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Everyone seems to be affraid of garden dirt for a indoor container because of bugs and weeds! Just take a quart plastic bag and put a pint of dirt and lay it flat half zipped shut& heat it for a minute till it fills a little hot and its done! I like to put a layer of play sand mixed with pea gravel and half fill any [pot and then the rest of the pot I fill it with the microwaved garden soil! If you ever make a outside fire take a few gallon metal paint bukets and fill them with garden soil put them in the fire and you have the best container or seed starting soil money can buy! Take out the worms first for fishing or put them back after the soil cools! I remember one year I planted some tomato seeds in boxes and put a dozen small worms in several of the 6 inch deep boxes. The boxes with the worms had better looking and bigger plants in the same time as the other boxes!!

I don't object to garden soil for containers because of the potential presence of insects, but rather, because it doesn't drain rapidly enough.

Microwaving is a poor method for killing insects, whether they're in soil or just running around loose in the microwave. It's more effective to moisten the soil, place it in an oven proof container, cover it tightly with foil, and bake it at 225º for an hour. Of course, the drawback to that method is that you end up with sterilized soil, having killed off any good bacteria it contained. And it still won't drain well enough or admit enough air to the roots to work well in the confines of the average indoor plant container.

I think the best method for killing insects would be to seal the soil in a container and place it in a freezer for about a week.

It's not terribly difficult to mix a good container soil at home, but I'm partial to soilless mixes for indoor plants. They are less prone to fungus gnats and other problems common to indoor plants. Also, the bags of the various components necessary to create a good potting mixture must be stored somewhere. Not all of us have space for that.

Good points! That is why I put sand and pea gravel or styrofoam beads with the sand in bottom half of the container! Sand is cheap an works with most soils and the roots seem to love it!

I like to provide a container full of actual growing medium for my plants. I have found no advantage to using rocks, broken crockery, sand, or anything else in the lower part of the container. The roots like it very much.

When the bottom of a container is full of rocks or anything other than soil, the roots will still grow down into that layer. When the plant is pulled or dug at harvest or when it's time to repot, whatever is in the bottom of the pot comes up with the roots and gets mixed in with the rest of the soil. Once that happens, of course, the material is no longer on the bottom of the container, where it might help with drainage. Being mixed into the soil, it can interfere with root crops, such as carrots. For that matter, it can interfere with any plant's roots. I don't know of any gardener who intentionally gardens in rocky soil. The only way to correct the situation is to remove all the soil from the container and sift out the debris, then refill the container from scratch.

I might put rocks or sand in the bottom of a container if I needed to add weight to a container that would be exposed to high winds, or to stabilize a tall, top-heavy plant that might otherwise topple over.

Kisal wrote: Microwaving is a poor method for killing insects, whether they're in soil or just running around loose in the microwave. It's more effective to moisten the soil, place it in an oven proof container, cover it tightly with foil, and bake it at 225º for an hour. Of course, the drawback to that method is that you end up with sterilized soil, having killed off any good bacteria it contained. And it still won't drain well enough or admit enough air to the roots to work well in the confines of the average indoor plant container.

The other drawback to the oven method, since I have tried it, is that it stinks the whole house up! The smell of baking soil is pretty bad.

And I agree with Kisal re the drainage issues and that if you bake/ microwave your soil, you have killed off all the microbial life in it. To me that microbial life would be the best reason for using garden soil in the first place.

You can make your own potting mix, but it really entails assembling all the ingredients that the commercial folks use... peat moss or coconut coir, perlite/ vermiculite, sterilized compost, etc. I've done it in the past and decided for me it really isn't worth the hassle, the expense, storing all the components etc. If you buy your potting mix in bulk, it is actually less expensive than buying all the components.

rainbowgardener wrote:The other drawback to the oven method, since I have tried it, is that it stinks the whole house up! The smell of baking soil is pretty bad.

Ah, yes! How well I remember the very pungent odor of roasting dirt!

Althugh I mentioned micro waving soil I usually just use the soil directly out of the garden but take it about a foot under the surface to eliminate the weeds! I then put a small layer of sand and put the seeds on top the sand and cover the seeds with a few inches of seed potting soil! I cover the box with a window or plastic till the seeds start to sprout! My greenhouse has only solar heat so it takes about 10 days for the seeds to sprout especially Tomato seeds! I do get a few weeds but not many and the plants are healthy!