clay particles in the soil down to about 20% - hence the huge amount of grit required to do that.

Of course that is completely impractical except for commercial landscaping.

More practical alternatives are adding lime to coagulate the fine clay particles (but check the soil pH first - not all clay soils are naturally acidic) and adding lots of organic matter. IF your clay is not acidic, you can use gypsum instead of lime - many commercial products sold as "clay soil improvers" include gypsum, not lime.

Clay is often rich in nutrients, but improving the texture with lime tends to lock them up so that they are not available for plants. Hence the old farmer's saying in my part of the UK: "Lime and lime and no manure, makes fathers rich and children poor". ("Sustainable agriculture" isn't a new concept!)

  • I remember an article many years about trucking lime to farmers fields to rejuvenate the soil. Unfortunately that's all I remember. I maybe have 150Kg of that grit, and a bed 4m x 80cm - so harmless but won't improve the soil enough.
    – paul_h
    Commented Sep 30, 2018 at 18:47
  • Trucking in lime to REJUVENATE soil? I sure as heck hope those farmers did a pH test and that that soil was horribly acidic. How funny. I do know a dude, a hippie actually, that became rich and famous because he convinced rich people to buy his SOIL. Full of pea gravels, sands, whatever! In my very educated opinion, a total farce. When someone actually knows about soil science, botany, micro/macro soil organisms, decomposition, natural ecosystems...that someone would never try to make BETTER SOIL. That someone knows how to manage the indigenous soil. All soil is great soil.
    – stormy
    Commented Oct 4, 2018 at 23:19
  • Do you know what it is that improves soil FOR PLANTS? It is not gravel, grit, gypsum, lime, water...add rotation and if you have clay soils, you will have concrete. Us humans trying to make soil better without knowing the science are simply on a path that will cause more problems and cost more money.
    – stormy
    Commented Oct 4, 2018 at 23:22
  • @alephzero Adding lime is not to coagulate the clay soil particles. It is ONLY to change the pH, to 'sweeten' the pH taking it upwards from acidic to more alkaline. Clay soil. They are the tiniest rocks that make up soil. The tiniest and they are also flat. Highly electrostatic. Clay soils hold onto chemistry better than silt, loam, sands. Clay holds onto water better and longer. The only way to make ANY soil better THE ONLY WAY is by adding decomposed DECOMPOSED organic matter to the surface of the soil. Adding anything else is contraindicated by the Master Gardener Community.
    – stormy
    Commented Oct 4, 2018 at 23:26
  • Why do you think your soil is bereft of stones or rather that is a bad thing? No one who knows what they are doing in the garden world adds gravels, grits, pebbles to their soil.
    – stormy
    Commented Oct 5, 2018 at 0:10

Bad idea.

  1. Stones or gravels are serveral orders larger than soil particles, so it would not change, particularly here, improve your soil physical structure meaningfully. OTOH, addition of stones (those as shown in your pic) would definitely increase the difficulty of tilling the soil.

  2. Your soil, from the picture of it, looks quite "loamy" to me, i.e. the best soil texture you strive for. If any thing, more compost never hurts.

  3. Soil texture can be quickly tested by forming a ball: when the soil is in moderate moisture condition, pick up half handful of soil and try to form a ball. If it can easily form a ball, and then can be easily broken up, then cograts, you have really good soil. Easy to form, but hard to break, then too much clay, your soil needs more compost or similar stuffs. Some futher reading here: Improving Clay Soils

  • That soil might be fairly dry clay. I added 40%, by volume, sand to my silty clay, plus lots of organic matter. Stones will just irritate your rototiller. Amendment is a major job. I didn't choose tons of sand because I like shoveling. I chose that because that's what it takes to work. Commented Oct 5, 2018 at 15:14

Nothing should be added to soil. It would be nice if your soil had been made into a 'raised' bed without using wood or concrete on the sides.

Guess what concrete is made from? Clay, aggregate such as your stones, sand, gypsum, lime when it needs more heat and water and rotation! Rotation is what shouldn't happen to clay soils ever. Clay are tiny particles of rock and they are flat. Their tiny flat surfaces are highly electrostatic and water and rotation will make these particles stick together and literally make brick, concrete.

This is a picture of my first year garden in Zone 3 with caliche clay. Raised beds, decomposed organic matter on top of the surface, trenches to direct the water. This is the soil they make bricks from. Total clay on top of shale and sandstone. No additions of anything to the clay, no grit, no gravel, no gypsum...nada. pH was boosted just by the decomposed (the magic word) organic material. Every year the soil gets better. Up to a certain point then one needs to quit adding decomposed organic material or at least hold off for a year. Too much of a good thing can be a very very bad thing.

garden in caliche clay first year

You soil looks great. Yummy. Soil by the way rarely has 'nutrients' for plants. Rather 'chemistry' for plants with which to use for photosynthesis where plants make their OWN nutrients, food.

Your biggest problem right now is that soil up against that brick. Pull all soil, gravels, mulch away from your foundation. Try oh try to make some sort of a swale a soft ditch (6' wide 1' deep) to collect water and make sure all water flows AWAY from your foundation. I am not kidding.

The only way to improve ANY soil is by adding decomposed mulch to the surface. The soil organisms need this stuff for energy and they are the ones who mix the organic matter into your soil perfectly. No rock, no gravel, no sand, no gypsum, no peat moss...NADA. This is a picture of how all our beds for plants; ornamental and vegetable should be made. My opinion of course, grins! This no till and no fertilizer propaganda needs to be dumped as gardening techniques.

Note the trenches at the bottom. These beds will never again be 'tilled' or 'rototilled'...I just clean out the trenches once a year and I am ready to plant in the spring.

I most certainly add fertilizer, sparingly and cautiously! And always I cover the surfaces with decomposed organic matter (purchased bales) for the winter. I did an awful lot more of surface covering with DOM during the first year but there comes a point where too much of a good thing becomes bad. Notice the difference in soil from the paths?

I use these once double dug beds for all kinds of soil to include Caliche Clay. Pure clay that turns to snot when it gets wet. I dearly miss my clay soils. All soil is great soil. One just needs to learn how to manage the type of soil they have once they know what type they have. Have you done the mason jar and water thing?

Update: I just have to say, once again, that we humans can not nor should we try to make 'better' soil by mixing anything into the soil. Double digging to make the original bed is the most work we humans should do...well, adding decomposed organic matter to the surface of the soil! Anyone who thinks we humans know best and adds what they think is for better drainage or whatever is just uninformed. What I advocate is the simplest, most sure way to grow any plants. Gee, hate to be so bold, but until someone educates me that there are better ways to grow plants, and sadly that has not happened, the basics are real and necessary.

Adding gravels, pea gravels, sand, gypsum...to our soils and mixing it by hand is off the charts unnatural. The extremes of gardening, are being promoted. Learn about soils, soil life, how in nature soils are made better. What plants need and if anyone says 'plant food' you need to go back and learn why it should not be called plant food! When humans eat more food than we need we get fat and unhealthy. Plants make their own food. Fertilizer, mulch, compost is NOT FOOD for plants. Adding gravels, sand, rototilling to surface level soils is a waste of energy and not at all conducive for plant health.

volcanic pumice beds 2 years old

  • The wall it is against, is a boundary wall, not the house wall / foundations. Thanks for your comments
    – paul_h
    Commented Oct 1, 2018 at 8:19
  • This looks like something you want to protect even if it isn't your home or foundation. Soil on brick like this will ruin this wall. To test drainage in a very basic way, just throw a cup of water on the soil. If that water heads towards any concrete, any foundation, any structures at all that area needs to be resurfaced until the water flows away from structures. All structures. You are very welcome Paul!
    – stormy
    Commented Oct 2, 2018 at 4:54
  • I just reread your question, Paul. You said you use weed suppressing fabric? Please stop using that stuff. It was never meant for weeds, it was just another avenue to make more money off of this landscape fabric. This landscape fabric was ONLY made to put down beneath weight bearing gravels so that the gravels did not sink to be replaced by the fines. This stuff does nothing to stop weeds. It does create major problems for your soil's health and profile.
    – stormy
    Commented Oct 2, 2018 at 23:26
  • the soil has been against that boundary wall like that for 38 years. And yes, slate cippings on top of the weed suppressing fabric, with garden center plants poking through. I can 100% assure you from multi-year experience that weed-suppressing fabric totally stops weed growth. I'm in the UK (where there is also several million miles of brick 'fence' by the way) and maybe the materials used here for that weed-suppressing roll is different to the US.
    – paul_h
    Commented Oct 4, 2018 at 9:08
  • Hey @paul_h I hate to say this, please forgive me, but any type of material on top of soil other than decomposed organic material will only cause you problems not to mention helping in anyway with weed control. This is MY world, Paul. What you are seeing is only on the surface. This fabric was never ever meant for weed control. It was made just to stop the fines from percolating up into the larger pore spaces of gravel. I can assure you that weed fabric is a huge no no. I wish I had a black board and you in the audience to explain the WHY.
    – stormy
    Commented Oct 4, 2018 at 23:07

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