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PunkRotten
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Why can't garden soil be used as potting soil?

Hello,


How come on bags of garden soil they say not for containers? My guess would be that they do not contain materials that are good for drainage. I have used garden soil in pots before and have not noticed any problems yet. But I would like to know the reason behind it.


There is a few things I would like to put in pots but I only have garden soil. And I don't feel like buying a bag of "potting" soil. Help is appreciated.

Thx

CharlieBear
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Many people do use it from time to time. Not recommended for pots in part because it is too heavy to lift in a pot of any size. You are partly right it generally contains not vermiculite or perlite or things like coir or peat moss. Potting soil also often has fertilizer in it, I don't ever buy that type. Some bags of "garden soil" are little more than forest waste products that are meant to be worked into existing soil that is a low spot etc and is not soil at all. Also, often the stuff is simply not serile enough to be recommended for starting things in. If you mean your own garden soil from the backyard, some folks do use it mixed 1/2 and 1/2 with their own compost, with different levels of success. I hope I have properly understood you question.

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Kisal
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Because the structure of the soil, due to the size of the particles, inhibits rapid drainage. Garden soil usually contains too much clay to work in containers. The shape of clay particles allows them to fit tightly together, preventing water from draining away and air from entering. Both air and water are needed to enable plants to grow healthy root systems.

Excess moisture in a container can drain away only through the hole or holes in the bottom of the container. It can't spread out horizontally very much due to the contaoner's sides. In open ground, however, excess moisture can spread horizontally without constraint, as well as down into the depths of the soil.

Potting mixes, whether they contain any actual soil or not, have a coarse structure. If soil is used as one of the components, it should be high-quality topsoil that contains a lot of humus, which is partially decomposed vegetable matter. You can add this to your own potting soil recipe by adding your homemade compost, but you'll will want to avoid sifting your compost too finely. Larger pieces of bark and other materials create spaces to allow the water to drain away quickly and air to enter.

In addition to compost and topsoil, other components can be materials like coarse sand or fine bits of gravel, perlite, peat moss, etc. added in varying proportions to produce the correct pH for the species of plants that will be grown.

Does that help? :)
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PunkRotten
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Yes thanks a lot for the explanation both of you. Lets say I use like 1 part of garden soil, 1 part of dirt from my yard (clay soil) and 1 part play sand would this be alright? How about aquarium gravel or pea gravel?

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applestar
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I think you'll want some humus in the mix. I typically combine home made compost with GOOD topsoil from my garden (usually from under pile of leaves or the woodpile) and sand (play sand, all purpose, or patio paver). I also add dolomitic lime, rock phosphate, ground oyster shells, greensand, alfalfa pellets, etc.)

For the compost, I use larger screen for large containers and smaller screen for smaller containers so there are chunks to vary the soil structur for better drainage.

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I use garden soil in most of my large flower planters. To make them lighter I place a few empty bottles with lids on at the bottom of the barres! I also use some of the styrofoam from broken packing materials or any type light material at the very bottom and it really makes it easier to lift! I also use the garden soil that is 6 inches below the surface since it ha less weed seeds in it! Leaves are always good at the bottom with some sand!
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I usually strain the top 6 inches of garden soil and mix anything that makes it better that I have even sand! You will be suprised how nice strained garden soil can be especially it the strainer is of a medium grid not to fine! Even a plastic or metal sifter or wire container can sift the soil right from the top of the pot!
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Kisal
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I don't think the recipe you posted would do well. You can experiment with different mixes, if you like, until you find one that works well for you, of course. I don't find the weight of the container to be an issue, since I put them where I want them before I fill them with the growing medium.Filling the bottom with rocks or other stuff is akin to planting the plants in too small of a container. I prefer to fill the entire container with soil, to provide the roots with plenty of growing space.

I no longer mix my own growing media. By the time I bought vermiculite, perlite, the proper types of sand and gravel, the humus and compost, and all the other stuff, it cost me more money that just buying good bagged soils. (It also required much more storage space. :lol: )
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froggy
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Yep, same here - i get cactus soil for my small planters, and the big ones i use potting soil. a bag of perlite is almost as much as a same size bag of soil... besides, i am lazy. i buy orchid mix for my orchids and tropicals (i found one that doesn't cost an arm and a leg, and it consists mainly of penny size bark chips) and i mix that in for some of my (potted, not yet bonsai) trees as well...
;)

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I put my planters in the greenhouse for the winter that is why I like them lighter! 200 pounds of soil in one ot is too expensive soI use garden soil place a good planting media in the top several inches to stop any weeds! big planters you can almost put anything in the bottom like leaves or composted material!
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jal_ut
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Re: Why can't garden soil be used as potting soil?

"Yes thanks a lot for the explanation both of you. Lets say I use like 1 part of garden soil, 1 part of dirt from my yard (clay soil) and 1 part play sand would this be alright? How about aquarium gravel or pea gravel?"

I think this would work. Skip the gravel. Hey, give it a whirl.
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jal_ut
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Re: Why can't garden soil be used as potting soil?

Soil, according to Wiki: Soil is a mixture of minerals, organic matter, gases, liquids, and countless organisms that together support life on Earth.

Soil according to Jal_ut: That miraculous thin covering of the Earth where plant roots reside.

That stuff that comes in bags and is called soil, is likely not soil at all but a collection of wood scraps and other humus.
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jal_ut
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Re: Why can't garden soil be used as potting soil?

Mother used to take me up the canyon and have me fill a bucket of the soil that was under the canopy of the maple trees. It was black and mellow and seemed to be loaded with organic matter. Decaying leaves I suppose? Now days one would get tossed in jail for trying that? :)
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Re: Why can't garden soil be used as potting soil?

Some people like to use dirt. It is heavy and contracts when it is dry. It can work but soil behaves diferently in a pots. I just have better results using potting mix. I like MG potting mix but not the moisture control. All pottng mixes are not created equal. Super soil used to be good, but it contains too much compost now and it just kills everything.
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Re: Why can't garden soil be used as potting soil?

The soil in my garden is mostly clay. Yes, stuff grows well in the garden but I'm not about to try using that stuff in a pot. I buy bagged potting mix and add compost, rabbit manure, and fertilizer. My clay gets too hard to break up without a lot of work. Bagged potting mix always stays loose and friable. Easier to weed, easier to plant, easier to harvest. But it also drains much better so I can plant in the spring monsoon season when water is standing an inch deep in the garden. Yep, you can say I'm a lazy gardener.

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Re: Why can't garden soil be used as potting soil?

Most don't need to use garden soil if you simply have a mulch pile. Takes about 1 year to get a good leaf mold. Next, you must soak mulch in water for 1.5 hours to destroy insects and their eggs. I'm at the age in life I have just starting learning to grow plants in water and starting to have a little success...less work.

imafan26
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Re: Why can't garden soil be used as potting soil?

I made a mistake once and put garden soil in the container instead of potting soil. The bags looked alike so it really was an honest mistake. The first thing I noticed was the lack of perlite. The second was how coarse it was and how heavy it was. I tried it anyway and the pots did not drain well, the water pooled on top and when the pots dried it contracted and the plants stayed wet for too long, eventually they yellowed and died. I guess it did not have any fertilizer either. In fact it acted a lot like compost.

I usually make a custom mix because I water a lot and I live in an area where seasonal rains can come all day every day for a week so I need to have a year round mix that drains well and dries fast. It means in the dry season, (which should be now but it is not) I have to water more or double pot.

I in the wet season I use 50/50 peat moss and perlite a handful or two of vermicast if I have it in a 5 gallon bucket + a couple of tablespoons of osmocote as a starter fertilizer.
In the dry season if the plants are drying too fast I use a 60/40 mix of peat moss and perlite, but I will usually only use it on plants I plan to keep in pots only temporarily. I am never going to get around to repotting before the rains come again so it is better for me to water more when it is dry and double pot rather than have the plants drown when the rainy season comes.
I have extra holes drilled in plastic pots so they drain better, double potting blocks the holes, I just have to remove the outer pot before they drown.
For succulents and orchids which cannot tolerate wet feet, I plant in terra cotta pots, baskets, pots with extra holes in them, and media is usually black or red cinders or for some orchids and bromeliads no media at all. Eventually the orchids will attach to a porous pot and they can be watered every day that way. In the rainforest they don't grow in pots, they grow in trees with their roots hanging out in the air so even though it rains every day in the forest, the roots have ample time to dry.

The succulents pose a bigger problem for me so I have to choose the ones that can take more water and keep them where none of the sprinklers can reach them. If it rains for a long time, day and night, I have to bring them in to the patio so they can dry out. I keep my lavender by the patio under the eaves so when it rains it does not get rained on directly and the water coming off the roof falls outside of where the pots are. Lavender leaves will turn black and the plants can die if they get too much water. I am having problems with my lavender. I used to grow them better. It may be my mix. I am usuing a higher percentage of perlite to keep them drier but I am still having some of them die Anybody have a good soil mix for lavender?
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tomc
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Re: Why can't garden soil be used as potting soil?

PR, a mix of half sand and half potting soil would be better. Its air that most long term potted plants lack. I can direct you to bonsai growers who are using 1/2 chicken grit, and 1/2 pine bark mulch with perfectly happy trees.
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