Question on Organic Gardening Soil:

[mod mom]

This year I moved my garden from the ground level (mainly due to my 2 big dogs hopping the fence and stealing the veggies) to my flat roof. I bought fiberglass posts and used miracle grow organic garden soil in the pots. The veggie plants appear to be doing great. Today while I was transplanting some window basil plants to a larger pot out on the roof, I noticed the bag of organic garden soil says "not for containers". Does anyone have any idea why this soil would not be ok for pots? It's intended use is for tomatoes, vegetables and herbs.

[Gormy Cuss]

1. Probably because it's too heavy.

It sounds like you bought a planting mix, intended for amending a garden bed, as opposed to a potting soil. Potting soil mixes usually include something that keeps the mix from compacting (vermiculite, moss, etc.) Potting soil also weighs less and is preferred for very large containers on decks and roofs.

Over time your container soil will compact but for a while it will be just fine. The basil plants can be amended now buy lifting them and scooping out some of the heavier soil and replacing it with potting mix. If you have a short season you may not have any problems at all this year. The tomato plants should be fine -- I made the same mistake when I was growing them in 5 gallon containers and I had plenty of tomatoes.

Just be sure to dig and turn the soil next year before you plant and if you need to add some soil, add potting soil or a seed starting mix.

[mod mom]

2. Thank you for your information and advice.

[theHandpuppet]

3. I have also used this soil

But when I use it for pots I add some extra vermiculite for better drainage and aeration and a layer of aged straw as the bottom layer. (Aged straw = straw which I have scattered from its bale and let to age over the winter season. I've also substituted aged cornstalk leaves left over from last season's Halloween displays, but for small pots you'll need to chop/tear them into small pieces. Both have worked for me.)

BTW, this is the first year I've used the Miracle Grow organic soil and I still have mixed feelings about using it. I've always made up my own soils, with a good grade top soil, composted cow manure, my own home compost and glacial rock dust. Unfortunately I was unable to get the composted cow manure early in the season (Black Cow is the brand) so I used some of the Miracle Grow soil for some of my containers. I would swear by Black Cow top soil and composted cow manure; if it's not available I simply won't buy another brand. The difference it makes in my garden is astounding.

[Kolesar]

4. IIRC, vermiculite actually holds water--what one wants in a container...

...where the soil can dry out fast on a hot day.

I am curious about your glacial rock dust. At my last house, the soil was clay that was called "glacial till". It was quite impervious to water. I did not have a garden at that house, but my grass was always quite healthy and green.