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Container mix experiments are going well, but am not liking the results. (have managed to kill off or severely would several plants in the process. (my bad treatment of very young plants with not much for roots and no energy reserve).

Next step in the mix experiments is "builder's sand".

The stuff I can get easily is advertised as "Washed and graded coarse sand / Use as a paver and flagstone underlayment"

Texture of the stuff is sharp edged grains of a good mix of sizes. Grain size ranges form almost super fine aquarium gravel down to silica dust. (Looks and feels like the stuff you mix with gravel and portland cement to get concrete.)

Should I use a metal window screen or similar and screen out all the super fine particles and 'dust' or just leave them in. Can't get away from the idea that the 'dust' and fine particles are going to clog things up more than they are going to aid in increasing drainage.

Basically, I have no idea of how the sand mixed into the mix aids in drainage. It just sort of looks like filler.
Is fine, uniform, round grain "play" sand better or worse?
Is variable grain size important?
What are the cut-off points before the grain size is too big or too small?

Sand is heavy. How do you add it to a mix and keep the mix light?
Is this just one of the trade offs?
You add just enough sand to get the drainage you need and deal with the density/weight problem?

Thanks much.

Builder's sand is what you get at the hardware store in bags or in bulk from a concrete supplier to make cement. It is coarse grained. It is heavy to use in a potting mix because it will weigh down the pots but it is a good additive to the soil in a raised bed or to lighten up clay soil.

Roughly equal parts of clay, sand and silt will result in the best combination or loam texture of soil. It drains well but is able to hold together and hold on to moisture but still be easy to work. Adding organic matter and particles of varying sizes and shapes keeps feeds the soil organisms and feeds the soil. It also loosens up the soil and leaves air spaces in the soil for plant roots and soil organisms to breathe and water to be held in or pass through. You want a homogenous soil that is well mixed up with a variety of compononents. If everything is the same shape or the same size. It will eventually pack down and become recalcitrant. Things like compost is always breaking down so you have to keep adding more, but it is best to vary your sources of compost so you have a good variety of textures and nutrients to balance out the soil. How much you add of anyone material depends on what you are starting with. If you start with a heavy clay, then more sand is added. If you have a sandy soil then more clay is added. If you have river silt, that's pretty good, adding organic matter to that will loosen it up and add air space between the small particles.

Soil is complex. It has to do with texture, composition, nutrient holding capacity (CEC- cation exchange capacity), pH, salinity, how well it drains, and the dominent biota.

https://articles.extension.org/pages/544 ... components

I killed, yes I just typed killed, several hundred bloodgood Japan maple babies before I knocked off with fine particle soil.

When you are finally tired of killing off plants go to bagged gran-I-grit grower sized grit. You can get it at any Blue-Seal feed store.

Take all the time you want thinking about this.

Thanks for the responses.

Am going to take that as a “Yes.” If I use that sand, screen out the really fine stuff and dust.

Imafan 26, Thanks for the link and explanation. That triangle chart really helped. I get the balance thing and realize the container mix is a balance of trades offs. The big stumbling blocks for me are limited first hand experience and that I have really pitched the learning curve against myself.

Basically, I am not going to be comfortable with this until I know and understand how the core components work together to provide a predictable outcome, and I can alter the balance of the core components and have a very good idea of what the outcome will be.

Tomc, you mentioned “road grit” in another thread and I went looking for it. Everything I found had some kind of chloride or ice melt stuff in it. So I stopped looking. If I can buy it in bags at a blue seal place, I will definitely look into it.

Most importantly I know know I am looking for 3/32” - 3/16” particle size. That puts things into a scale I 'get'.

Worse comes to worse, I know an aquarium store where I can get 50 lbs bags of irregular shaped, rough edged, 1/8” 'natural', aquarium gravel. Not sure what stone it is, but the color varies from light brown to almost white to light grey.

I just learned that lesson about too fine a soil and will loose 1/3 or more of the strawberry plant I tried root of a whim late this fall. I only need 12 and I started out with 50 culled to 30, killed maybe 10 or 12 so far.... so I should be good for the 12 I need.

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Since I didn't get what I wanted out of my first mix experiment. Time to re-think, add in what I have learned, design and perform the second mix experiment.

Still fighting with this one - mostly on the supply side and a little on the concept side.

Have called the area quarry kinds of places and landscape supply places. Biggest issue is transport of large quantities vs the quantity I need. Am looking for maybe 25 gallons and don't really have access to a pick up that doesn't have perfect paint in the bed.

Aquarium shop I was counting on as a back up changed hands and directions a while ago - no more 50 pound bags of #2 to #10 morey sand at reasonable prices. Chicken grit falls in line with this that is is just more than I am willing to spend 25 gallons or so of drainage material for mixes. Not positive, but am guessing I wil need at least 3 if not 5 50 pound bags for 70 - 75 gallons of mix.

Tried screening the fines out of "builder's sand" and that looks promising as a material, but there is a +70 % loss per bag. (Did end up with a nice little supply of fine sand blasting media though!). Am screening through basic window screen.

Did remember I had about 100 pounds or so of #4-ish morey sand in the bottom of a stored 125 gallon tank. That was a nice find but not going to be fun to clean..... did the evap method of tank draining on that one and know there is calcified build up in there and aquarium salt too.

Can't get anything larger that #50 sand from pool supply places which is about where "play sand" measures up. "Play sand" did poorly in the drainage experiments I did with it... seemed to clog things up more than anything. Which convinced me to go with larger grain stuff and to screen the builder's sand.

Biggest goo thing I have accomplished is now I have little zip lock bags of material to bring with me when I go looking for the stuff. "Hi, I am looking for sand somewhere between this stuff and this other stuff..."

Am still not getting the sharp edged stuff is better than the rounded stuff. Sharp edged, irregular grain stuff (chicken grit / Ottawa sand) packs in better and locks together better, hence being used in concrete and setting pavers and the like. Seems like this would be a detrement to container soil. Morey and and the round grain stuff can't pack together and will also adjust to pressure shifts and is used in wells and that kind of thing because water flows easily though it. This seems like it would be better for container mix.

Am kind of at a loss looking for an affordable supply. Am thinking I may have to wait till spring and screen and wash the local glacial till I have. (Did find out that the wet sponges through a food processor with the grating plate does make a good, light. moisture retainer for mix. Looks a little odd but works.)

O.k. Why are you sifting sand? Coarse sand is fine as long as it is clean, you should not have to sift it. Here I can get cinder and pea gravel from a place that sells tile and concrete. They sell sand, cinder and gravel in bulk or by the bag.

Sifting soil here is done to make it soft, but if you sift it fine, over time it packs down very hard (it is clay after all) because the particles are all small.

While you don't want boulders in your planting area, you do want different particle shapes and sizes so they allow for more air space. The air space in the soil is where the roots grow, air space provides a place for water to be held for a brief time instead of running off and air space adds fluff to the soil. Unless you are planting root crops like carrots, the soil does not have to be very fine. Very fine soil will be more packed and when it hardens will actually make it harder for plants to grow. Fine soil will become water logged quickly since the air space is smaller especially if drainage is poor.

If you are growing in containers not planting beds, it is better not to use very much soil in a container. Soil behaves differently in a container than in the ground. Some people do add soil to their container mixes but it is usually a very small amount. Soils in containers pack down faster. Smaller containers dry faster and unevenly from the outside in. This usually leads to contraction and the soil pulls away from the sides and the water flows around the root ball and the plant dies of thirst. Soil in containers are more expansive than potting soils. Soil expands and absorbs moisture and there is less air space for the roots. Expanded soil particles lose water slowly so you have to be careful with watering or the plants will rot.

If you look closely at soil, you will notice that the top layer of the soil contains the most organic material (plants, roots, leaf mulch, compost, etc) The farther down you go the soil turns a lighter color and it is more compact. Most of the roots will be in the dark layer and very few will be down in the lighter layers because most of the nutrients, air and water is on top. The top is not just dirt, it is a mix of the soil and organic matter and the pieces are of different sizes and composition.

If you are planting in containers, the best soil mix will be a soil less mix. Mel's mix works for containers and in ground beds
Mel’s Mix
1/3 vermiculite
1/3 peat moss
1/3 compost (from as many sources as possible)
This is done by volume. My garden beds were each 4’x4′ and needed 6″ of mix to fill them. 4x4x.5=8 cubic feet of Mel’s mix. I did three boxes, so I needed 24 cubic feet of mix, 8 cubic feet of each item. Now, this amount did fill my boxes initially, but as I watered and the mix settled, I added more compost.

Notice there is no soil in this mix, no clay or sand.

I may have confused you. Ideally a loamy soil is what you want, but it is not what most of us have. That is what the soil triangle is trying to depict. Maybe this publication will clear things up.
https://puyallup.wsu.edu/wp-content/upl ... ents-2.pdf

If you are working with the soil in the ground, you need to know what you have to start with. The best way to do that would be to get a soil test. The soil test will ask what you are growing. It does not ask if it is a container mix. Most soil tests will assume you are growing in the ground and your native soil then needs to be taken into account. The soil test results will tell you how much of each type of amendment or fertilizer you need for what you want to plant. If you want organic advice then you have to ask for organic recommendations. Most recommendations will be for synthetic fertilizer unless you ask for organic.

If your soil drains poorly then the easiest way to fix that is to grow in raised beds and not to pick the lowest point on the property to site your garden.

If you are creating a soil mix for a SIP container, you don't really need to use soil and there are sites that have already worked out the formulas for how to set up and the type of soil mix you need. It will be more akin to a well drained potting mix and will not contain soil.
https://albopepper.com/sips.php
https://albopepper.com/soil.php

If you are doing SIPs, there are basic requirements the container and the soil mix need to meet. Wicking beds have similar requirements and issues. Because it is a contained system, salts build up over time and the water logged media at the bottom becomes anaerobic and fungal dominant which can cause problems for some plants that are prone to root rots and fungal diseases. Those plants are not suitable for SIPS. Because it is a contained system salt and fungal issues build up over time so I only use sips for annuals that use a lot of water like tomatoes, cucumbers, peppers, and some herbs. I would not use SIPs for any plants that don't like constantly wet soils. I replace the soil after each crop and sanitize the container with bleach.
https://www.thegardenacademy.com/Self_Wa ... iners.html
https://deepgreenpermaculture.com/diy-I ... struction/

Haven't bee able to find bags of #10 to #6 sand anywhere.

Am sifting the sand I have to get the fine particles out of it. It is labeled as “all purpose sand”. Looking to have just the larger, irregular sizes and shapes. What I have found playing around with mixes is that the “fines” in sand really clog things up.

Thanks for the descriptions and the links.

(Am an ardent pragmatist. Have to look at all the components of something and see how they work and work together before I am comfortable with it.)